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

Abstract

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.