ISSN 0036�0236, Russian Journal of Inorganic Chemistry, 2010, Vol. 55, No. 8, pp. 1287–1291. © Pleiades Publishing, Ltd., 2010.Original Russian Text © T.V. Gubanova, E.I. Frolov, G.A. Filippova, I.K. Garkushin, 2010, published in Zhurnal Neorganicheskoi Khimii, 2010, Vol. 55, No. 8, pp. 1364–1369.

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Fused electrolytes for chemical current sourcesand fuel cells are now a promising line of appliedresearch in phase diagrams. Widely used are systemscontaining alkali metal halides, not only having valu�able properties, such as high enthalpies of melting andelectrical conductivity, but being also suitable for useas solvents for inorganic compounds that cannot beused as such [1].

METHODS AND REAGENTS

The title four�component system was studied bydifferential thermal analysis (DTA). A Pt–Pt/Rh(10% Rh) thermocouple served as a temperature gage;a KSP�4 automated potentiometer was used as arecorder. Freshly calcined Al2O3 served as a reference.Cooling rates were 12–15 K/min. The title system wasstudied at temperatures in the range from 350 to900°С. All compositions are expressed in molar per�

cent; temperature in degrees Celsius. The DTA sam�ple size was 0.2 g.

The starting reagents of high purity grade (Li2SO4),chemically pure grade (LiBr), or pure for analysisgrade (LiF) were calcined or fused (LiBr) before use.Lithium metavanadate was prepared as described in[2]. The purity of the reagents was monitored by pow�der X�ray diffraction (DRON�3 diffractometer, Ni�filtered CuK

α radiation).

EXPERIMENTAL

Experimental design for the LiF||F,Br, VO3, SO4system was performed subject to projective thermalanalysis rules [3]. Data on phase transitions in the rel�evant individual compounds were taken from [4]. Alltwo� and three�component boundary systems of theLiF–LiBr–Li2SO4–Li2MoO4 four�component system

LiF–LiBr–LiVO3–Li2SO4 Four�Component SystemT. V. Gubanova, E. I. Frolov, G. A. Filippova, and I. K. Garkushin

Samara State Technical University, Samara, RussiaReceived May 11, 2009

Abstract—Phase equilibria in theLiF–LiBr–LiVO3–Li2SO4 four�component system were studied using dif�ferential thermal analysis (DTA). The eutectic composition (mol %) was determined as LiF, 20.0; LiBr, 45.7;LiVO3, 25.7; Li2SO4, 8.6 with a melting temperature of 403°C and a specific enthalpy of melting of 216 kJ/kg.

DOI: 10.1134/S0036023610080243

PHYSICOCHEMICAL ANALYSIS OF INORGANIC SYSTEMS

Characteristics of eutectic and peritectic compositions in the two� and three�component subsystems of the LiF–LiBr–LiVO3–Li2SO4 system

System PointComponent concentrations, mol %

Tm, °CLiF LiBr LiVO3 Li2SO4

LiF–LiBr [5] Eutectic 23.0 77.0 467LiF–LiVO3 [6] The same 23.0 77.0 573LiF–Li2SO4 [6] '' 41.0 59.0 530

Peritectic 26.0 74.0 575LiBr–LiVO3 [7] Eutectic 57.0 43.0 473LiBr–Li2SO4 [8] The same 75.0 25.0 480

Peritectic 30.5 69.5 575LiVO3–Li2SO4 [9] Eutectic 87.0 13.0 591LiF–LiBr–LiVO3 [10] The same 16.8 52.0 31.2 428LiF–LiBr–Li2SO4 [11] '' 21.45 61.0 17.55 423LiF–LiVO3–Li2SO4 [2] '' 38.0 44.0 18.0 497

Peritectic 3.5 13.5 83.0 575LiBr–LiVO3–Li2SO4 [10] Eutectic 52.0 38.0 10.0 444

Peritectic 5.5 82.5 12.0 575LiF–LiBr–LiVO3–Li2SO4 Eutectic 20.0 45.7 25.7 8.6 403

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GUBANOVA et al.

have been studied earlier [5–11]. We revised the melt�ing temperatures and compositions of the alloys corre�sponding to invariant points in the two�componentsubsystems (table). The data on the two� and three�component systems are indicated in the developmentof the boundary elements of the title four�componentsystem (Figs. 1, 2).

Proceeding from the arrangement of the invariantpoints in low�dimension systems, we chose a two�dimensional vertical section in the lithium fluoridecrystallization volume, namely, a = [60.0% LiBr +40.0% LiF], b = [60.0 % Li2SO4 + 40.0 % LiF], and c =[60.0 % LiVO3 + 40.0 % LiF] (Figs. 2, 3). Then, in thissection, we chose to study one�dimensional verticalsection CD, where C = 48.0% LiBr + 40.0% LiF +12.0% Li2SO4 and D = 48.0% LiBr + 40.0% LiF +12.0% LiVO3 (Figs. 3, 4).

The T–x diagram of section CD was used to deter�

mine , the projection of the quaternary eutecticpoint; then, the composition of the projection wasused to calculate the concentration ratio of the lithium

E �

sulfate and lithium metavanadate components in the

quaternary eutectic. Consecutively studying

section (Figs. 3, 5) and section (Fig. 6), wedetermined the fixed component ratio LiBr : LiVO3 :Li2SO4 in the quaternary eutectic in section abc andthe composition corresponding to the quaternaryinvariant point, as follows: 20.0% LiF, 45.7% LiBr,25.7% LiVO3, and 8.6% Li2SO4. The eutectic phasereaction is L LiF + LiBr + LiVO3 + β�Li2SO4.

The polyhedron of the LiF–LiBr–LiVO3–Li2SO4system comprises the crystallization volumes of lith�ium fluoride, lithium bromide, lithium metavanadate,and α� (high�temperature) and β� (low�temperature)lithium sulfate phases (Fig. 1).

The specific enthalpy of melting of the eutecticalloy was 216 kJ/kg as derived by comparison with theenthalpy of melting of a reference (K2Cr2O7, Tm =397°C, 125.2 kJ/kg) as described in [12] and theresults of three measurements.

� �a E E� �

LiF� �E E� �

Fig. 1. Sketch of crystallization volumes of the LiF–LiBr–LiVO3–Li2SO4 system.

LiBr

LiF

LiVO3

Li2SO4

480

α/β 575

575

591

575

573

849

575

530

497

403

444473 428

423

550

467

a

b

c

C

D

P

RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 55 No. 8 2010

LiF–LiBr–LiVO3–Li2SO4 FOUR�COMPONENT SYSTEM 1289

LiBr

LiFLi2SO4

E1

E2

E3E4

a

b

c

480

550

423

467

849

467

550

428573

591

620473

444

550

480

p 575

858

575

530

LiVO3

LiBrLiBr

a

473

p 575

497

Fig. 2. Development of the boundary elements of the LiF–LiBr–LiVO3–Li2SO4 concentration tetrahedron.

a

b

c

C

D

60%Li2SO4

40% LiF

60%LiVO3

40% LiF

60%LiBr

40% LiF

E1 497

E2

E3

423

428

EE

Fig. 3. Phase diagram of the аbс vertical section of the LiF–LiBr–LiVO3–Li2SO4 system.

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RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 55 No. 8 2010

GUBANOVA et al.

600

500

400

0 3 6 9 12

E

E2E3

L

L + LiF

L + LiF + LiBr

L + LiF + LiBr +LiVO3L + LiF +

LiBr +β�Li2SO4

LiF + LiBr + LiVO3 + β�Li2SO4

423 428

T, °C

C D

LiVO3, mol %40% LiF48% LiBr12% Li2SO4

40% LiF48% LiBr12% LiVO3

403

Fig. 4. Phase diagram of the CD vertical section of the LiF–LiBr–LiVO3–Li2SO4 system.

E

E

L

L + LiF

L + LiF + LiBrL + LiF + LiBr +LiVO3 + β�Li2SO4

600

500

400

48 46 44 42 40 38 36 3460% LiBr40% LiF

LiBr, mol %

T, °C

403

Fig. 5. Phase diagram of the vertical section of the LiF–LiBr–LiVO3–Li2SO4 system.� �a E E� �

a

RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 55 No. 8 2010

LiF–LiBr–LiVO3–Li2SO4 FOUR�COMPONENT SYSTEM 1291

To summarize, we have studied the phase complexof the LiF–LiBr–LiVO3–Li2SO4 four�component sys�tem. The composition, melting temperature, andenthalpy of melting have been determined for thealloys corresponding to the eutectic of the title four�component system. Samples having this compositionare suitable for use as the working body of heat storagesand fused electrolytes in chemical current sources.

ACKNOWLEDGMENTS

This work was fulfilled in the frame of a project ofthe analytical departmental target program “Develop�ment of the Scientific Potential of Higher EducationInstitutions (for 2006–2008).”

REFERENCES

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densed Multinary Systems (Kuibyshev, 1977) [in Rus�sian].

4. The Thermal Constants of Substances. Handbook, Ed. byV. P. Glushko (VINITI, Moscow, 1981), Issue X, Pt. 1[in Russian].

5. G. E. Egortsev, I. K. Garkushin, and I. M. Kondratyuk,Proceedings of VI International Conference “Fundamen�tal Topics of Electrochemical Power Industry” (Saratov,2005), p. 512 [in Russian].

6. The Handbook on Melting of Salt Systems, Ed. byN. K. Voskresenskaya (Akad. Nauk SSSR, Moscow,1961), Vol. 1 [in Russian].

7. Zh. A. Koshkarov, V. I. Lutsyk, M. V. Mokhoseev, et al.,Zh. Neorg. Khim. 32 (6), 1480 (1987).

8. Melting Diagrams of Salt Systems, Ed. by V. I. Posypaikoand E. A. Alekseeva (Metallurgiya, Moscow, 1977) pt. 3[in Russian].

9. Zh. A. Koshkarov, Candidate’s Dissertation in Chemis�try (Inst. of Natural Sciences, Ulan�Ude, 1987).

10. T. V. Gubanova, E. I. Frolov, and I. K. Garkushin,Zh. Neorg. Khim. 54 (5), 851 (2009) [Russ. J. Inorg.Chem. 54 (5), 792 (2009)].

11. E. I. Frolov, T. V. Gubanova, I. K. Garkushin, et al.,RF Pat. 2326920, publ. June 20, 2008.

12. N. A. Vasina, E. S. Gryzlova, and S. G. Shaposhnikova,Thermophysical Properties of Multinary Salt Systems(Khimiya, Moscow, 1984) [in Russian].

L

L + LiF

LiF + LiBr + LiVO3 + β�Li2SO4

E 403

800

700

600

500

400

LiF100 90 80 70 60 50 40 30 20 10

T, °C

LiF, mol %

E

Fig. 6. Phase diagram of the invariant section of the LiF–LiBr–LiVO3–Li2SO4 system.LiF� �E E� �