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Phase diagram for the system Bi2O3CaOSrOCuO in the SrO-rich region
Eur. J. Solid State hot-g.
Chem.
t. 35, 1998, p. 591-594
Phase diagram for the system BizO&aO-SrO-CuO in the SrO-rich region B.V. SLOBODIN, V.G. VASSILIEV and E.E. SOLDATOVA Institute of Solid State Chemistry, Ural Division of the Russian Academy of Sciences, Ekaterinburg, 620219, Russia WT., received May 4, 1998; accepted September 24, 1998.)
ABSTRACT. - It has been found experimentally that phase diagram for the system Biz03-CaO-SrQ-CuO in &O-rich region at 850°C in the open air includes three elementary tetrahedra: Ca0-SrO-Sr6Biz011-Sr2CU03, Ca0-SrzCu03-Sr6Biz011-Sr&a0.5Bi207 and Sr3BizOs-SrJ3izOll-Sr3JCa0,5Bi20T S&uO,. In the considered interval of corresponding oxide concentrations quatemary oxides are not formed under the above conditions.
INTRODUCTION There is no phase diagram for equilibrium of the four-component system Biz03-CaO-SrO-CuO in the literature. Only a small number of threecomponent diagrams have been reported [ 11. They represent different sections of tetrahedronof the above system, these sections being studied at different temperatures. Some elementary tetrahedra have also been found [2,3]. But, in general, these diagramsare approximate and do not reflect the complicated characterof phaseequilibria in four-componentsystem. There are some basic points which make it diffkult to construct phase diagram for the system BizOs-CaO-SrO-CuOaccurately.Namely, a) a complex phasecomposition of boundary binary and ternary systemsnot completely examined up to now; b) dependenceof phase composition upon the temperatureand ~(0~); c) tendency of Cu and Bi under certain conditions Eur. J. Solid State Inorg. Chem., 0992-4361/98/8-9/O Elsevier, Paris
592
B.V. SLOBODIN
et
al.
to oxidation-reduction reactions that result in transformation of the fourcomponent system into more complex one; d) among the interaction products there are several multicomponent solid solutions, some compounds with regions of homogeneity as well as incongruently melting compounds. It is hardly probable to consider and to overcome all the above difliculties and to construct a correct diagram. One can only say about its fragments or schemes constructed on the base of some assumptionsand stipulations. The present paper aims to construct the phase diagram for the system Bi203-CaO-SrO-CuO in the SrO-rich region. The solution of this problem has become possible due to the fact that the phase diagrams for the ternary systems CaO-SrO-CuO [4], Bi203-CuO-SrO [5,6], Bi203-CaO-CuO [7] and Bi20&a0-SrO [8,9] have been recently investigated. According to the results of [4-91, near SrO at 830-850°C there are three-component fields CaO-SrO-Sr6Bi20ir, CaO-Sr6Bi20ir-A (hereinafter referred to A= solution Sr3,$&Bi207 as the extreme composition of solid Sr~,~&ao,~+,Bi,O~[9]), A-Sr3Bi206-Sr6Bi20r1 (Bi20&aO-SrO system); CaO-Sr2Cu0&0 (CaO-SrO-CuO system); SrO-Sr6Bi201,-Sr2Cu03 and Sr2Cu03-Sr6Bi201r-Sr3Bi206(Bi20&u0-SrO system). Based on the existence of these fields a part of the phase diagram for the system Bi203CaO-SrO-CuO was divided into elementaryphasetetrahedra. RESULTS AND DISCUSSION 15 samples were synthesized and their figurative points are both inside the tetrahedra assumed and on the sides of the above-mentioned threecomponentfields (Table I). TABLE I - Nominal stoichiometry and experimentally found phase composition of the samplesstudied. 1 2 3 4 5 6 7
CaO + SrO SrO + Sr6Bi2011 SrO + SrzCu03 CaO + Sr6BizO1t CaO + Sr$uOj Srd3izOll + S&u03 CaO+SrO+SrsBiz0,1+SrKu03
8 9
10 11 12 13 14 15
Sr6Bi2011+ A A + Sr$uO.? SaBi206 + SrzCu03 Sr,Bi,O, + A Sr3Bi206+ Sr6Bi20,1 A+Sr&i2011+Sr2Cu03+Sr3Bi206 A+CaO A+ SrcB1201~+SrlCuOs+CaO
Synthesis was carried out in two stages.Wet chemical method was used for obtaining precursors which were then heat-treated.This method consists in
TOME 35 -
1998 -
No' 8-y
BizOj-CaO-SrO-CuO SYSTEMINTHESIO-RICHREGION
593
quantitative precipitation of all the components horn aqueous solution: at first hydroxy salts of bismuth and copper (the pH of the solution was adjusted by the addition of CaC03 and SrCO3) and then hydrous nitrates of calcium and strontium followed by evaporation to dryness of heterogeneous mixture. The concentration of bismuth and copper in solution was calculated as a function of pH according to the formulae: Cui = [Bi3’] (1+iIZEPi&Bi3’]i-*[OH-]i) Cc” = [Ch2’] ( l+iCIZ/3ij[Cu2’]‘-’ [OR]‘), where Cui and Cc” are overall concentration of bismuth and copper respectively in the solution as the amount of metal ions and hydroxocomplexes and pi,j is the formation constant of the hydroxocomplex Mi(OH)j , M=Bi,Cu. This preliminary calculation showed that when pH>5 both components could be precipitated completely as hydroxy salts. The compounds of bismuth and copper, therefore, are precipitated from the solution of nitrates of these elements by adding CaC03 and SrC03, with soluble nitrates of Ca and Sr being present in liquid phase. Following evaporation, drying and dehydration at 2OO’C result in fine-dispersed homogeneous powder that is a mixture of all four element compounds, stoichiometty of which corresponds to the initial ratio. Precursors obtained were annealed in air at 850°C for 15-20 h with intermediate regrinding. Quenching of the samples to avoid oxidation of some compounds was immediately followed by X-ray diffraction analysis (using DRON-2 diffractometer with Cu K, radiation). To identify resulting phases, X-ray diffraction spectra of CaO, SrO, Sr,CuO,, Sr6Bi201r, Sr3Bi206[9-121 and
Fig. 1 - Phase diagram scheme for B&O,-CaO-SrO-CuO 85O”C, p(O9=0.21 atm); A= Sr3.5Ca0.JBi207.
EUR.J.SOLlD
STATE INORG.CHEM.
system in the SrO-rich region (T=
594
B.V. SLOBODIN
et al.
Sr3.-$a,,5Bi207[9] were used. The experimentally found phase composition of all samplesstudied agreedwith their nominal stoichiometry (Table I). Analysing the results obtained we have come to the following conclusion: phase diagram for the system Bi203-CaO-SrO-CuO in the SrO-rich region includes three elementary tetraheda (Fig. 1): CaO-SrO-Sr6Bi201,- Sr2Cu03, CaO- Sr2Cu03-SreBi20r1-A and Sr3Bi206-Sr6BiZOI,-A- Sr&uO3. In the considered interval of component concentrations under the above conditions quaternary oxides containing B&03, CaO, SrO, CuO are not formed. Formally this concentration region does not belong to the fourcomponent system since oxide Sr6Bi‘20 11~ which is stable at 850°C in the open air, contains pentavalent bismuth; neverthelesswe place this region on our diagram, becausefive-component diagram turns out to be too complex to be useful.
REFERENCES [I] P. MAJEWSKI,
B.FREILINGER,
BHETTICH,
T.POPP and XSCHULZE , High R.Fliikiger and
Temp. Superconductors Materials Aspects, Ed.: H.C.Freyhardt,
M.Peukert, Verlag, FRG, 1991, 1, p.393. [2] B.HONG, JHAHN and T.O.MASON, J. Am. Cerum. Sot., 1990,73, p. 1965. [3] G.E.NIKIFOROVA and G.D.NIPAN, Dokl. Akad. Nauk, 1997,356, p.354. [4] B.V.SLOBODIN, A.A.FOTIEV and N. A.PAKHOMOVA, Zh. Neorg Khim., 1992,37, p.1374. [5] B.V.SLOBODIN, I.A.OSTAPENKO and A.A.FOTIEV, Zh. Neorg. Khim., 1992,37, p.438. [6] J.A.SAGGIO, KSUJATA, JHAHN, S.J.HWU, K.R.POEPPELMEIER and T.O.MASON,J. Am. Cevam. Sot., 1989, 72, p.849. [7] B.V.SLOBODIN, A.A.FOTIEV and N.A.PAKHOMOVA, Zh. Neorg. Khim., 1991,36, p.510. [8] B.V.SLOBODIN and A.A.FOTIEV, Zh. Neorg. Khim., 1994,39, p. 1198. [9] B.V.SLOBODIN, V.G.VASSILIEV and E.E.SOLDATOVA, Zh. Neorg. Khim., 1997, 42, p. 1740. [lo] Database JCPDSD-ICDD (USA), copyright 1995.. [ll] W.K.WONG-NG, K.L.DAVIS andR.S.ROTH, J Am. Cerum. Sot.. 1988,71, p.C64. [ 121 F.ABBAITISTA, C.BRISI, D.MAZZA and M.VALLINO, Mat. Rex Bull., 199 I, 26, p.107.
TOME 35 -
1998 -
No” 8-9
Chem.
t. 35, 1998, p. 591-594
Phase diagram for the system BizO&aO-SrO-CuO in the SrO-rich region B.V. SLOBODIN, V.G. VASSILIEV and E.E. SOLDATOVA Institute of Solid State Chemistry, Ural Division of the Russian Academy of Sciences, Ekaterinburg, 620219, Russia WT., received May 4, 1998; accepted September 24, 1998.)
ABSTRACT. - It has been found experimentally that phase diagram for the system Biz03-CaO-SrQ-CuO in &O-rich region at 850°C in the open air includes three elementary tetrahedra: Ca0-SrO-Sr6Biz011-Sr2CU03, Ca0-SrzCu03-Sr6Biz011-Sr&a0.5Bi207 and Sr3BizOs-SrJ3izOll-Sr3JCa0,5Bi20T S&uO,. In the considered interval of corresponding oxide concentrations quatemary oxides are not formed under the above conditions.
INTRODUCTION There is no phase diagram for equilibrium of the four-component system Biz03-CaO-SrO-CuO in the literature. Only a small number of threecomponent diagrams have been reported [ 11. They represent different sections of tetrahedronof the above system, these sections being studied at different temperatures. Some elementary tetrahedra have also been found [2,3]. But, in general, these diagramsare approximate and do not reflect the complicated characterof phaseequilibria in four-componentsystem. There are some basic points which make it diffkult to construct phase diagram for the system BizOs-CaO-SrO-CuOaccurately.Namely, a) a complex phasecomposition of boundary binary and ternary systemsnot completely examined up to now; b) dependenceof phase composition upon the temperatureand ~(0~); c) tendency of Cu and Bi under certain conditions Eur. J. Solid State Inorg. Chem., 0992-4361/98/8-9/O Elsevier, Paris
592
B.V. SLOBODIN
et
al.
to oxidation-reduction reactions that result in transformation of the fourcomponent system into more complex one; d) among the interaction products there are several multicomponent solid solutions, some compounds with regions of homogeneity as well as incongruently melting compounds. It is hardly probable to consider and to overcome all the above difliculties and to construct a correct diagram. One can only say about its fragments or schemes constructed on the base of some assumptionsand stipulations. The present paper aims to construct the phase diagram for the system Bi203-CaO-SrO-CuO in the SrO-rich region. The solution of this problem has become possible due to the fact that the phase diagrams for the ternary systems CaO-SrO-CuO [4], Bi203-CuO-SrO [5,6], Bi203-CaO-CuO [7] and Bi20&a0-SrO [8,9] have been recently investigated. According to the results of [4-91, near SrO at 830-850°C there are three-component fields CaO-SrO-Sr6Bi20ir, CaO-Sr6Bi20ir-A (hereinafter referred to A= solution Sr3,$&Bi207 as the extreme composition of solid Sr~,~&ao,~+,Bi,O~[9]), A-Sr3Bi206-Sr6Bi20r1 (Bi20&aO-SrO system); CaO-Sr2Cu0&0 (CaO-SrO-CuO system); SrO-Sr6Bi201,-Sr2Cu03 and Sr2Cu03-Sr6Bi201r-Sr3Bi206(Bi20&u0-SrO system). Based on the existence of these fields a part of the phase diagram for the system Bi203CaO-SrO-CuO was divided into elementaryphasetetrahedra. RESULTS AND DISCUSSION 15 samples were synthesized and their figurative points are both inside the tetrahedra assumed and on the sides of the above-mentioned threecomponentfields (Table I). TABLE I - Nominal stoichiometry and experimentally found phase composition of the samplesstudied. 1 2 3 4 5 6 7
CaO + SrO SrO + Sr6Bi2011 SrO + SrzCu03 CaO + Sr6BizO1t CaO + Sr$uOj Srd3izOll + S&u03 CaO+SrO+SrsBiz0,1+SrKu03
8 9
10 11 12 13 14 15
Sr6Bi2011+ A A + Sr$uO.? SaBi206 + SrzCu03 Sr,Bi,O, + A Sr3Bi206+ Sr6Bi20,1 A+Sr&i2011+Sr2Cu03+Sr3Bi206 A+CaO A+ SrcB1201~+SrlCuOs+CaO
Synthesis was carried out in two stages.Wet chemical method was used for obtaining precursors which were then heat-treated.This method consists in
TOME 35 -
1998 -
No' 8-y
BizOj-CaO-SrO-CuO SYSTEMINTHESIO-RICHREGION
593
quantitative precipitation of all the components horn aqueous solution: at first hydroxy salts of bismuth and copper (the pH of the solution was adjusted by the addition of CaC03 and SrCO3) and then hydrous nitrates of calcium and strontium followed by evaporation to dryness of heterogeneous mixture. The concentration of bismuth and copper in solution was calculated as a function of pH according to the formulae: Cui = [Bi3’] (1+iIZEPi&Bi3’]i-*[OH-]i) Cc” = [Ch2’] ( l+iCIZ/3ij[Cu2’]‘-’ [OR]‘), where Cui and Cc” are overall concentration of bismuth and copper respectively in the solution as the amount of metal ions and hydroxocomplexes and pi,j is the formation constant of the hydroxocomplex Mi(OH)j , M=Bi,Cu. This preliminary calculation showed that when pH>5 both components could be precipitated completely as hydroxy salts. The compounds of bismuth and copper, therefore, are precipitated from the solution of nitrates of these elements by adding CaC03 and SrC03, with soluble nitrates of Ca and Sr being present in liquid phase. Following evaporation, drying and dehydration at 2OO’C result in fine-dispersed homogeneous powder that is a mixture of all four element compounds, stoichiometty of which corresponds to the initial ratio. Precursors obtained were annealed in air at 850°C for 15-20 h with intermediate regrinding. Quenching of the samples to avoid oxidation of some compounds was immediately followed by X-ray diffraction analysis (using DRON-2 diffractometer with Cu K, radiation). To identify resulting phases, X-ray diffraction spectra of CaO, SrO, Sr,CuO,, Sr6Bi201r, Sr3Bi206[9-121 and
Fig. 1 - Phase diagram scheme for B&O,-CaO-SrO-CuO 85O”C, p(O9=0.21 atm); A= Sr3.5Ca0.JBi207.
EUR.J.SOLlD
STATE INORG.CHEM.
system in the SrO-rich region (T=
594
B.V. SLOBODIN
et al.
Sr3.-$a,,5Bi207[9] were used. The experimentally found phase composition of all samplesstudied agreedwith their nominal stoichiometry (Table I). Analysing the results obtained we have come to the following conclusion: phase diagram for the system Bi203-CaO-SrO-CuO in the SrO-rich region includes three elementary tetraheda (Fig. 1): CaO-SrO-Sr6Bi201,- Sr2Cu03, CaO- Sr2Cu03-SreBi20r1-A and Sr3Bi206-Sr6BiZOI,-A- Sr&uO3. In the considered interval of component concentrations under the above conditions quaternary oxides containing B&03, CaO, SrO, CuO are not formed. Formally this concentration region does not belong to the fourcomponent system since oxide Sr6Bi‘20 11~ which is stable at 850°C in the open air, contains pentavalent bismuth; neverthelesswe place this region on our diagram, becausefive-component diagram turns out to be too complex to be useful.
REFERENCES [I] P. MAJEWSKI,
B.FREILINGER,
BHETTICH,
T.POPP and XSCHULZE , High R.Fliikiger and
Temp. Superconductors Materials Aspects, Ed.: H.C.Freyhardt,
M.Peukert, Verlag, FRG, 1991, 1, p.393. [2] B.HONG, JHAHN and T.O.MASON, J. Am. Cerum. Sot., 1990,73, p. 1965. [3] G.E.NIKIFOROVA and G.D.NIPAN, Dokl. Akad. Nauk, 1997,356, p.354. [4] B.V.SLOBODIN, A.A.FOTIEV and N. A.PAKHOMOVA, Zh. Neorg Khim., 1992,37, p.1374. [5] B.V.SLOBODIN, I.A.OSTAPENKO and A.A.FOTIEV, Zh. Neorg. Khim., 1992,37, p.438. [6] J.A.SAGGIO, KSUJATA, JHAHN, S.J.HWU, K.R.POEPPELMEIER and T.O.MASON,J. Am. Cevam. Sot., 1989, 72, p.849. [7] B.V.SLOBODIN, A.A.FOTIEV and N.A.PAKHOMOVA, Zh. Neorg. Khim., 1991,36, p.510. [8] B.V.SLOBODIN and A.A.FOTIEV, Zh. Neorg. Khim., 1994,39, p. 1198. [9] B.V.SLOBODIN, V.G.VASSILIEV and E.E.SOLDATOVA, Zh. Neorg. Khim., 1997, 42, p. 1740. [lo] Database JCPDSD-ICDD (USA), copyright 1995.. [ll] W.K.WONG-NG, K.L.DAVIS andR.S.ROTH, J Am. Cerum. Sot.. 1988,71, p.C64. [ 121 F.ABBAITISTA, C.BRISI, D.MAZZA and M.VALLINO, Mat. Rex Bull., 199 I, 26, p.107.
TOME 35 -
1998 -
No” 8-9