Preparation and dielectric properties of BaZr_0.1Ti_0.9O₃ ceramics with different grain sizes

Abstract

BaZr_0.1Ti_0.9O₃ ceramics with grain sizes of 0.75 and 2.60 µm have been prepared via solid-state reaction. Optimum parameters for calcination and sintering have been found in order to obtain pure perovskite phase, high density ceramics and homogeneous microstructures. The dielectric data show a diffuse phase transition with a mixed ferroelectric-relaxor character at a maximum at 87–92°C, with a small thermal hysteresis of 2–3°C. A tendency towards a more diffuse character of the ferro–para phase transition towards the full relaxor behaviour is observed as small in the ceramic grain size. Better dielectric properties in the coarse ceramics with higher permittivity up to 14,000 at the transition temperature by comparison with 5000 for the fine one, are observed as a consequence of higher tetragonal distortion and higher density. The differences in the dielectric spectra found for the two grain sizes were interpreted as a consequence of the higher degree of inhomogeneity in the fine ceramics and to different grain boundary properties induced by the different sintering temperatures.

Keywords:

• BaTiO₃ solid solution
• Ferroelectric relaxor
• Lead-free material

Acknowledgements

This study was partially supported by INSTM Italy (FISR 2002, University of Genoa, Italy), CNCSIS Romanian grants and COST-539 Action (STSM-539-01859 at ISTEC-CNR Faenza, Italy).