Relaxor properties of Ba(Zr,Ti)O3 ceramics

BaZrxTi1-xO3 is a possible candidate as environmental friendly electroceramic material (Pb-free ferroelectric) due to its high dielectric and piezoelectric constants and ferroelectric properties in a temperature range which can be tuned by the composition. Its properties change from full ferroelectric behavior (x=0; BaTiO3) with a sharp ferro-para phase transition to the full relaxor state (for 0.10<=x<=0.35), when the structure is pseudo-cubic and the transition has a strong diffuse character and a frequency-relaxation in the kHz range. In the present work, the cross-over composition BaZr0.1Ti0.9O3 was investigated. The ceramics have been prepared via solid state reaction; optimum parameters for calcination and sintering in order to obtain pure perovskite phase and a good densification have been found. The temperature dependence of the dielectric constant shows a diffuse phase transition with a small shift of the temperature corresponding to the maximum permittivity of (1-2) °C in the frequency range of 1 Hz÷1 MHz. The losses are smaller than 30% for temperatures below 130 °C, with a slight increasing at low frequency and high temperatures. The real part of the permittivity follows the Curie-Weiss law with frequency-dependent constants. The dielectric spectroscopy data show at least two relaxation processes: a thermally-activated one characteristic to low-frequency range f<100 Hz and a temperature-independent one at f>=100 Hz.