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摘要: 利用水热法合成了立方相KNb0.77Al0.23O2.77。在水热晶化过程中得到了包括正交相钙钛矿和一新相在内的中间相产物。结构相变行为采用XRD、DSC、高压Raman和XPS进行了表征。结果表明,低于1 000 ℃的热处理不能导致KNb0.77Al0.23O2.77发生结构相交。而在4.49 PGa高压下可能发生了到一新相的结构转变。高温高压处理可以导致另一新相的出现。最后对该立方相的相变机理进行了研究。Abstract: Various products including cubic KNb0.77Al0.23O2.77 and orthorhombic KNbO3 were hydrothermally synthesized. Structural evolution behaviors of the cubic were examined by means of X-ray diffraction (XRD), differential scanning calorimeter (DSC), high pressure Raman spectroscopy, Infrared (IR), and X-ray photoelectron spectroscopy (XPS). Another new phase appeared during the pressure-induced structural transition of the cubic at a pressure of 4.49 GPa. High temperature and high pressure treatments resulted in a third new phase by adjusting effectively the number of electrons flowing between Nb-O as well as hybridization between p electrons of oxygen and d electrons of Nb ions. During the structural transition, the reduction of Nb (Ⅴ) to Nb (Ⅳ) occurred as well as oxygen vacncies in the cubic lattice. The stabilization and transition mechanisms are discussed.
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