Phase formation in the systems Ag2MoO4–MO–MoO3 (M=Ca, Sr, Ba, Pb, Cd, Ni, Co, Mn) and crystal structures of Ag2M2(MoO4)3 (M=Co, Mn)
| Autor: | Zh. G. Bazarova, Sergey F. Solodovnikov, Zoya A. Solodovnikova, E. T. Khobrakova, Elena G. Khaikina, G. D. Tsyrenova |
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| Rok vydání: | 2004 |
| Předmět: |
Phase transition
Inorganic chemistry Oxide Crystal structure Condensed Matter Physics Electronic Optical and Magnetic Materials Ion Inorganic Chemistry Crystallography chemistry.chemical_compound chemistry Octahedron Materials Chemistry Ceramics and Composites Physical and Theoretical Chemistry Thermal analysis Ternary operation Eutectic system |
| Zdroj: | Journal of Solid State Chemistry. 177:2158-2167 |
| ISSN: | 0022-4596 |
| DOI: | 10.1016/j.jssc.2004.01.002 |
| Popis: | Phase equilibria in the systems Ag2MoO4–MMoO4 (M=Ca, Sr, Ba, Pb, Ni, Co, Mn) and subsolidus phase relations in the systems Ag2MoO4–MO–MoO3 (M=Ca, Pb, Cd, Mn, Co, Ni) were investigated using XRD and thermal analysis. The systems Ag2MoO4–MMoO4 (M=Ca, Sr, Ba, Pb, Ni) belong to the simple eutectic type whereas in the systems Ag2MoO4–MMoO4 (M=Co, Mn) incongruently melting Ag2M2(MoO4)3 (M=Co, Mn) were formed. In the ternary oxide systems studied no other compounds were found. Low-temperature LT-Ag2Mn2(MoO4)3 reversibly converts into the high-temperature form of a similar structure at 450–500°C. The single crystals of Ag2Co2(MoO4)3 and LT-Ag2Mn2(MoO4)3 were grown and their structures determined (space group P 1 , Z=2; lattice parameters are a=6.989(1) A, b=8.738(2) A, c=10.295(2) A, α=107.67(2)°, β=105.28(2)°, γ=103.87(2)° and a=7.093(1) A, b=8.878(2) A, c=10.415(2) A, α=106.86(2)°, β=105.84(2)°, γ=103.77(2)°, respectively) and refined to R(F)=0.0313 and 0.0368, respectively. The both compounds are isotypical to Ag2Zn2(MoO4)3 and contain mixed frameworks of MoO4 tetrahedra and pairs of M2+O6 octahedra sharing common edges. The Ag+ ions are disordered and located in the voids forming infinite channels running along the a direction. The peculiarities of the silver disorder in the structures of Ag2M2(MoO4)3 (M=Zn, Mg, Co, Mn) are discussed as well as their relations with analogous sodium-containing compounds of the structural family of Na2Mg5(MoO4)6. The phase transitions in Ag2M2(MoO4)3 (M=Mg, Mn) of distortive or order–disorder type are suggested to have superionic character. |
| Databáze: | OpenAIRE |
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