The Positive Temperature Coefficient of Resistivity Effect in the Pb(Fe_1/2Nb_1/2)O₃Ceramics Admixed with Lithium

Abstract

In the paper technological conditions were looked for to obtain the Pb(Fe 1/2 Nb 1/2 )O 3 (PFN) ceramics and the PFN ceramics with the lithium admixture with the highest electric conduction and conditions appropriate for the PTC-R effect formation. Measurements of dc electrical resistivity, dielectric permittivity and dielectric loss were made as functions of temperature from room temperature to 190• C, at 1 kHz. The best set of values of dielectric loss and dielectric constant, from the ferroelectricity point of view, were obtained when the precursor with orthorhombic structure was employed. By creating appropriate technological conditions in the PFN ceramics the PTC-R effect can occur above the Curie temperature. Their electric properties are determined by presence of a basic phase of the potential barrier on the grain boundaries.