On the dielectric strengths of atmospheric plasma sprayed Al2O3, Y2O3, ZrO2-7% Y2O3 and (Ba,Sr)TiO3 coatings

In article an attempt has been made to investigate the dielectric strengths of selected ceramic coatings namely alumina (Al2O3), yttria (Y2O3), YSZ (ZrO2-7% Y2O3) and ferroelectric BST (Ba0.68Sr0.32TiO3) deposited using a atmospheric plasma spray process. Samples of each material were deposited under three different spray distances. The hardness, moduli of elasticity, dielectric strengths of the deposits were evaluated. The microstructures and phases were analyzed using optical microscopy and X-ray diffraction analysis respectively. The results show the significant influence of spray distance on dielectric strengths of the coatings. The dielectric strengths as per hierarchy are 17.3 +/- 1.0 kV/mm for yttria, 16.6 +/- 1.8 kV/mm for alumina, 11.1 +/- 1.5 kV/mm for YSZ and 7.8 +/- 0.8 kV/mm for BST. The particles temperature and velocity during spraying were analyzed in order to find relation between process parameters and dielectric strengths. Correlation between crystallinity of deposited BST and dielectric strength was found in this study. (C) 2015 Elsevier Ltd and Techna Group S.r.l. All rights reserved.