Effect of Mn-acceptor dopant on dielectric and piezoelectric responses of lead lanthanum zirconate titanate piezoceramics

Abstract

Dielectric and direct piezoelectric responses in non-doped and Mn-doped Pb0.91La0.09(Zr0.65,Ti0.35)O3 ceramics are experimentally studied. The permittivity and the direct piezoelectric coefficient were measured by applying an ac electric field or a mechanical stress, respectively. The results show that the dielectric response is mainly due to an extrinsic contribution at room temperature. A notable reduction in room temperature dielectric losses by Mn-doping is verified. The temperature of the minimum of the losses depends on the Mn-content, enabling the Pb0.91La0.09(Zr0.65,Ti0.35)O3 properties to be tuned from soft to hard. A significant stabilization of the dielectric and piezoelectric responses, related to domain wall motion reduction, is confirmed in Mn-doped materials, so these materials become good candidates for transducer applications. The correlation between the dielectric constant and dielectric losses is discussed in terms of the Rayleigh model. Results show that Mn-doped PLZT response does not fit this model. This fact could be explained by taking into account the nature of the defects created by manganese addition. These complex defects act as pinning centers, and the reversible movement of domain walls provide a significant contribution to the response of these materials.