Synthesis, crystal structure and properties of alluaudite-like triple molybdate Na25Cs8Fe5(MoO4)(24)статья
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Дата последнего поиска статьи во внешних источниках: 5 декабря 2014 г.
Аннотация:A new triple molybdate Na25Cs8Fe5(MoO4)(24) was synthesized using solid state reactions and studied with X-ray powder diffraction, second harmonic generation (SHG) technique, differential scanning calorimetry, Mossbauer and dielectric impedance spectroscopy. Single crystals of Na25Cs8Fe5(MoO4)(24) were obtained and its structure was solved (the space group P (1) over bar, a=12.5814(5), b=13.8989(5), c=28.4386(9) angstrom, alpha=90.108(2), beta=90.064(2), gamma=90.020(2), V=4973.0(3) angstrom(3), Z=2, R=0.0440). Characteristic features of the structure are polyhedral layers composed of pairs of edge-shared FeO6 and (Fe, Na)O-6 octahedra, which are connected by bridging MoO4 tetrahedra. The layers share common vertices with bridging MoO4 tetrahedra to form an open 3D framework with the cavities occupied by the Cs+ and Na+ cations. The compound undergoes first-order phase transformation at 642 K and above this phase transition, electrical conductivity reaches 10(-3)-10(-2) S cm(-1). Thus, Na25CS8Fe5(MoO4)(24) may be considered as a promising compound for developing new materials with high ionic conductivity.