Phase stabilization in plasma sprayed BaTiO3

This paper presents a comparison of properties of BaTiO3 ceramics prepared by two different production methods: gas-stabilized plasma spraying (GSP) and spark plasma sintering (SPS). Samples of both materials were evaluated by various techniques, the goal being to detect the Curie temperature of the ferroelectric transformation between the tetragonal and the cubic phase. All tests, resonant ultrasound spectroscopy, dielectric measurements, differential scanning calorimetry and temperature-resolved X-ray diffraction (XRD), used in combination, proved the absence of this transformation in the case of GSP coating up to 500 degrees C. Similarly, the tetragonal-to-orthorhombic transition temperature is shifted downwards, this transition probably taking place in a small fraction of the volume of coating. The SPS samples exhibit several anomalies, such as a strong anisotropy of relative permittivity, but their phase transformations were detected in the usual temperature ranges. (C) 2012 Elsevier Ltd and Techna Group S.r.l. All rights reserved.