Reduction of Dielectric Losses in Pb(Fe1/2Nb1/2)O3-Based Ferroelectric Ceramics

Abstract

Pseudoternary Pb(Fe1/2Nb1/2)O3–PbZrO3–PbTiO3 (PFN–PZ–PT) ferroelectric ceramics with a pure perovskite phase were fabricated by a conventional solid-state reaction method via a B-site oxide mixing route in the whole composition range. The ceramics obtained exhibit marked frequency-dependent dielectric behavior and a large dielectric loss when the concentration of Pb(Fe1/2Nb1/2)O3 exceeds 40 mol %. The large dielectric loss is thought to correlate with the thermally activated hole conduction induced by the partial reduction of Fe3+ to Fe2+ ions during sintering, which can be greatly decreased by adding a small amount of MnO2 or by cycling under an alternating electric field. The values of the dielectric constant and the frequency-dependent dielectric behavior at temperatures around and below the temperatures of the dielectric maximum (Tm) are reduced accordingly. The decrease in dielectric loss is believed to be related to the ionization of the manganese-substituted donor defects. The effect of manganese doping on the depression of mechanical vibration loss also contributes little to the decrease in total dielectric loss through pinning down the rotation of space-charge polarization induced by the combining of complex manganese-substituted defects (Mn2+) with oxygen vacancies and standing near the grain boundaries.