Charge Compensation Mechanism Decreases Dielectric Loss in Manganese-Doped Pb(Fe1/2Nb1/2)O3 Ceramics

Abstract

Mn-doped Pb(Fe1/2Nb1/2)O3 (PFN) ceramics are synthesized by the conventional solid-state reaction method via a B-site oxide mixing route. The pure perovskite phase of Mn-doped PFN is obtained up to 0.75 mol% of manganese doping. Due to manganese doping, dielectric loss of the obtained ceramics decreases continuously up to 3 mol% of manganese, although pyrochlore phase appears. The decrease of dielectric loss can be explained by the charge compensation effect caused by the substitution of Mn4+ for Fe3+ in the octahedral cage of the perovskite structure, which is confirmed by X-ray photoelectron spectrometry (XPS). That is, due to the substitution of Mn4+ for Fe3+ ions, the relative content of iron in different valence states changes, i.e., the relative content of Fe2+ ions increases with the amount of doped manganese. Therefore, the hole-conduction mechanism caused by the partial reduction of Fe3+ to Fe2+ in the PFN system weakens, which leads to the decrease of dielectric loss. The effect of manganese doping on the depression of mechanical vibration loss also provides some contribution to the decrease of total dielectric loss through pinning down the rotation of spontaneous polarization induced by combining Mn2+ (reduced of doped Mn4+ ions during sintering) with the oxygen vacancy (produced by the compensation effect) and standing near the domain boundary. The relative dielectric constant of the Mn-doped PFN ceramics also decreases continuously with the increase of manganese content, which is believed to be related to the reduction of space-charge polarization.