Subsolidus phase relations in the M 2 MoO 4 -Sc 2 (MoO 4 ) 3 -Hf(MoO 4 ) 2 (M = Li, K) systems have been studied by the method of -intersecting cuts‖. No new triple molybdates have been identified in the Li 2 MoO 4 -Sc 2 (MoO 4 ) 3 -Hf(MoO 4 ) 2 system and a new triple molybdate K 5 ScHf(MoO 4 ) 6 is formed in the K 2 MoO 4 -Sc 2 (MoO 4 ) 3 -Hf(MoO 4 ) 2 system. The structure of K 5 ScHf(MoO 4 ) 6 , have been determined in space group R 3 c through Rietveld analysis of X-ray powder diffraction data. The melting point of molybdate is 999 K. The compound has high ion conductivity (about 10 −3 S/cm).
A series of isostructural trigonal molybdates CsMZr 0.5 (MoO 4 ) 3 with M = Al, Ga, In, Sc, Cr, V, Fe, and CsCrTi 0.5 (MoO 4 ) 3 was synthesized by solid state reactions and characterized by synchrotron powder diffraction, differential scanning calorimetry, thermal conductivity measurements, and magnetization measurements for compounds with a magnetic 3d transition metal cation. The NASICON-type structure of these compounds represents a three-dimensional framework of corner-sharing trigonal MoO 4 -pyramids and MO 6 -octahedra, in which M and Zr (Ti) ions are randomly distributed. The Cs ions occupy large channels along the c-axis. A combination of phenomena like a drastic increase of thermal conductivity, endothermic signals in the DSC curve and anomalies in the thermal expansion coefficients, observed for the compounds with M = Cr, V, Fe, and CsCrTi 0.5 (MoO 4 ) 3 above 700 K, allows one to propose a structural phase transition. The crystal structure of the hightemperature phase is very close to the low-temperature one. A significant hysteresis in high-temperature electronic and thermal conductivity was observed. A possible transition from the piezoelectric to the paraelectric state is discussed.
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