Relaxation currents in morphotropic region of Pb[(Fe_1/3Sb_2/3)_xTi_yZr_z]O₃ ferroelectric ceramics

Abstract

Studies on the dielectric relaxation currents in the morphotropic region of Pb[(Fe_1/3Sb_2/3) _x Ti _y Zr _z ]O₃ with x + y + z = 1, x = 0.1 and y = 0.44–0.46 are presented. The measurements have been performed at three poling fields, i.e. (a) 0.02 kV cm⁻¹ that is much lower than the coercive force (8 kV cm⁻¹), (b) 10 kV cm⁻¹, i.e. slightly above the coercive force and (c) much higher field (20 kV cm⁻¹). There were measured transient polarisation and depolarisation currents. For a low poling field, these currents do not differ from each other, but for higher fields the difference increases with increasing poling field. The analysis of depolarisation current data obtained at various temperatures (298–473 K) shows that relaxation time τ_p varies exponentially with temperature. The activation energies calculated for samples with y = 0.44, 0.45 and 0.46 equals to 0.26, 0.24 and 0.22 eV, respectively. The defect dipole ) complex and the Dissado–Hill double-minimum potential models are proposed to explain the observed relaxation behaviour in Pb[(Fe_1/3Sb_2/3) _x Ti _y Zr _z ]O₃ ferroelectric ceramics.

Keywords:

• ferroelectric ceramics
• PZT
• relaxation currents
• morphotropic phase