Synthesis, Structure, and Investigation of Bismuth Niobate Doped by Alkaline-Earth Elements

Polycrystalline samples with general formula Bi 3-x M x NbO 7-δ (M = Ba, Ca, Mg, or Sr; x = 0, 0.1) were obtained by solid state method. Single phase compounds are niobates doped by strontium and calcium. A major phase has a tetragonal structure (space group I-4m2) after annealing at 850 ∘ C, which completely transfers into a cubic one (space group Fm3m) after 1000 ∘ C. Dense sintered ceramics were prepared with thermal expansive coefficient equal to 10 × 10 -6 ∘ C -1 . The electroconductivity values of the pure bismuth niobate with a tetragonal structure are higher than those of the one with a cubic structure. However, such tendency does not remain for the bismuth niobate doped by calcium.The work was carried out within the framework of the state task of the Ministry of education and science of the Russian Federation № 4.2288.2017/PCh