Glassy Properties of Lead-free Isovalent Relaxor BaZr0.4Ti0.6O3

Glassy dielectric properties were investigated in lead-free BaZr0.4Ti0.6O3 (BZT40) ceramic samples using dielectric spectroscopy in the frequency range of 0.003 Hz-1 MHz and at temperatures of 10 K < T < 300 K. Measurements of the quasistatic dielectric polarization in bias electric fields up to ~28 kV/cm suggested that a ferroelectric state could not be induced, in contrast to the case of canonical relaxors such as PMN. The quasistatic dielectric and freezing dynamics results for the above field amplitudes showed that BZT40 effectively behaves as a dipolar glass. The relaxation spectrum was analyzed employing a frequency-temperature plot, which showed that the longest relaxation time obeyed the Vogel-Fulcher relation tau=tau0exp[E0/(T-T0)], with a freezing temperature of 76.7 K. The shortest relaxation time, in contrast, was characterized by a freezing temperature value close to 0 K, implying an Arrhenius-type behavior. The higher value of the polarization and the nonlinear third-order dielectric coefficient epsilon3 indicated a shift from a pseudospin glass behavior observed for BaZr0.5Ti0.5O3 (BZT50) toward a classical relaxor ferroelectric state.