Synthesis and Properties of Alkali/Alkaline Earth Niobates with the Tetragonal Potassium-Tungsten Bronze Structure.

Polycrystalline samples of the compounds A//2**IA//4**I**INb//1//0O//3//0 with the tetragonal potassium-tungsten bronze structure have been obtained by solid-phase synthesis. The temperatures of their ferroelectric phase transitions and certain parameters of their band structure have been determined. The electric conductivity of the compounds A//2**IA//4**I**INb//1//0O//3//0 below 900 K is impurity electronic. The possibilities of directed modification of the properties of alkali/alkaline earth niobates by heterovalent cation substitution are limited, due to the comparatively high probability of the formation of V//A//I.