Browsing by Author "Wang, Shumin"

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    Synthesis and characterization of reduced titanium silicate and phosphate compounds with mixed-framework structures
    (1993) Wang, Shumin
    A number of significant research accomplishments have been made concerning the synthesis of new solid state materials that have interesting and important structural chemistry and physical properties; namely compounds with mixed TiO$\sb6$ octahedra and XO$\sb4$ (X = Si and P) tetrahedra: BaTi$\sb2$(P$\sb2$O$\sb7)\sb2$, A$\sp{\rm I}$TiP$\sb2$O$\sb7$ (A$\sp{\rm I}$ = Li, K, Cs, Rb), and TiP$\sb3$SiO$\sb{11}$. The LISICON series: Li$\sb{1 + x}$Ti$\sb2$(PO$\sb4)\sb3$ (0 $\le {x} \le$ 2), and oxo compounds with novel quasi-two-dimensional fused TiO$\sb6$ framework: La$\sb4$Ti(Si$\sb2$O$\sb7)\sb2$(TiO$\sb2)\sb{\rm 4m}$ (m = 1, 2) series have also been prepared and studied. For the first time, LISICON phases provide a series of compounds with pseudo-one-dimensional channel structures for systematic ionic conductivity and structure relationship studies. The oxo compound series possesses a quasi-two-dimensional structural property in that the low-valent conducting TiO$\sb6$ octahedral (rutile) framework is sandwiched by insulting oxosilicate slabs. Structurally, the preserved Ti-O-Ti and Ti-Ti linkages in the fused rutile frameworks are deemed important to the mechanistic studies of the transport properties which are induced by conduction electrons. In the exploratory syntheses of the above compounds, a conventional high-temperature solid-state ceramic method, and a molten salt flux crystal growth method have been employed. The structures of these compounds were characterized by both single crystal and powder X-ray diffraction techniques. The Weissenberg film technique was employed for the crystallographic studies. Other techniques for the structure/property characterization were also used. It has been demonstrated that the reduced titanium silicates and phosphates are new and fruitful areas of research which provides us with some insight and new direction towards the success of the synthesis of compounds with low-dimensional structures. Our success offers opportunities for finding structural models to study many unusual physical phenomena including superconductivity. Ultimately this research should lead us towards a better understanding of the structure, bonding and property correlations of metallic oxides and advanced materials.