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Thermochimica Acta 521 (2011) 80–83

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Thermochimica

Acta

j o u r n a l h o m e p a g e :w w w.e l s e v i e r.c o m /l o c a t e /t c

Subsolidus binary phase diagram of the perovskite type layer materials (n -C n H 2n +1NH 3)2ZnCl 4(n =10,12,14)

Weizhen Cui a ,b ,Kezhong Wu a ,?,Xiaodi Liu a ,Liuqing Wen a ,Biyan Ren a

a Department of Chemistry and Material Science,Hebei Normal University,113YuHua Rd.,Shijiazhuang 050016,China b

Department of Chemistry,Cangzhou Teachers College,Hebei,Cangzhou 061001,China

a r t i c l e

i n f o

Article history:

Received 22February 2011

Received in revised form 11April 2011Accepted 11April 2011

Available online 16 April 2011

Keywords:

Decylammonium tetrachlorozincate Dodecylammonium tetrachlorozincate Tetradecylammonium tetrachlorozincate Phase diagram

a b s t r a c t

The perovskite type layer materials (n -C n H 2n +1NH 3)2ZnCl 4(n =10,12,14)were studied and a series of their mixtures were prepared from their absolute ethanol solutions.The low temperature crystal structures of the pure salts are characteristic of the piling of sandwiches in which a two-dimensional macro-anion ZnCl 42?is sandwiched between two alkylammonium layers.These layers become conformationally dis-ordered in the high temperature phases.It results in the thermotropic solid–solid phase transitions in the (n -C n H 2n +1NH 3)2ZnCl 4.The subsolidus binary phase diagrams of (n -C 10H 21NH 3)2ZnCl 4–(n -C 14H 29NH 3)2ZnCl 4and (n -C 12H 25NH 3)2ZnCl 4–(n -C 14H 29NH 3)2ZnCl 4were established by differential thermal analysis (DTA)and X-ray diffraction (XRD).The existence of the intermediate compound and two eutectoid invariants were observed in each phase diagram.There are three noticeable solid solution ranges (?,?,?)at the left boundary,right boundary and middle of the phase diagram.

1.Introduction

The perovskite-type compounds of the general formula A 2BX 4or ABX 3(A,B is metal;X is halogen or oxygen)form a numer-ous class of materials that are important both for fundamental and technological research.Similar physical and structural prop-erties are observed when metal A is substituted by an [NR 4]+ion (R is H,alkyl,or aryl)[1–3].All the compounds show solid–solid order–disorder phase transitions below https://www.wendangku.net/doc/e511241815.html,yered organic–inorganic hybrid compounds have been widely studied,since they can,in principle,combine properties of the inorganic and organic parts within a single system.Many studies have been devoted to layered organic-based perovskite structures,whose properties can be tuned by varying the organic component and the perovskite matrix [4–6].We synthesized three types of materials of [NR 4]2ZnCl 4in bis(n -alkylammonium)tetrachlorozincate(II)with the general formula (n -C 10H 21NH 3)2ZnCl 4(short notation;C 10Zn),(n -C 12H 25NH 3)2ZnCl 4(C 12Zn)and (n -C 14H 29NH 3)2ZnCl 4(C 14Zn).The three compounds are known to crystallize in a bidimensional structure of perovskite [7,8].The bidimensional parallel sheets of corner-sharing ZnCl 42?tetrahedra are sandwiched between dou-ble layers of n -alkylammonium cations.The layers are bound by van der Waals forces between (CH 2)n CH 3groups and by long-range Coulomb forces.The –NH 3+groups of the chains occupy the cavities

?Corresponding author.Tel.:+86031186268049.E-mail address:wukzh688@https://www.wendangku.net/doc/e511241815.html, (K.Wu).

of the ZnCl 42?layers and are bonded by hydrogen bonds to the chlo-rine atoms.Applications of such materials include the development of functional magnetic,electronic,and optoelectronic materials.The physical properties and structures of C n Zn [3–10]have been previously researched.The binary phase diagrams for C 10Zn–C 12Zn [11],C 10Zn–C 16Zn [12,13],C 12Zn–C 16Zn [12,13],C 12Zn–C 18Zn [14]have been reported.Among them,Ruan and Li obtained a different result that C 10Zn–C 16Zn [12]shows absolute immiscibility.As we know,the binary phase diagrams of C 10Zn–C 14Zn and C 12Zn–C 14Zn have not been studied.In this work the subsolidus phase diagrams of C 10Zn–C 14Zn and C 12Zn–C 14Zn were established by differential thermal analysis (DTA)and X-ray diffraction (XRD).

2.Experimental procedure

ZnCl 2,concentrated HCl and absolute ethanol were analytical grade.Decylamine (A.P.),Dodecylamine (A.P.)and tetradecylamine (A.P.)were purchased from TOKYO KASEI KOGYO Co.Ltd.(Japan).

For the synthesis of C n Zn,the hot absolute ethanol solutions of ZnCl 2,concentrated HCl and the corresponding alkylamine were mixed in a 1:2:2molar ratio.The solutions were concentrated by boiling for 30min,then cooled to room temperature.After ?ltra-tion,the products were recrystallized twice from absolute ethanol.Finally,they were placed in a vacuum desiccator for 8h at about 353K.C 10Zn,C 12Zn and C 14Zn were analyzed with an MT-3CHN elemental analyzer (Japan).Elemental analyses calc.(%)for C 10Zn:C 45.86,H 9.24,N 5.35,Cl 27.15;Found:C 45.68,H 9.27,N 5.27,Cl 27.34.Anal.Calcd.For C 12Zn:C 49.71,H 9.73,N 4.83,Cl 24.45;

W.Cui et al./Thermochimica Acta521 (2011) 80–83

Fig.1.DTA curves of C10Zn–C14Zn with different W C

14Zn

Found:C49.44,H9.79,N4.69,Cl24.64.Anal.Calcd.For C14Zn:C 52.82,H10.06,N4.40,Cl22.36;Found:C53.00,H10.25,N4.34,Cl 22.19.The C n Zn were weighed exactly in the desired proportions to prepare the mixed samples of C10Zn–C14Zn and C12Zn–C14Zn. The two components were dissolved in absolute ethanol,then the solvent was evaporated.The samples were dried in a vacuum des-iccators for8h at a temperature of about353K.The concentrations

of all materials in the binary system were expressed as W C

14Zn %.

The DTA curve was measured on a CDR-4P differential scanning calorimeter(Shanghai Scale Instrument Plant)at a scanning rate of5K/min in a static atmosphere.Samples of about4.5mg were sealed in aluminum crucibles.X-ray diffraction patterns on com-pacted samples of the powders were taken with a D/MAX-RA X-ray diffractometer(made in Japan)using CuK?radiation(Ni?lter)at a scanning rate of2min?1.The voltage and electric current were 40kV and100mA,respectively.The subsolidus phase relations of the C10Zn–C14Zn and C12Zn–C14Zn systems were investigated in air.

3.Results and discussion

3.1.Thermal analysis

The C10Zn–C14Zn binary systems were examined in the entire composition range and in a temperature range of298–380K. Fig.1shows some typical DTA curves of C10Zn–C14Zn binary sys-

tems with different W C

14Zn %.The results of the DTA experiments

obtained using the“Shape factors method”[15]are listed in Table1. All the C10Zn–C14Zn binary systems show solid–solid phase tran-sitions in the temperature range330–370K.The data in Table1 show that the value of the transition temperature decreases with

increasing W C

14Zn %in the range from0to31.53%.Then,the phase

transition temperature?rst rises from W C

14Zn %31.53to60.04%.The

?rst eutectoid temperature at about338K appears in the W C

14Zn %

range9.06–51.05%.The phase transition temperature decreases

again from W C

14Zn %60.04to76.53%,and then rises with the increas-

ing W C

14Zn %.The second eutectoid temperature at about335K was

found in the W C

14Zn %range of66.03–84.93%.Table1reveals that the

?rst eutectoid temperature is not close to that pure C10Zn,nor does the second eutectoid temperature end near that of pure C14Zn.The range of the?rst eutectoid temperature does not end close to the beginning of the second eutectoid temperature.It is clear that the phase transition temperatures of the binary system C10Zn–C14Zn Table1

Solid–solid transition temperatures for the C10Zn–C14Zn binary systems with dif-ferent W C

14Zn

W C

14Zn

%T e

a(K)T e

(K)T s

b(K)T s

(K) 0(C10Zn)354

2.19347353

5.03342352

9.06338351

13.00337350

14.73338349 20.07338349 22.97339347 24.86338346 29.03338344 31.99339341 35.00338343 40.00338347 45.03339352 48.00337353 51.05338357

53.00341359

54.96346359 56.94349360 60.04357362 63.01340360 66.03335358 69.00335353 72.93334349 74.96336345 79.91335352 84.93336358 89.88345364 94.00351367 98.10364369

100(C14Zn)369

a T e eutectoid invariant.

b T s solid–solid transition temperature.

in solid–solid phase transitions show a strong dependence on W C

14Zn

%.The reason is that there are not only intermediates of the form(n-C10H21NH3)2/5(n-C14H29NH3)3/5ZnCl4(short notation; C10C14Zn)but also three solid solution ranges existing at the left boundary,right boundary and middle of the phase diagram of C10Zn–C14Zn.

3.2.X-ray diffraction

Fig.2shows the XRD diffraction results.Table2summarizes the d values of strong peaks with bigger relative intensity at room temperature for pure C10Zn,C14Zn and their binary systems.It is ?nd that d values of sample from W C

14Zn

%5.03%is similar to that of pure C10Zn,indicating a single-phase region.In this concentration range from pure C10Zn W C

14Zn

%=0to9.06%,C10C14Zn dissolves in C10Zn to form a solid solution?.Similarly,samples with W C

14Zn

% from84.93%to pure C14Zn W C

14Zn

%=100%have homologous pat-terns,revealing that the C10C14Zn dissolves in C14Zn to form a solid solution?.In the same way,C10Zn–C14Zn samples with W C

14Zn

% from51.05%to66.03%have similar diffraction patterns,showing that C10Zn or C14Zn dissolved in C10C14Zn forms a single-phase ?.C10Zn–C14Zn samples with W C

14Zn

%from9.06to51.05%are in the two-phase region,and their patterns are an overlap of?and ?.The X-ray diffraction patterns of C10Zn–C14Zn samples with the W C

14Zn

%range of66.03–84.93%are an overlap of?and?and thus in the two-phase region.

3.3.Establishment of phase diagram

The subsolidus binary phase diagram of C10Zn–C14Zn(Fig.3) was constructed according to the temperature-composition rela-tions from the DTA and X-ray diffraction experiments.The

82W.Cui et al./Thermochimica Acta 521 (2011) 80–83

Table 2

d values for C 10Zn C 14Zn,and their binary systems with different W C 14Zn %at room temperature.

C 10Zn (nm)

5.03%

22.97%

48.00%

53.00%

63.01%

72.93%

84.93%

94.00%

C 14Zn

6.11432 6.18459 6.09744

7.778327.791797.739097.712647.817267.711047.734015.86709 5.92140 5.86098 6.15521 6.16969 6.13953 5.85455 5.90201 5.82904 5.847765.14262 5.19520 5.14039 5.89102 5.90031 5.87406 5.04335 5.08545 5.16983 5.188364.89315 4.93181 4.88914 5.19492 5.20179 5.17386 4.91227 4.95055 4.92005 4.927984.79583 4.83353 4.44864 4.93674 4.93809 4.92186 4.78955 4.81608 4.78629 4.799084.44612 4.48601 4.15651 4.81482 4.81623 4.79976 4.63243 4.65763 4.24591 4.252284.11054 4.13894 4.10654 4.65007 4.65242 4.63432 4.24159 4.26889 4.10423 4.112843.63082 3.65249 3.62780 4.25691 4.26059 4.24813 4.15256 4.12790 3.62959 3.636343.38251 3.40058 3.37915 4.12594 4.12856 4.11448 3.62966 3.64494 3.36454 3.371402.65671

2.66740

3.08559

3.64306 3.64418 3.63680 3.37658 3.38930 2.94094

2.94717

3.39228

3.39199 3.38259 2.94488

2.96035

2.96307

2.94706

subsolidus curve in Fig.3indicates that the maximum temperature of 362K at an equimass ratio of (n -C 10H 21NH 3)ZnCl 4to (n -C 14H 29NH 3)ZnCl 4(39.73%C 10Zn,60.27%C 14Zn).This composition corresponds to the stoichiometry of an intermediate compound (n -C 10H 21NH 3)(n -C 14H 29NH 3)ZnCl 4which is formed between two eutectoid invariants [16,17].The low temperature perovskite-layer structure of C 10Zn,C 14Zn and their binary system are organized by neutralizing ZnCl 42?with alkylammonium ions.Alkylammonium chains lie parallel to each other and are slightly tilted with respect to the normal of the inorganic layers.The adjacent alkyl chains interact with each other by van der Waals interactions,and are hydrogen bonded to ZnCl 42?.When the temperature is

increased

Fig.2.The diffraction patterns for C 10Zn,C 14Zn and their binary systems with dif-ferent W C 14Zn %.

320

330340350360

370380T / K

W C14Zn %

Fig.3.Phase diagram of the C 10Zn–C 14Zn system.

to 338K,the ?rst eutectoid invariant occurs from W C 14Zn %9.06to 51.05%.C 10Zn and C 10C 14Zn undergo a reversible solid–solid phase transformation.In this situation,the chains possess a large degree of motional freedom and a disordered phase appears.At the same time,the hydrogen bonds are weakened and even destroyed.The second eutectoid invariant appears from W C 14Zn %66.03%to 84.93%at 335K.Similarly,C 14Zn and C 10C 14Zn undergo a reversible solid–solid phase transformation.

The subsolidus binary phase diagram of C 12Zn–C 14Zn was obtained in the same way (see Fig.4).

The ?rst eutectoid temper-ature 341K appears in the W C 14Zn %range from 29.40to 55.77%.

320

330340350360

370380T / K

W C14Zn %

Fig.4.Phase diagram of the C 12Zn–C 14Zn system.

W.Cui et al./Thermochimica Acta521 (2011) 80–8383 The second eutectoid temperature at about338K was found in

the W C

14Zn %range from79.29to87.33%.The subsolidus curve

in Fig.4indicates that the maximum temperature of357K at an equimass ratio of(n-C12H25NH3)ZnCl4to(n-C14H29NH3)3ZnCl4 (39.73%C12Zn,60.27%C14Zn).This composition corresponds to the stoichiometry of an intermediate compound(n-C10H21NH3) (n-C14H29NH3)ZnCl4(C12C14Zn)which is formed between two eutectoid invariants.There are three noticeable solid solution ranges(?,?,?)at the left boundary,right boundary and middle of the phase diagram.

The phase diagrams of C10Zn–C14Zn and C12Zn–C14Zn obtained in this work are similar to that of C10Zn–C12Zn which has been reported in our previous work[11].For the intermediate com-pound of C10Zn–C12Zn systems,the mass ratio between the two n-alkylammonium groups is1:1.It is2:3for the interme-diate compound(n-C10H21NH3)2/5(n-C14H29NH3)3/5ZnCl4of the C10Zn–C14Zn binary system,and1:2for the intermediate com-pound(n-C12H25NH3)1/3(n-C14H29NH3)2/3ZnCl4(C12C14Zn)of the C12Zn–C14Zn binary system.Moreover the phase diagrams of C10Zn–C14Zn and C12Zn–C14Zn obtained in this work are different from those of the other homologous systems of C10Zn–C16Zn[12]. Partial miscibility was observed for the binary systems in this work, while the latter two binary systems show absolute immiscibility. This can be attributed to the difference in the molecular structure and size of the two compounds in the binary system,i.e.,the degree of the miscibility can be improved by reducing the differences in molecular structure and size.

4.Conclusion

The subsolidus binary phase diagrams of C10Zn–C14Zn and C12Zn–C14Zn mixtures were established by DTA and XRD in the temperature interval320K–370K.The two eutectoids occur in the

C10Zn–C14Zn system:e1at338±1K for W C

14Zn %=31.41%and e2

at335±1K for W C

14Zn %=76.37%,other two eutectoid occur in the

C12Zn–C14Zn system:e1at341±1K for W C

14Zn %=41.53%and e2

at339±1K for W C

14Zn %=84.07%.Their phase diagrams are very

similar,belonging to a partially miscible system.Intermediate com-pounds of(n-C10H21NH3)2/5(n-C14H29NH3)3/5ZnCl4(C10C14Zn) and(n-C12H25NH3)1/3(n-C14H29NH3)2/3ZnCl4(C12C14Zn)were observed in C10Zn–C14Zn and C12Zn–C14Zn system,respectively. There are three noticeable solid solution ranges,at the left bound-ary,right boundary,and middle of the phase diagram.It is revealed that the crystal structure and the size of the molecule are the essen-tial factors that affect the miscibility of the binary systems.Acknowledgements

This project was?nancially supported by National Natural Science Foundation of China(No.21073052),Natural Science Foundation of Hebei Province(No.E2009000307),Education Department Scienti?c Research Fund from Hebei Province(No. 2008469)and Science Foundation of Hebei Normal University (L2008Z07).

References

[1]M.Amami, A.Ben Salah,Comparative study of structural stability in

[NH4?n(CH3)n]2HgCl4and in related compounds,Cent.Eur.J.Chem.2(2004) 388–401.

[2]M.Seiler,Hyperbranched polymers:phase behavior and new applications in

the?eld of chemical engineering,Fluid Phase Equilib.241(2006)155–174. [3]K.Z.Wu,W.Z.Cui,J.J.Zhang,Subsolidus binary phase diagram of C12Mn/C16Mn

in thermotropic phase transitions materials,Thermochim.Acta463(2007) 15–17.

[4]M.Szafranski,K.Stahl,Crystal structure and phase transitions in perovskite-like

C(NH2)3SnCl3,J.Solid State Chem.180(2007)2209–2215.

[5]Y.Tabuchi,K.Asai,M.Rikukawa,Preparation and characterization of natural

lower dimensional layered perovskite-type compounds,J.Phys.Chem.Solids 61(2000)837–845.

[6]R.Jakubas,G.Bator,M.Gosniowska,Z.Clunik,J.Baran,J.Lefebver,Crystal struc-

ture and phase transition of[(CH3)2NH2]GaCl4,J.Phys.Chem.Solids58(1997) 989–998.

[7]K.Z.Wu,J.L.Li,J.J.Zhang,X.D.Liu,Nonisothermal kinetics of the solid–solid

phase transitions in the perovskite type layer compounds(C n H2n+1NH3)2ZnCl4, Chin.J.Chem.26(2008)216–219.

[8]K.W.Lee,C.E.Lee,Magnetic resonance study of the two-dimensional spin dif-

fusion in the Heisenberg paramaget(C18H37NH3)2MnCl4,Solid State Commun.

126(2003)343–346.

[9]K.Z.Wu,J.J.Zhang,X.D.Liu,Subsolidus phase diagram of binary system of ther-

motropic phase transitions compounds(n-C n H2n+1NH3)2MnCl4(n=12,14,16), Thermochim.Acta483(2009)55–57.

[10]K.K.Rangan,M.G.Kanatzidis,Mesolamellar thiogermanates

[C n H2n+1NH3]4Ge4S10,Inorg.Chim.Acta357(2004)4036–4044.

[11]K.Z.Wu,P.Zuo,X.D.Liu,Y.J.Li,Subsolidus binary phase diagram of C10Zn/C12Zn,

Thermochim.Acta397(2003)49–53.

[12]D.S.Ruan,W.P.Li,L.F.He,Q.H.Hu,Phase diagrams of binary system of alkyi-

ammonium tetrachlorometallates(II),J.Therm.Anal.45(1995)235–242. [13]K.Z.Wu,C.X.Zhang,Y.J.Li,X.D.Liu,Subsolidus binary phase diagrams of

C10ZnCl–C16ZnCl and C12ZnCl–C16ZnCl,J.Chin.Chem.Soc.52(2005)45–50. [14]K.Z.Wu,X.D.Wang,X.D.Liu,Phase diagram of binary system C12Zn–C18Zn,J.

Univ.Sci.Technol.Beijing10(2003)75–77.

[15]R.Courchinoux,N.B.Chanh,Y.Haget,Use of the“shape factors”as an empirical

method to determine the actual characteristic temperatures of binary phase diagrams by differential scanning calorimetry,Thermochim.Acta128(1988) 45–53.

[16]J.-I.Kim,S.J.Park,S.B.Kim,SLE and LLE for tri-butylphosphate or tri-octylamine

contained systems;extractive solvents of Molybdenum,Fluid Phase Equilib.

295(2010)172–176.

[17]U.Domanˇ?ska, A.Pobudkowska,P.Gierycz,Experimental solid–liquid

phase equiibria of{cholesterol+binary solvent mixture:1-alcohol (C4–C10)+cyclohexane},Fluid Phase Equilib.289(2010)20–31.