Effect of Copper (II) Oxide on the Microstructure and Phase Transformations of Bismuth Orthoniobate

Abstract

The microstructure and phase transformations of copper atom doped ceramic BiNbO4 synthesized at 950 and 1100°C were studied. According to XPA the samples in compact, pressed form crystallize in the α-BiNbO4 structure irrespective of the synthesis temperature and in spite of the phase transformation α → β at 1040°C. The substances BiNb1–xO4–δ∙xCuO (x ≤ 0.04) are graphite-colored composites with visually expressed grain microstructure. Thermograms of the samples show near 900°C an endo effect associated with the decomposition of the copper (II) oxide and thermal effects due to reconstructive phase transformations of the type α → γ → β in BiNbO4. It was determined that copper oxide impurity in bismuth orthoniobate ceramic acts as a heat sink, which increases the temperature of the phase transition α → γ on heating of compact samples.