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Sintering and microwave dielectric properties of LTCC-zinc

titanate multilayers

Q.L.Zhang,H.Yang *,J.L.Zou,H.P.Wang

Department of Materials and Engineering,College of Materials Science and Chemical Engineering,Zhejiang University,Hangzhou 310027,China

Received 13July 2004;received in revised form 24November 2004;accepted 29November 2004

Available online 18December 2004

Abstract

The effects of ZnO–B 2O 3–SiO 2(ZBS)on the sintering behavior and microwave dielectric properties of ZnO–TiO 2system were investigated as a function of ZBS content and sintering temperature.Densities of the specimens were enhanced with an increase of ZBS up to 2wt.%and then decreased.X-ray diffractometry analyses results indicated that the phase stability region of the hexagonal ZnTiO 3extended to lower temperatures as the amount of ZBS increased.The dielectric properties of ZnO–TiO 2system with ZBS are strongly dependent on the sintering conditions,especially near the phase decomposition temperature.The sintering temperature of the specimens could be reduced to 9008C without the degradation of the microwave dielectric properties.From 9008C,the temperature compensation characteristics occurred as the phase composition changed from ZnTiO 3to two phases:Zn 2TiO 4and rutile.The dielectric constant (e r )increased and Q ?f value decreased due to the phase decomposition.The e r value of 27,Q ?f value of 19,396(at 6GHz)and s f value of 2ppm/8C were obtained for ZnO–TiO 2ceramics with 2.0wt.%ZBS sintered at 9008C for 3h.The low-temperature sintering ceramics powders were suitable for the tape casting process.Also,the material is compatible with Ag electrodes and,therefore,is suitable for LTCC application.D 2004Elsevier B.V .All rights reserved.

Keywords:Microwave dielectric properties;Liquid phase sintering;Microwave ceramics;Multilayer device structure

1.Introduction

Over the past decade,RF multilayer device structures have been developed in order to induce the device size,for which a low melting point flux is frequently added to co-fire the dielectric ceramics with high conductive internal-electrode metal such as silver or copper.Although several types of dielectric materials with good microwave dielectric properties have been reported,they usually needed to be sintered at high sintering temperatures.Therefore,it is necessary to lower the sintering temperature of the dielectric ceramics in order to process the ceramics along with electrode material.Low-temperature sintering of dielectric materials with glass addition have been successfully developed in the several microwave dielectric systems,

e.g.(Zr,Sn)TiO 4,BaO–TiO 2,ZnO–Nb 2O 5–TiO 2,(Ca,Mg)TiO 3,BaO–Nd 2O 3–TiO 2,et al.[1–9].However,the majority of the ceramics systems with glass and/or a mixture of additives offer relatively inferior dielectrical performances relative to those of the high-temperature firing systems.

Golovchanshi et al.reported that hexagonal ZnTiO 3ceramics as a microwave dielectric material could be sintered at relatively low temperature (11008C).The dielectric constant (e r )of 19,the quality factor (Q ?f)of 30,000GHz,and the temperature coefficients of the resonant frequency (s f )of à55ppm/8C were obtained.They pointed out that ZnTiO 3ceramics could be a good candidate for low firing microwave dielectric ceramics [10].Kim et al.demonstrated that the additions of 1–5wt.%B 2O 3were effective in reducing the sintering temperature of the ZnTiO 3ceramics from 1100to 8758C without degradation of microwave dielectric properties [11].However,our previous work found that addition B 2O 3in the ceramics

*Corresponding author.Tel./fax:+8657187953054.E-mail address:yanghui@https://www.wendangku.net/doc/5c12282466.html, (H.Yang).

Materials Letters 59(2005)880–

884

https://www.wendangku.net/doc/5c12282466.html,/locate/matlet

was unsuitable for the tape casting process due to its very large viscosity caused by the free B2O3reacted with the solvents,and the surface of ceramics green tape was rough due to precipitation of the free B2O3out of the solvent.

In this study,the microwave dielectric ceramics based on ZnTiO3was chosen as the host material.To compensate the s f value,TiO2with positive s f value(+450ppm/8C)[12]was added to form a composition of ZnTiO3+0.2TiO2ceramics. Instead of B2O3,ZnO–B2O3–SiO2(ZBS)was used as an additive to promote the sintering of ZnTiO3ceramics.The sintering behavior and microwave dielectrics with different amount of ZBS addition were investigated.Relationships among crystalline phase,sintering temperature,and the amount of ZBS addition were also discussed.The properties of ceramics slurry and green tape and the chemical compatibility of silver electrodes and the low-fired samples have also been investigated.

2.Experimental procedure

Reagent-grade raw materials of ZnO and TiO2with purities higher than99%were used as the starting materials. These powders were appropriately weighed to meet the mol ratio of ZnO/TiO2=1:1.2,and then milled with ZrO2balls for24h in ethanol.Mixtures were dried and calcined at780 8C for2h.The ZBS glass with the composition of60%ZnO, 27%B2O3,and13%SiO2(in mol)was prepared by firing in platinum crucible at the temperature of12008C.ZBS glass frit was milled with a mixture of agate balls in different diameters of7–25mm to an average particle size of less than4A m.The calcined ceramic powders were re-milled for 24h with the additions of ZBS glass powders,and then the mixed powders were pressed into pellets with10mm in diameter and5mm in thickness under1000kg/cm2 isostatically.The pellets were sintered for4h in air subsequently from860to9608C.The crystalline phases were analyzed by X-ray powder diffraction(XRD)using Cu-K a radiation of2h from20to808.The microstructure observation of the ceramics sections was performed under a scanning electron microscope(SEM).The bulk densities of the sintered pellets were measured by the Archimedes method.Microwave dielectric constants e r and the quality factor values Q?f at microwave frequencies were measured by Hakki-Coleman dielectric resonator method using an Agilent8719ET(50MHz–13.5GHz)Network Analyzer. Temperature coefficient of resonant frequency s f was also measured by the same method with changing temperature mainly from25to808C and calculated from the equation: s f?f80àf25

eT=f25?55

eT?106ppm8C

eTe1Twhere f80and f25represent the resonant frequency at80and 258C,respectively.

3.Results and discussion

Fig.1shows(a)XRD patterns of ZnO–TiO2system with ZBS sintered at9008for3h,and(b)with2wt.%ZBS sintered at different temperature for3h.For all the specimens sintered at9008for3h,hexagonal ZnTiO3and rutile(TiO2)were formed.However,with5wt.%ZBS addition,a small amount of unknown phase was detected. The hexagonal ZnTiO3phase was maintained at the sintering temperature(Ts)\9008C.Zn2TiO4appeared as the main crystalline phase associated with rutile and ZnTiO3 at Ts=9208C.At9408C,the ZnTiO3phase completely disappeared.It indicates that the ZnTiO3phase was decomposed to cubic Zn2TiO4and rutile at Ts N9008C, which is lower than the decomposing temperature of9508C reported by Kim[13].These results suggest that ZBS can lower the decomposing temperature of ZnTiO3phase.

From our studies,pure ZnO–TiO2ceramics specimens sintered at11008C for3h had about98%theoretical density(TD=5.09g/cm3,estimated from the XRD pat-tern).The bulk densities of ZnO–TiO2ceramics with various amount of ZBS addition at different sintering temperature for3h are shown in Fig.2.The ZnO–TiO2ceramics

with Fig.1.(a)XRD patterns of ZnO–TiO2system with ZBS sintered at9008C,and(b)with2wt.%ZBS sintered at different temperatures.

Q.L.Zhang et al./Materials Letters59(2005)880–884881

ZBS have attained94–97%TD below9608.For ZnO–TiO2 ceramics with0.5,1,2,and5wt.%ZBS addition,the94%, 96%,97%,and94%of TD were obtained with ease at920, 900,900,and9208C,respectively.With0.5and5wt.% ZBS addition,the density of ZnO–TiO2ceramics increased with the increase of sintering temperature and then reached a saturation value.However,for the specimen with1–2wt.% ZBS addition,the densities of ZnO–TiO2ceramics initially increased with increasing sintering temperature and then decreased.With an increase of the ZBS contents up to2 wt.%,the density of ZnO–TiO2ceramics increased and then remarkably decreased.It has been reported that the sintering aids containing boron oxide promoted densification by liquid phase sintering and then evaporated[14].Addition up to2wt.%and increasing the sintering temperature,ZBS formed a liquid phase which helped to increase the density of sintered body.However,with ZBS addition above2wt.% and too high sintering temperature induced excess pores due to the evaporation of the sintering aid,which in turn, reduced the density of ZnO–TiO2ceramics.

SEM micrographs of ZnO–TiO2ceramics sintered at900 and9408C for3h with several different ZBS contents are shown in Fig.3.The sections of pure ZnO–TiO2ceramics sintered at9608C are porous and the grains did not grow(not shown here).However,uniform grain growth and a reduction in porosity with increasing ZBS amount can be observed for the ZnO–TiO2ceramics sintered at9008C.For ZnO–TiO2ceramics with2wt.%ZBS addition,the homogeneously fine microstructures with almost no pores are observed in Fig.3(c).However,further ZBS addition and sintering temperature increase enhanced the porosity due to the evaporation of liquid phase illustrated in Fig.3(d)and(f), in which these relatively large pores seem to result from the coalescence of originally small pores.The increase in porosity leads to the decrease of density of the sintered body.

Fig.4illustrates the e r of ZnO–TiO2ceramics as a function of sintering temperature and amount of ZBS addition.With1–5wt.%ZBS addition,the e r values increased with increasing sintering temperature and then reached a saturation value.However,for the specimen with 0.5wt.%ZBS addition,the e r values increased monotoni-cally with the increase in sintering temperature.The dielectric constant is dependent on the density and phase constituents.The e r of ZnO–TiO2ceramics with1–5and0.5 wt.%ZBS increased significantly with sintering temperature up to900and9208C,respectively,which is due to the density increase shown in Fig.2.However,with1–5wt.% ZBS addition,further increase in sintering temperature from 900to9208C led the e r values to increase more quickly due to the phase decomposition from ZnTiO3to Zn2TiO4

and Fig.3.Scanning electron micrographs of ZnO–TiO2ceramics sintered for3h at9008C with content of ZBS;(a)0.5,(b)1.0,(c)2.0,(d)5wt.%,and9408C with content of ZBS;(e)2.0,(f)5.0wt.%,

respectively.

Fig. 2.Bulk density ZnO–TiO2ceramics as a function of sintering

temperature and amount of ZBS addition.

Q.L.Zhang et al./Materials Letters59(2005)880–884

882

rutile,confirmed by phase analyses in Fig.1.When the sintering temperature was higher than 9208C,the e r values of ZnO–TiO 2ceramics with 0.5wt.%ZBS addition increased continuously with sintering temperature due to the phase decomposition.The average dielectric constant of hexagonal ZnTiO 3phase and cubic Zn 2TiO 4phase are similar,which are about 22,21,respectively [13].In contrast,the e r of TiO 2is very large (e r =100)[12].Thus,the increased dielectric constants with increasing sintering temperature are attributed to the rutile phase evolution from the phase decomposition.For the specimens with the same sintering temperature,the dielectric constant increase up to the addition of 2.0wt.%ZBS was due to the increasing of density.However,the dielectric constant decrease with 5.0wt.%ZBS may be due to the liquid phase with the low dielectric constant,as confirmed in Fig.3.

The Q ?f values of ZnO–TiO 2ceramics are strongly dependent on both sintering temperature and amount of ZBS addition as shown in Fig.5.With increasing sintering temperature,the Q ?f value is found to increase to a maximum value and thereafter to decrease.For ZnO–TiO 2ceramics with

0.5,1.0,2.0,5wt.%ZBS additions and sintered at 920,900,900,and 9008C,maximum Q ?f values are 11,682,19,822,19,396,and 19,682GHz,respectively.The microwave dielectric loss was mainly caused not only by the lattice irrational modes,but also by the pores,the grain morphology,the densification,and the second phase.The increase in Q ?f value at low temperature was due to the increase in densities and grain growth,and the maximum Q ?f value corresponds to the maximum density.The decreases in Q factors of the increasing temperature above decomposing temperature are attributed to the formation of Zn 2TiO 4,which have lower Q ?f value than ZnTiO 3[13],and the increasing of porosity.

Fig.6demonstrates the temperature coefficient of resonant frequency (s f )of the ZnO–TiO 2with ZBS sintered for 3h at 9008C.The s f values did not change significantly with ZBS content in this experiment.For all samples,The s f values varied range from à3ppm/8C to 2ppm/8C.

In order to investigate ceramics slurry for tape casting,the powders were first mixed with solvents and dispersant in

Fig.5.The Q ?f values of ZnO–TiO 2ceramics as a function of sintering temperature and amount of ZBS

addition.

Fig.6.The s f value of the ZnO–TiO 2ceramics with ZBS sintered for 3h at 9008

Fig.4.Dielectric constants of ZnO–TiO 2ceramics as a function of sintering temperature and amount of ZBS

addition.

Fig.7.SEM microstructure of the upper surface of tapes.

Q.L.Zhang et al./Materials Letters 59(2005)880–884883

ball mill for 24h,and then plasticizers and binder were added and mixed for another 24h to obtain the slurry.The solvents were toluol and ethanol.The dispersant was menhaden fish oil (OA85).The binder itself was polyvinyl butyral (BM-2),and the compatible plasticizer was butyl benzyl phthalate (S160).The tape casting was done with caster (TM-MC-500).The ceramics slurry viscosity was 1200mPa S.Generally,ceramics slurries with viscosity of 1000–2000mPa d S are suitable for the tape casting process.Fig.7shows the green microstructures of the tapes.In the green state,the average particle sizes of ZnO–TiO 2ceramics was around 1A m and the microstructures of the green tapes were uniform and there was no existence of agglomerates.On the other hand,the surface of the green tape was glabrous;the green tape had very high density and tensile strength.

For compatibility tests,ceramics sheet with Ag electro-des were co-fired and analyzed to detect interactions between the low-fired samples and electrodes.SEM analysis revealed no interaction forming new phases after firing,as shown in Fig.8.It is obvious that reaction of low-fired ZnO–TiO 2with Ag electrodes did not occur.Therefore,ZnO–TiO 2ceramics with ZBS could be selected as suitable candidates for LTCC materials,because of low sintering temperature,good microwave dielectric properties,and compatibility with electrodes.

4.Conclusion

The effect of ZBS addition on the microwave dielectric properties and the microstructures of ZnO–TiO 2system

were investigated.The density of ZnO–TiO 2ceramics was increased up to 98%of theoretical density by an addition of ZBS up to 2wt.%.With more addition of ZBS,the density reduced by formation of large pores due to the evaporation of the liquid phase.The decomposing temperature of ZnTiO 3phase to Zn 2TiO 4and rutile decreased by ZBS.For the same ZBS content,the dielectric constant e r saturated at the temperature of phase decomposing com-pletely,the maximum Q ?f values were obtained at the temperature of initial phase decomposition.For the same sintering temperature,the dielectric constant e r and Q ?f values increased initially and then decreased with increasing the ZBS content.The s f values did not change significantly with ZBS content in this experiment.ZnO–TiO 2ceramics with 2.0wt.%ZBS addition sintered at 9008C for 3h possessed excellent microwave dielectric properties:e r =27,Q ?f value ~20,000GHz,s f value ~2ppm/8C.Also,the material is suitable for the tape casting process and compatible with Ag electrodes and,therefore,is suitable for LTCC application.

Acknowledgements

This work was supported by Chinese High Tech Program under grant No.2003AA302760.

References

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Fig.8.Scanning electron micrographs of ZnO–TiO 2with 2wt.%ZBS samples co-fired with Ag in air at 900for 3h.

Q.L.Zhang et al./Materials Letters 59(2005)880–884

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图表与口诀记忆when、as、while的区别

图表与口诀记忆when、as、while的区别 1.图表与口诀前知识关键是比较主从句子的动词，看其动词的持续性。瞬间的理解成点，持续的理解成线。主从关系有：点（点点、点线），线线，线点。点：为瞬间动词，准确地称为“终止性动词”，指动词具有某种内在界限的含义，一旦达到这个界限，该动作就完成了。如come（来），一旦“到来”，该动作就不再继续下去了。瞬间动词：arrive, begin, borrow, become, buy, catch, come, die, find, go，give, graduate, join, kill, lose, leave, marry, realize… 线：为非瞬间动词，准确地称为叫“延续性动词”。包括动态动词静态动词。动态动词：live, sit, stand, study, talk, work, write… 静态动词（状态动词）：情感、看法、愿望等。Be, belong, consist, exist, feel, hate, have, hope, love, want… 兼有瞬时和非瞬时的动词：feel，look，move，run，work，write…，需要根据不同的语境判断。 2. when、as、while的区别一览表【表格说明】：第一个点或者线表示从句谓语动词的持续性特征，黑点表示从句所表示的动作持续短，为瞬间动词，线表示持续长，为非瞬间动词。1~7为主句与从句所表示的动作时间有重合，第8为主句与从句所表示的动作不是同时发生，而是有先后顺序。线线重相并发生，长线” 【主句谓语为非瞬间动词中的动态动词】【记忆：等线动，相并发生，但：【主句谓语为非瞬间动词中的静态动词】【记忆：等线动，

when,while,as的区别

一、根据从句动作的持续性来区分 1.“主短从长”型：即主句是一个短暂性的动作，而从句是一个持续性动作，此时三者都可用。如： Jim hurt his arm while [when, as] he was playing tennis. 吉姆打网球时把手臂扭了。 As [When, While] she was waiting for the train, she became very impatient. 她在等火车时，变得很不耐烦。注意：as用于引出一个持续性动词表示“在……期间”时，其谓语通常只能是那些含有动作和发展意味的动词，一般不能是那些不用于进行时态的动词(如be, seem, love, want, agree, see, know, have 等)，所以下面一句中的while不能换为as： A：I’m going to the post office. 我要去邮局。 B：While you are there, can you get me some stamps? 当你在邮局时，能帮我买几张邮票吗? 若主句与从句表示的是两个几乎同时发生的动作，含有类似汉语“刚要……就”“正要……却”的意思，英语一般要用as(也可用when)，且此时通常连用副词just。且此时，从句一般用进行时，主句用短暂性动词的一般时态。【注意与六区别】 I caught him just when [as] he was leaving the building. 他正要离开大楼的时候，我把他截住了。 Just as [when] the two men were leaving, a message arrived. 就在这两个人要离开的时候，突然有了消息。 2.“主长从长”型：即主句和从句为两个同时进行的动作或存在的状态，且强调主句动作或状态延续到从句所指的整个时间，此时通常要用while。如： I always listen to the radio while I’m driving. 我总是一边开车一边听收音机。 He didn’t ask me in; he kept me standing at the door while he read the me ssage. 他没有让我进去，他只顾看那张条子，让我站在门口等着。但是，若主句和从句所表示的两个同时进行的动作含有“一边……一边”之意时，则习惯上要用as。如： He swung his arms as he walked. 他走路时摆动着手臂。 I couldn’t remember a story to tell the children, so I made one up as I went along. 我想不出有什么故事可给孩子讲了，只好现编现讲。 3.“主长从短”型：即主句是一个持续性动作，而从句是一个短暂性动作，此时可以用a s或when，但不能用while。如：

while、when和as的用法区别

as when while 的区别和用法 as when while的用法一、as的意思是“正当……时候”,它既可表示一个具体的时间点，也可以表示一段时间。as可表示主句和从句的动作同时发生或同时持续，即“点点重合”“线线重合”；又可表示一个动作发生在另一个动作的持续过程中，即“点线重合”，但不能表示两个动作一前一后发生。如果主句和从句的谓语动词都表示持续性的动作，二者均可用进行时，也可以一个用进行时，一个用一般时或者都用一般时。 1、As I got on the bus，he got off. 我上车，他下车。（点点重合）两个动作都是非延续性的 2、He was writing as I was reading. 我看书时，他在写字。（线线重合）两个动作都是延续性的 3、The students were talking as the teacher came in. 老师进来时，学生们正在讲话。（点线重合）前一个动作是延续性的，而后一个动作时非延续性的二、while的意思是“在……同时（at the same time that )”“在……期间(for as long as, during the time that）”。从while的本身词义来看，它只能表示一段时间，不能表示具体的时间点。在时间上可以是“线线重合”或“点线重合”，但不能表示“点点重合”。例如： 1、He was watching TV while she was cooking. 她做饭时，他在看电视。（线线重合） 2、He was waiting for me while I was working. 我工作的时候，他正等着我。（线线重合） 3、He asked me a question while I was speaking. 我在讲话时，他问了我一个问题。（点线重合）

第七--when-while-as-区别及练习.

When while as区别一、根据从句动作的持续性来区分 1、“主短从长”型：即主句是一个短暂性动作，而从句是一个持续性动作，此时三者都可用。如： Jim hurt his arm while［when， as］ he was playing tennis. 吉姆打网球时把手臂扭伤了。 2、“主长从长”型：即主句和从句为两个同时进行的动作或存在的状态，且强调主句动作或状态延续到从句所指的整个时间，此时通常要用while。 I always listen to the radio while I’m driving. 我总是一边开车一边听收音机。 He didn’t ask me in; he kept me standing at the door while he read the message. 他没有让我进去，他只顾看那张条子，让我站在门口等着。但是，若主句和从句所表示的两个同时进行的动作含有“一边……一边”之意时，则习惯上要用as。如： He swung his arms as he walked. 他走路时摆动着手臂。 3、“主长从短”型：即主句是一个持续性动作，而从句是一个短暂性动作，此时可以用as 或when，但不能用while。如： It was raining hard when [as] we arrived. 我们到达时正下着大雨。二、根据主句与从句动作是否同时发生来区分 1、若主句与从句表示的是两个同时发生的短暂性动作，含有类似汉语“一……就”的意思，英语一般要用as (也可用when)。如： The ice cracked as [when] I stepped onto it. 我一踩冰就裂了。 2、若主句与从句表示的是两个几乎同时发生的短暂性动作，含有类似汉语“刚要……就”“正要……却”的意思，英语一般要用as(也可用when)，且此时通常连用副词just。如： I caught him just when [as] he was leaving the building. 他正要离开大楼的时候，我把他截住了。三、根据是否具有伴随变化来区分若要表示主句动作伴随从句动作同时发展变化，有类似汉语“随着”的意思，英语习惯上要用as，而不用when或while。如： The room grew colder as the fire burnt down. 随着炉火逐渐减弱，房间越来越冷。注：若不是引导从句，而是引出一个短语，则用with，不用as。如： With winter coming on, it’s time to buy warm clothes. 随着冬天到来，该买暖和衣裳了。四、根据从句动作的规律性来区分若暗示一种规律性，表示“每当……的时候”，英语一般要用when。如： It’s cold when it snows. 下雪时天冷。五、根据主从句动作的先后顺序来区分若主句与从句所表示的动作不是同时发生，而是有先后顺序时，一般要用when。

When while as的区别和用法(综合整理)

When while as的区别和用法 when的用法当主句使用持续性动词时. Dave was eating,when the doorbell rang.门铃响时,大卫在吃饭. 2.一个动作紧接着另一个动作发生. When the lights went out, I lit some candles.灯灭了,我赶紧点上一些蜡烛. 3.谈论生命中的某一阶段,或过去的某段时间. His mother called him Robbie when he was a baby. 在他很小时,他妈妈叫他Robbin. 4.指"每一次" When I turn on the TV, smoke comes out the back. 每当我打开电视,就有烟从后面冒出. while/as 的用法从句多为进行时,而且为持续性动词. I'll look after the children while you are making dinner. 你做饭,我来照顾孩子. 注意事项: (1) “主短从长”型：主句表示的是一个短暂性动作，从句表示的是一个持续性动作，三者都可用： He fell asleep when [while, as] he was reading. 他看书时睡着了。 Jim hurt his arm while［when，as］he was playing tennis. 吉姆打网球时把手臂扭伤了。 As［When，While］she was waiting for the train，she became very impatient. 她在等火车时，变得很不耐烦。 (2) “主长从长”型：若主、从句表示两个同时进行的持续性动作，且强调主句表示的动作延续到从句所指的整个时间，通常要用while： Don’t talk while you’re eating. 吃饭时不要说话。 I kept silent while he was writing. 在他写的时候，我默不做声。但是，若主从句表示的两个同时进行的动作含有“一边…一边”之意思，通常用as：

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二、设置工程默认的单位 1．选择下拉菜单中的Options > project options > Global Unit 设置为mm 2．修改其中的单位点击OK完成操作。三、创建一个schematic原理图 1．选择菜单Project > Add Schematic > New Schematic 2．输入原理图的文件名例如：filter 四、放置元器件 1．按一下左下窗口的Elem，出现元件对话框 2．按一下其中的Lumped Element旁边的“+”号，扩展Lumped Element组 3．选择其下面的Inductor子组，再选中下方窗口显示IND模型，用鼠标左键选中并按住拖到schematic 窗口的合适位置出，释放左键。如需改动元件位置再用左键选择拖动即可。 4．再重复上述操作，在schematic中放置一共四个IND电感。并使他们连起来位置如图1所示。 5．选择Capacitor子组，再选中下方窗口中的CAP模型，拖动至schematic中放置位置如图1与电感连接。在拖动过程中按住左键并单击右键可以旋转器件(为什么我旋转不了？因为要在第3步把元件从左边的窗口往后边的电路图中拖的过程中才能旋转)。五、连接导线鼠标移至C1的下端节点此时鼠标形状改变，点中并拖动连接C2、C3的下面节点，完成连线。六、在节点上放置端口 1．选择下拉菜单Schematic > Add Port； 2．移动鼠标到L1的左端放置端口1，并与L1连接； 3．重复上操作放置端口2连接L4的右端，见图1。七、放置接地点 1．选择下拉菜单Schematic > Add Ground； 2．鼠标移动放置到C1的下节点。八、编辑元件参数双击元器件对应的参数即可修改其参数，修改L1和L4为15nH, L2和L3为30nH, C1和C3为8pF, C2为10pF。九、确定仿真频率 1． Options > project options > Frequency Values 2．修改单位为MHz，输入100在Start field，1000在Stop field，输入10作为步长Step field。其余默认。单击Apply(一定要点击，否则设置无效！). 4．单击Ok完成仿真频率的设置十、创建图表 1．右键工程视图中的Graphs组，选择Add Graph 2．输入名字“s21 and s11”选择Rectangular单击Ok。

when,while,as引导时间状语从句的区别

when，while，as引导时间状语从句的区别 when，while，as显然都可以引导时间状语从句，但用法区别非常大。一、when可以和延续性动词连用，也可以和短暂性动词连用；而while和as只能和延续性动词连用。 ①Why do you want a new job when youve got such a good one already？（get 为短暂性动词）你已经找到如此好的工作，为何还想再找新的？ ②Sorry，I was out when you called me．（call为短暂性动词）对不起，你打电话时我刚好外出了。 ③Strike while the iron is hot．（is为延续性动词，表示一种持续的状态）趁热打铁。 ④The students took notes as they listened．（listen为延续性动词）学生们边听课边做笔记。二、when从句的谓语动词可以在主句谓语动作之前、之后或同时发生；while 和as从句的谓语动作必须是和主句谓语动作同时发生。 1．从句动作在主句动作前发生，只用when。 ①When he had finished his homework，he took a short rest．（finished先发生）当他完成作业后，他休息了一会儿。 ②When I got to the airport，the guests had left．（got to后发生）当我赶到飞机场时，客人们已经离开了。 2．从句动作和主句动作同时发生，且从句动作为延续性动词时，when，while，as都可使用。 ①When ／While ／As we were dancing，a stranger came in．（dance为延续性动词）当我们跳舞时，一位陌生人走了进来。 ②When ／While ／As she was making a phonecall，I was writing a letter．（make为延续性动词）当她在打电话时，我正在写信。 3．当主句、从句动作同时进行，从句动作的时间概念淡化，而主要表示主句动作发生的背景或条件时，只能用as。这时，as常表示“随着……”；“一边……，一边……”之意。 ①As the time went on，the weather got worse．（as表示“随着……”之意） ②The atmosphere gets thinner and thinner as the height increases．随着高度的增加，大气越来越稀薄。 ③As years go by，China is getting stronger and richer．随着时间一年一年过去，中国变得越来越富强了。 ④The little girls sang as they went．小姑娘们一边走，一边唱。 ⑤The sad mother sat on the roadside，shouting as she was crying．伤心的妈妈坐在路边，边哭边叫。 4．在将来时从句中，常用when，且从句须用一般时代替将来时。 ①You shall borrow the book when I have finished reading it．在我读完这本书后，你可以借阅。 ②When the manager comes here for a visit next week，Ill talk with him about this．下周，经理来这参观时，我会和他谈谈此事。三、when用于表示“一……就……”的句型中（指过去的事情）。 sb．had hardly（＝scarcely）done sth．when．．．＝Hardly ／Scarcely had sb．done sth．when．．．

When,While,As引导时间状语从句的区别

When，While，As引导时间状语从句的区别 when，while，as显然都可以引导时间状语从句，但用法区别非常大。一、when可以和延续性动词连用，也可以和短暂性动词连用；而while和as 只能和延续性动词连用。 ① Why do you want a new job when you’ve got such a good one already？（get为短暂性动词）你已经找到如此好的工作，为何还想再找新的？ ②Sorry，I was out when you called me．（call为短暂性动词）对不起，你打电话时我刚好外出了。 ③Strike while the iron is hot．（is为延续性动词，表示一种持续的状态）趁热打铁。 ④ The students took notes as they listened．（listen为延续性动词）学生们边听课边做笔记。二、when从句的谓语动词可以在主句谓语动作之前、之后或同时发生；while 和as从句的谓语动作必须是和主句谓语动作同时发生。 1．从句动作在主句动作前发生，只用 when。 ①When he had finished his homework，he took a short rest．（finished 先发生）当他完成作业后，他休息了一会儿。 ②When I got to the airport，the guests had left．（got to后发生）当我赶到飞机场时，客人们已经离开了。 2．从句动作和主句动作同时发生，且从句动作为延续性动词时，when，while，as都可使用。 ①When ／While ／As we were dancing，a stranger came in．（dance为延续性动词）当我们跳舞时，一位陌生人走了进来。 ②When ／While ／As she was making a phone call，I was writing a letter．（make为延续性动词）当她在打电话时，我正在写信。 3．当主句、从句动作同时进行，从句动作的时间概念淡化，而主要表示主句动作发生的背景或条件时，只能用 as。这时，as常表示“随着……”；“一边……，一边……”之意。 ① As the time went on，the weather got worse．（as表示“随着……”之意） ② The atmosphere gets thinner and thinner as the height increases．随着高度的增加，大气越来越稀薄。 ③As years go by，China is getting stronger and richer．随着时间一年一年过去，中国变得越来越富强了。 ④The little girls sang as they went．小姑娘们一边走，一边唱。 ⑤The sad mother sat on the roadside，shouting as she was crying．伤心的妈妈坐在路边，边哭边叫。 4．在将来时从句中，常用when，且从句须用一般时代替将来时。 ①You shall borrow the book when I have finished reading it．在我读完这本书后，你可以借阅。 ②When the manager comes here for a visit next week，Ill talk with him about this．下周，经理来这参观时，我会和他谈谈此事。三、when用于表示“一……就……”的句型中（指过去的事情）。

When, while, as的区别和用法

When, while, as的区别和用法版本一 (1) 若主句表示的是一个短暂性动作，从句表示的是一个持续性动作，三者都可用： He fell asleep when [while, as] he was reading. 他看书时睡着了。【注】as 用于引出一个持续性动词表示“在……期间”时，其谓语通常只能是那些含有动作(action)和发展(development) 意味的动词，一般不能是那些不用于进行时态的动词(如be, seem, love, want, agree, see, know, have 等)，所以下面一句中的while 不能换为as： A：I’m going to the post office. 我要去邮局。 B：While you’re there, can you get me some stamps? 当你在邮局时，能帮我买几张邮票吗? (2) 若主、从句表示两个同时进行的持续性动作，且强调主句表示的动作延续到从句所指的整个时间，通常要用while： Don’t talk while you’re eating. 吃饭时不要说话。 I kept silent while he was writing. 在他写的时候，我默不做声。但是，若主从句表示的两个同时进行的动作含有“一边…一边”之意思，通常用as： She sang as she went along. 她边走边唱。 (3) 若从句是一个短暂性动作，主句是一个持续性动作，可用as / when 但不用while： It was raining hard when [as] we arrived. 我们到达时正下着大雨。 (4) 若主从句表示的是两个同时(或几乎同时)发生的短暂性动作，用as / when： I thought of it just when [as] you opened your mouth. 就在你要说的时候，我也想到了。 (5) 若要表示两个正在发展变化的情况，相当于汉语的“随着”，一般用as： Things are getting better and better as time goes on. 随着时间的推移，情况越来越好。 As it grew darker, it became colder. 天色越晚，天气越冷。 (6) 表示“每当…的时候”(暗示一种规律性)，一般要用when： It’s cold when it snows. 下雪时天冷。 He smiles when you praise him. 你夸奖他时他总是笑笑。 (7) 若主从句所表示的动作不是同时发生，而是有先后顺序时，一般要用when： I will go home when he comes back. 他回来时，我就回家去。 (8) when 可用作并列连词，表示“这时(突然)”；while 也可以用作并列连词，表示“而”、“却”(表示对比)；但as 则没有类似用法： We were about to start when it began to rain. 我们正要出发，这时天开始下雨了。 He likes coffee, while she likes tea. 他喜欢咖啡，而她却喜欢茶。 (9) as 和when 后均可直接跟一个名词，构成省略句，但while 一般不这样用： As [When] a boy, he lived in Japan. 他小时候在日本。

第七whenwhileas区别及练习

When while as 区别一、根据从句动作的持续性来区分 1、“主短从长”型：即主句是一个短暂性动作，而从句是一个持续性动作，此时三者都可用。如： Jim hurt his arm while ［ when， as］ he was playing tennis. 吉姆打网球时把手臂扭伤了。 2、“主长从长”型：即主句和从句为两个同时进行的动作或存在的状态，状态延续到从句所指的整个时间，此时通常要用while 。且强调主句动作或 I always listen to the radio while I ’ m driving. 我总是一边开车一边听收音机。 He didn ’ t ask me in; he kept me standing at the door while he read the message. 他没有让我进去，他只顾看那张条子，让我站在门口等着。但是，若主句和从句所表示的两个同时进行的动作含有“一边,, 一边”之意时，则习惯上要用 as。如： He swung his arms as he walked. 他走路时摆动着手臂。 3、“主长从短”型：即主句是一个持续性动作，而从句是一个短暂性动作，此时可以用as 或when，但不能用 while 。如： It was raining hard when [as] we arrived.我们到达时正下着大雨。二、根据主句与从句动作是否同时发生来区分 1、若主句与从句表示的是两个同时发生的短暂性动作，含有类似汉语 “一英语一般要用 as (也可用 when)。如： ,, 就的”意思，The ice cracked as [when] I stepped onto it. 我一踩冰就裂了。 2、若主句与从句表示的是两个几乎同时发生的短暂性动作，含有类似汉语“刚要“正要 ,, 却”的意思，英语一般要用 as(也可用 when)，且此时通常连用副词 ,, just。如：就” I caught him just when [as] he was leaving the building. 他正要离开大楼的时候，我把他截住了。三、根据是否具有伴随变化来区分若要表示主句动作伴随从句动作同时发展变化，有类似汉语“随着”的意思，英语习惯上要用as，而不用 when 或 while 。如： The room grew colder as the fire burnt down.随着炉火逐渐减弱，房间越来越冷。注：若不是引导从句，而是引出一个短语，则用with ，不用 as。如： With winter coming on, it ’ s time to buy warm clothes. 随着冬天到来，该买暖和衣裳了。四、根据从句动作的规律性来区分若暗示一种规律性，表示“每当,, 的时候”，英语一般要用when 。如：It ’s cold when it snows. 下雪时天冷。五、根据主从句动作的先后顺序来区分若主句与从句所表示的动作不是同时发生，而是有先后顺序时，一般要用when 。

when while as区别用法详解

when/while/as区别用法详解 when, while, as都可作"当……的时候"解，但它们之间也有差别。若主句表示的是一个短暂性动作，从句表示的是一个持续性动作，三者都可用。 He fell asleep when/while/as he was reading. 他看书时睡着了。 when只表示一般的时间关系，它既可指时间的一点，也可指一段时间。用when时，从句的动作可与主句的动作同时发生，也可先于主句的动作，因此when用得最多。如： He was playing basketball when I saw him. 当我看见他的时候，他正在打篮球。 Don't forget to return this book for me, when you go to the library. 你去图书馆时，不要忘记替我还这本书。 while只能指一段时间，而不能指时间的一点。用while时，从句的动作或者与主句的动作同时发生，或者主句的动作是在从句的动作的进展过程中发生的。因此，从句中的谓语必须是表示延续性动作或状态的动词。这是while与when的主要差别。如： When we arrived in Beijing, it was raining. (arrive不是延续性的动词)我们到达北京时，天正在下雨。 Please do not trouble me while I am writing my homework. 我写作业时请不要打扰我。在用when和while连接的从句中，常省略与主句相同的主语和相应的be，而在as连接的从句中一般则不省略。如： He fell asleep while(he was)studying his grammar book.他在阅读语法书的时候睡着了。While in London,he studied music.他在伦敦的时候，研究音乐。 when 可用作并列连词，表示“这时(突然)”；while 也可以用作并列连词，表示“而”、“却”(表示对比)；但as 则没有类似用法： We were about to start when it began to rain. 我们正要出发，这时天开始下雨了。 He likes coffee, while she likes tea. 他喜欢咖啡，而她却喜欢茶。

when,while和as引导时间状语从句的用法

when, while 和 as 引导时间状语从句的用法这三个词的意思很简单，都有“当……时候”的意思。但学生经常会问三个词的区别在哪儿，特别是在做选择题的时候。别说是学生，就我个人而言，做这样的选择题要保证百分之百的正确也是不可能的。现根据大量的实例和个人的思考，做一点小结，供大家参考。一、when 的用法如果只从现象来看，when 从句用的最多的是一般过去时，而主句的时态没有限制，根据具体情况而定。 When he was a child he was always trying out new ideas. 他小时候就常常试验一些新的设想。 when she came into my room I was just reading a book. 她走进我房间时，我正在看书。 Were you writing when the teacher came in? 老师进来的时候，你在写信吗？ Sorry，I was out when you called me. 对不起，你打电话来的时候我出去了。 He was on the point of leaving when someone knocked at the door. 他正要走,这时有人敲门。 I thought of it just when you opened your mouth. 就在你要说话的时候,我也想到了。 I had hardly[scarcely] closed my eyes when someone knocked at the door. 我刚一闭上眼，就有人在敲门了。根据以上的例句，我们可以总结出一点：when 从句的A事件，相当于另一个事件B发生的时间点。也就是说，when 从句的重点不在动作本身发生的状态，而只是把它作为一个时间点，所以when 多数情况下用的是一般过去时，则不用正在进行时。因为如果用正在进行时，它表示的就是一段时间而不是一个时间点了。根据这一点，有的文章补充说：when 从句的动词大多是瞬时动词。这种说法也可以参照。实际上，when 从句也可以有其它的时态，但几乎也不用进行时，因为它也只是作为一个时间参照点。例如： When I got to the airport，the guests had left. 当我赶到飞机场时，客人们已经离开了。 When he had finished his homework，he took a short rest．当他完成作业后，他休息了一会儿。 Why do you want a new job when you have got such a good one already？你已经找到如此好的工作，为何还想再找新的？ You shall borrow the book when I have finished reading it.

状语从句中的when,while ,as用法汇总

状语从句中的when, while和as的用法一．when，while，as在时间状语从句中的区别： ①三者均可表示“当……的时候”，如果主句表示的是短暂的动作，而从句表示的是一段时间，三者可通用。如： I met Kang Li as／when／while I was walking along the street．当我沿街散步时碰见了康丽。 ②when可以和延续性动词连用，也可以和短暂性动词连用；而while和as只能和延续性动词连用。如： It was snowing when we got to the airport．当我们到达机场时，天正下着雪。（不能用while） ③as强调主句与从句表示的动作同时发生，as常表示“随着……”；“一边……，一边……；while强调主句表示的动作持续于while所指的整个时间内；when 可指主、从句所述动作同时或先后发生。如： As the time went on，the weather got worse．（as表示“随着……”之意） He sang as he went along．他边走边唱。 Please write while I read．我读的时候，请写下来。 When he reached home，he had a little rest．回到家后，他休息了一会儿。 ④when用于表示“一……就……”的句型中（指过去的事情）。 somebody had hardly（＝scarcely）done …when．．．＝Hardly ／Scarcely had somebody done …when．．． ①I had hardly ／scarcely closed my eyes when someone knocked at the door．＝Hardly ／Scarcely had I closed my eyes when someone knocked at the door．我刚一闭上眼，就有人在敲门了。二.when, while和as都可引导让步状语从句： ①when引导让步状语从句，意为“尽管，虽然”相当于though或although: They stopped trying when they might have succeeded next time. ②while引导让步状语从句，相当于although ，是较为正式的书面语: While I am willing to go, I would like it better that you went. ③as引导让步状语从句必须倒装，从句中的表语，状语或动词原形置于句首，若表语为名词，前置时省略冠词。 Child as he is, he knows a lot. Much as I like it, I will not buy it, for it’s too expensive.

AWR_Microwave_Office设计套件的介绍

AWR_Microwave_Office设计套件的介绍随着电磁场和微波电路领域数值计算方法的发展，在最近几年出现了大量的电磁场和微波电路仿真软件。在这些软件中，多数软件都属于准3维或称为维电磁仿真软件。例如，Agilent公司的ADS（Advanced Design System）、AWR公司的Microwave Office、Ansoft 公司的Esemble、Serenade和CST公司的CST Design Studio等。目前，真正意义上的三维电磁场仿真软件只有Ansoft公司的HFSS、CST公司的Mafia、CST Microwave Studio、Zeland 公司的Fidelity和IMST GmbH公司的EMPIRE。从理论上讲，这些软件都能仿真任意三维结构的电磁性能。其中，HFSS （HFSS是英文高频结构仿真器（High Frequency Structure Simulator）的缩写）是一种最早出现在商业市场的电磁场三维仿真软件。因此，这一软件在全世界有比较大的用户群体。由于HFSS进入中国市场较早，所以目前国内的电磁场仿真方面HFSS的使用者众多，特别是在各大通信技术研究单位、公司、高校非常普及。

AWR_Microwave_Office设计套件是专门的微波/射频软件，Microwave Office软件是通过两个模拟器来对微波平面电路进行模拟和仿真的。对于由集总元件构成的电路, 用电路的方法来处理较为简便。该软件设有一个叫“VoltaireXL”的模拟器来处理集总元件构成的微波平面电路问题。而对于由具体的微带几何图形构成的分布参数微波平面电路则采用场的方法较为有效, 该软件采用的是一个叫“EMSight”的模拟器来处理任何多层平面结构的三维电磁场的问题。由于这里意在着重于电磁场分析，所以仅涉及“EMSight”模拟器。下面是它的具体功能：“EMSight”模拟器是一个完整的三维电磁场模拟程序包, 它可用于平面高频电路和天线结构的分析。模拟器分析的电路都安装在一个矩形的金属包装盒内, 对于电路的层数和端口

微波冶金综述 2015年：Microwave-assisted metallurgy

Microwave-assisted metallurgy Zhiwei Peng1,2and Jiann-Yang Hwang*2,3 Microwave heating has been extensively explored in various fields of materials processing.This technology exhibits unique characteristics including volumetric and selective heating,which eventually lead to many exceptional advantages over conventional processing methods including both energy and cost savings,improved product quality,faster processing and greater eco-friendliness,making microwave heating appropriate for applications in metallurgy.This paper presents a critical review on the use of microwave energy in metallurgy,with emphasis on both fundamentals of microwave heating and recent experimental efforts on extractive metallurgy via pyrometallurgical and/or hydrometallurgical routes.Applications to metallurgical processes for extraction of various metals,including heavy metals(Fe,Ni,Co,Cu,Pb and Zn),light metals(Al and Mg),rare metals(Ti,Mo,W and Re)and precious metals(Au,Ag and Pt),are reviewed and discussed. Keywords:Microwave heating,Permittivity,Permeability,Pyrometallurgy,Hydrometallurgy,Materials pretreatment,Microwave reduction/leaching, Waste remediation Introduction Microwave heating has emerged as a unique and distin-guishing technology used for materials processing.1–4 The rapid advancement of this heating technology has inspired many more encouraging and successful applica-tions to metallurgy.The earliest application of micro-wave energy to metallurgy can be traced back to1960s when a patent for microwave treatment of iron ores was granted.5Around the same time,high-temperature microwave processing of oxide and sul?de minerals was reported.6Subsequent studies demonstrated strong microwave absorption in various metal-bearing minerals such as magnetite and pyrite.7Inspired by these dis-coveries,the direct reduction of metal oxides using microwave energy has been extensively explored since the early1990s.8–10It is largely documented that micro-wave reduction of many metal-bearing minerals could be achieved rapidly,which is attributed to the volumetric and selective heating characteristics of microwave heating. Consequently,there can be a considerable reduction in energy consumption and pollution(e.g.CO2and SO2 emissions)compared with conventional processes.11This cost saving,environmentally friendly feature is also accompanied by enhanced microwave heating character-istics(microwave absorption capabilities)of metal sources. Thus,microwave energy is?nding increasing applications in sub?elds of metallurgy,such as pretreatment of metal-bearing materials and metallurgical waste remediation.12 In many cases,the unique advantages of microwave heating were veri?ed by experimental observations. However,from studies over the past half century,it is recognised that there are still dif?culties that hinder the advancement of microwave-assisted metallurgy and more broad applications of the technology to materials proces-sing.Many challenges are confronted in the commercia-lisation and industrialisation of microwave-assisted metallurgy.13 As microwave energy is being used for the extraction of a variety of metals,this paper presents a critical and comprehensive review of the scienti?c literature on microwave-assisted metallurgy.The authors try to put emphasis on both the principles and applications of microwave heating associated with numerous metallurgi-cal processes for extraction of various metals including heavy metals(Fe,Ni,Co,Cu,Pb and Zn),light metals(Al and Mg),rare metals(Ti,Mo,W and Re)and precious metals(Au,Ag and Pt).Some key fundamentals of microwave heating that relate microwave–material inter-actions will be described by introducing the main microwave heating mechanisms,crucial physical para-meters(e.g.permittivity,permeability,microwave pene-tration depth,re?ection loss and impedance matching degree),and characteristics of microwave heating.This is followed by a brief introduction of features in microwave-assisted metallurgy and a detailed discussion on various applications to extractive metallurgy.Concluding remarks touch on major dif?culties that limit further development of microwave-assisted metallurgy followed by promising measures that address challenges faced with commercia-lisation and industrialisation. Microwave heating fundamentals Introduction to microwave heating Microwaves are electromagnetic waves with wavelengths from1mm to1m with corresponding frequencies 1School of Minerals Processing and Bioengineering,Central South University,Changsha,Hunan410083,China 2Department of Materials Science and Engineering,Michigan Technological University,Houghton,MI49931,USA 3Advanced Materials R&D Centre of WISCO,Beijing102211,China *Corresponding author,email jhwang@https://www.wendangku.net/doc/5c12282466.html, ?2015Institute of Materials,Minerals and Mining and ASM International Published by Maney for the Institute and ASM International Received13March2014;accepted8August2014 DOI10.1179/1743280414Y.0000000042International Materials Reviews2015VOL60NO1 30