Synthesis and structural study of the KNb₄O₆-type compound

Polycrystalline samples with nominal compositions K_1+xNb₄O₆ (0≤x≤1.0) were prepared by the solid-state reaction of KNbO₃, Nb₂O₅ and Mb. Powder X-ray diffraction analysis revealed that the KNb₄O₆-type compound was obtained as the major phase when x≥0.4. Transmission electron microscopy observations showed that when x=0.4, the KNb₄O₆-type compound contained intergrowth defects. In contrast, when x=1.0, practically no intergrowth defects were observed, although this sample contained KNbO₃ as an impurity phase. The relation between the nominal composition and the formation of the intergrowth defects is discussed.