新しいニオブ酸化物の探査と結晶構造

抄録

We review preparations and crystal structures of various kinds of new niobium oxides. Ilmenite-type ANbO₃ (A=Li, Na), which were prepared by low temperature hydrothermal reaction and ion-exchange reaction, are the first examples of ilmenite-type niobium oxides. These niobium oxides are metastable phases and transform into the stable phases at elavated temperatures. A new reduced niobium oxide, Rb_1.51Nb₁₀O₁₇ has a Nb₆O₁₂ cluster characteristic of strongly reduced niobium oxides. Weakly reduced niobium oxides, K₂YNb₅O_15-δ and K₆Nb_10.9O₃₀ have NaNb₆O₁₅F-type and tetragonal tungsten bronze type strcutures, respective-ly. In the A₂O-MO- Nb₂O₅ (A=K, Rb, Cs; M=Mg, Fe) system, two types of compounds K₂M₂Nb₄O₁₃ and A (M, Nb) ₂O₅, which are isostructural with K₂Ti₆O₁₃ and KTiNbO₅ respectively, were obtained.