Hydrothermal Synthesis And Structural Chemistry Of Transition Metal Tellurites

The structures and properties of the compounds are profundly affected by the unusual stereochemical effects of the so-call lone-pair elements in heavy p-block elements in lower oxidation states. With the effect of lone-pair, the coordination atoms of heavy p-block elements in lower oxidation states are located the same side, which can lead to reducing the structure dimension. This characteristic can be used as scissors to devise the structure. The research on composite oxides of heavy p-block elements and transition metal elements, especially the early transition metal elements, is an appealing area for their great potential practical applications in many fields, such as catalysis, fast ion conductor, ferroelectric materials, piezoelectric materials, optics materials and so on. Both of two kind ions possess enrich coordination geometries and flexibility conjunct modes. A lot of transition metal tellurites have been reported, but most of them are attained by solid state reactions. Recently, hydrothermal methods have abroad application in the syntheses of inorganic oxide materials. So it is significant to synthesize transition metal tellurites by hydrothermal methods and study the rule of assemble, structure and the relation between structure and properties. This dissertation focuses on the synthesis, structure and characterization of transition metal tellurites; at the same time, we intended to find the relationship between properties and structures. So far we had made achievements on such aspects: (1) we synthesized five novel transition metal tellurites and one compound with Anderson type anion, determined the structure of these compounds by X-ray single crystal diffraction technology. They were: BaV2TeO8(compound(â… )), V₂Te₂O₉(compound(â…¡)), Ba₄LiVTe₉O₂₅ (compound(â…¢)), (NH₄)₃V₆Te₃O₂₁(compound(â…£)), Ba(H₂O)Mo₂Te₂O₁₁(compound(â…¤)), and (pipH₂)₃(Mo₆TeO₂₄)·3(H₂O)(compound(â…¥)). Compound(â… ) compound(â…¡) and compound(â…¢) are vanadium(â…¤) tellurites. Compound(â…£) is mixed valent vanadium tellurite. Compound (â…¤) is formed by molybdenum polyhedra and tellurium polyhedra, which is a kind of compound with second-order nonlinear optical effect. There is plentiful hydrogen bonding in compound(â…¥). (2) The effects of reaction conditions on the outcome phase are considered and studied systematically, and we find a convenient method for synthesizing transition metal tellurites. (3) The Te-O bonds and Te-O polyhedra are classified and reviewed based on summary of literature about tellurites. The relationship between the structure of framework and the linkage of Te-O polyhedra is discussed. (4) The IR and Raman spectra of compound(â… ), compound (â…¡) and compound (â…¤) have been characterized. (5) DSR and fluorescent spectra were employed to characterize compound(â… ), compound (â…¡) and compound (â…¤). But, compound(â… ) and compound (â…¤) do not attain any fluorescent signs. (6) The TGA and DSC were employed to characterize the thermostability and phase-transformation of compound(â… ), compound (â…¡) and compound (â…¤). compound(â… ) and compound (â…¡) are still stable at 800℃. (7) Second-Order Nonlinear Optical property of compound (â…¤) was measured using 1064nm radiation, approximately 1KDF sign was attained. The result confirmed that compound(â…¤) was noncentrosymmetric structure. (8) We calculated and analyzed the energy bands and optical properties of compound(â… ), compound(â…¡) and compound(â…¤), the calculated spectral results are consistent with the experimental results,and the optical results will serve as guidance for the optical experiments.