Ferroelectric-to-relaxor transition behaviour of BaTiO₃ ceramics doped with La(Mg_1/2Ti_1/2)O₃

Low-frequency dielectric studies were performed on the fine-grain ceramics of BaTiO₃ doped with 2.5 mol% of non-ferroelectric perovskite La(Mg_1/2Ti_1/2)O₃ (BT:2.5% LMT). In addition to the permittivity and P-E hysteresis loop measurements as a function of temperature, local electromechanical properties of BT:2.5% LMT were analysed by piezoresponse force microscopy. It was found that the temperature evolution of the dielectric properties detected by macroscopic methods (average over many grains) is similar to that observed on the nanoscale level (in a single grain). BT:2.5% LMT was revealed to exhibit the typical features of both the ferroelectric and the relaxor. The observed dielectric behaviour is discussed in terms of heterovalent substitution at both A-(Ba²⁺/La³⁺) and B-(Ti⁴⁺/Mg²⁺) perovskite sites.