265

ISSN 0036-0236, Russian Journal of Inorganic Chemistry, 2007, Vol. 52, No. 2, pp. 265–268. © Pleiades Publishing, Inc., 2007.Original Russian Text © T.V. Gubanova, E.I. Frolov, I.K. Garkushin, 2007, published in Zhurnal Neorganicheskoi Khimii, 2007, Vol. 52, No. 2, pp. 308–311.

The title four-component system was studied usingdifferential thermal analysis (DTA). The temperaturegage used was a Pt–Pt/10%Rh thermocouple. Therecorder used was a KSP-4 automated potentiometer.The reference used was freshly calcined

Al

2

O

3

. Thecooling rate was 12–15 K/min. The temperature rangeof the investigation was

400–900°C

.

All compositions are expressed in molar percent. Thetemperature is expressed in Celsius degrees. The samplesize was 0.2 g.

The starting chemicals (high-purity grade Li

2

SO

4

,chemically pure grade

Li

2

CO

3

and

V

2

O

5

, pure for analy-sis LiF, and pure grade

Li

2

MoO

4

) were precalcined.Lithium metavanadate was prepared by the reaction

Li

2

CO

3

+ V

2

O

5

= 2LiVO

3

+ CO

2

.

The powdered reagents (a total of 5 g in weight),taken in the stoichiometric proportion and homoge-nized in an agate mortar, were heated in a platinum cru-cible to

580°ë

. Then, the blend was exposed at this tem-perature for 6 h. The synthesis temperature was deter-mined from the data on the

Li

2

O–V

2

O

5

system [1] andthe DTA heating curve for a stoichiometric mixture ofpowdered

Li

2

CO

3

and

V

2

O

5

. Reagent purity control wasperformed by X-ray powder diffraction on a DRON-3.0diffractometer using

β

-filtered (Ni)

Cu

K

α

radiation.

Quantitative DTA was used to determine the specificenthalpy of melting for the eutectic composition. Ther-mocouples were attached to the bottom of the DTAsetup. Three cooling and heating curves were recordedfor each of the eutectic composition and reference (thereference used was

Na

2

MoO

4

; polymorphic transitionat

451°C, 113.8

J/g [2]). The DTA peak areas were con-fined in accordance with the recommendations of the

ICTA Standardization Committee [3]. The specificenthalpy of melting was calculated from

(1)

Here,

∆

tH

ref

is the specific enthalpy of the phase transi-tion in the reference whose phase-transition tempera-ture is close to that in the test sample, J/g;

S

E

and

S

ref

are, respectively, the DTA peak areas due to the meltingof the eutectic and the phase transition of the reference;and

T

E

and

T

ref

are, respectively, the melting point of theeutectic and the phase-transition temperature in the ref-erence,

°ë

[4]. The final enthalpy value was found asthe average of three measurements.

EXPERIMENTAL

Projective thermogravimetry rules [5] were used inexperimental design for the

Li

||

F, VO

3

, SO

3

, SO

4

,MoO

4

system. The parameters of the phase transitionsin the individual compounds were taken from [2]. Allthe two- and three-component systems that are the faceelements of the

LiF–LiVO

3

–Li

2

SO

4

–Li

2

MoO

4

systemwere studied in [6–10]. The authors refined the param-eters (the melting points and compositions) of thealloys at the invariant points of the two- and three-com-ponent systems (table). The data on the two- and three-component systems are indicated on the developmentof the faces of the concentration tetrahedron (Figs. 1, 2).

Proceeding from the position of the invariant pointsin the low-dimension systems, we chose the following2D vertical section in the lithium fluoride volume:

a

=

[40.0% LiF +

60.0% Li

2

MoO

4

]

,

b

= [40.0% LiF +60.0%

Li

2

SO

4

], and c = [40.0% LiF + 60.0% LiVO

3

](Figs. 2, 3). Then, the 1D section

AB

was chosen in this2D section:

A

= 40.0% LiF + 42.0% LiVO

3

+ 18.0%

∆mHE ∆tHref

SE

Sref--------

tE

tref------, J/g.=

LiF–LiVO

3

–Li

2

SO

4

–Li

2

MoO

4

Four-Component System

T. V. Gubanova, E. I. Frolov, and I. K. Garkushin

Samara State Technical University, Molodogvardeyskaya ul. 244, Samara, 443100 Russia

Received April 18, 2006

Abstract

—The LiF–LiVO

3

–Li

2

SO

4

–Li

2

MoO

4

four-component system was studied using differential thermalanalysis. The eutectic composition was determined (mol %): LiF, 25.0; LiVO

3

, 43.8; Li

2

SO

4

, 14.8; Li

2

MoO

4

,16.5. The eutectic melting point is 428

°

C; the enthalpy of melting is 260 J/g.

DOI:

10.1134/S0036023607020222

PHYSICOCHEMICAL ANALYSISOF INORGANIC SYSTEMS

266

RUSSIAN JOURNAL OF INORGANIC CHEMISTRY

Vol. 52

No. 2

2007

GUBANOVA

et al.

Li

2

SO

4

, and

B

= 40.0% LiF + 42.0% LiVO

3

+ 18.0%Li

2

MoO

4

(Figs. 3, 4).

From the phase diagram of the

AB

section, we deter-

mined the projection of the quaternary eutecticpoint; the composition of this projection was used to

E�

determine the ratio of the lithium molybdate and lith-ium sulfate concentrations in the quaternary eutectic.The fixed ratio of the components (

LiVO

3

: Li

2

MoO

4

:Li

2

SO

4) in the quaternary eutectic in the section abc andthe composition of the quaternary invariant point(table) were determined as a result of the systematic

Characteristics of the invariant points in the two- and three-component systems of the LiF–LiVO3–Li2SO4–Li2MoO4 system

System PointComponents*, mol %

Melting point, °C1 2 3

LiF–LiVO3 [7] Eutectic 23.0 77.0 573

LiF–Li2SO4 [6] EutecticPeritectic

41.026.0

59.074.0

530 575

LiF–Li2MoO4 [7] Eutectic 38.0 62.0 609

LiVO3–Li2SO4 [8] Eutectic 81.0 19.0 591

LiVO3–Li2MoO4 [6] " 73.0 27.0 533

Li2SO4–Li2MoO4 [6] " 62.0 38.0 581

LiF–LiVO3–Li2SO4 [9] EutecticPeritectic

38.03.0

18.0 83.0

44.0 13.5

497 575

LiF–LiVO3– Li2MoO4 [10] Eutectic 18.0 53.0 29.0 493

LiF–Li2SO4– Li2MoO4 [9] EutecticPeritectic

30.11.5

43.461.0

26.537.5

501 575

LiVO3–Li2SO4–Li2MoO4 [10] Eutectic 63.0 15.0 22.0 491

* The components are numbered as they appear in column 1.

530°

LiVO3620°

533°

702°Li2MoO4

858°Li2SO4

575°609°

c

a575°

497°530°

LiF849°

b

581°

573°

591°428°

493°

LiF

LiVO3620°

573°533°

p 575°

858°p 575°

491°

609° 849°Li2MoO4 a

E4

E1

E2

Li2SO4

LiFLiF

530°

609°a702°

849°

b

bc

575°

575°

501° 493°

c581°

E3

591°

573°

849°

497°530°

Fig. 1. Schematics of the phase volumes for the LiF–LiVO3–Li2SO4–Li2MoO4 system.

Fig. 2. Development of the faces of the concentration tetrahe-dron for the LiF–LiVO3–Li2SO4–Li2MoO4 system.

RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 52 No. 2 2007

LiF–LiVO3–Li2SO4–Li2MoO4 FOUR-COMPONENT SYSTEM 267

investigation of the sections Ò– – (Figs. 3, 5) and

LiF– – (Fig. 6).

The tetrahedron of the LiF–LiVO3–Li2SO4–Li2MoO4 system is represented by five crystallizationvolumes due to lithium fluoride, lithium molybdate,lithium metavanadate, α lithium sulfate, and β lithiumsulfate (Fig. 1).

E� E�

E� E�

The specific enthalpy of melting of the eutecticcomposition calculated from the results of three mea-surements was 260 J/g.

In summary, we have studied the LiF–LiVO3–Li2SO4–Li2MoO4 four-component system and experi-mentally determined the composition, melting point,and enthalpy of melting for the eutectic alloy of thissystem.

b

60% LiVO340% LiF

60% Li2MoO440% LiF

ca

B

E1 501°E2 497°

A

60% Li2SO440% LiF

E4 493°

E�

E�

Fig. 3. Phase diagram of the abc isopleth for the LiF–LiVO3–Li2SO4–Li2MoO4 system.

t, °C

400

3 6 9 12 15 18

mol % Li2MoO4

0

497°

600

LiF + LiVO3 + Li2SO4 + Li2MoO4

L + LiF + LiVO3

L + LiF

L

L + LiF +LiVO3 + Li2SO4

493°L + LiVO3

+ LiF + Li2MoO4

BA

E�

40% LiF42% LiVO318% Li2SO4

40% LiF42% LiVO318% Li2MoO4

E2

Fig. 4. Phase diagram of the AB isopleth for the LiF–LiVO3–Li2SO4–Li2MoO4 system.

t, °C

42 40 38 36mol % LiVO3

C

L

400

500

34

LiF + LiVO3 + Li2SO4 + Li2MoO4

L + LiF + LiVO3

L + LiF

60% LiVO340% LiF

E�

E�

Fig. 5. Phase diagram of the Ò– – isopleth for theLiF–LiVO3–Li2SO4–Li2MoO4 system.

E�

E�

t, °C

80 60 40 20mol % LiF

100LiF

500

600

700

800

L + LiF

L

LiF + LiVO3 + Li2SO4 + Li2MoO4

E�

428°E�

Fig. 6. Phase diagram of the LiF– – section for theLiF–LiVO3–Li2SO4–LI2MoO4 system.

E�

E�

268

RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 52 No. 2 2007

GUBANOVA et al.

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