Peculiar properties of phase transitions in Na_0.5 Bi_0.5 TiO₃-0.06BaTiO₃ lead-free relaxor ferroelectrics seen via acoustic emission

Na_0.5Bi_0.5TiO₃-0.06BaTiO₃ relaxor ferroelectrics (RFEs) ceramic samples were investigated by means of dielectric and acoustic emission methods in the temperature range of 70-350C and in dependence on frequency. Dielectric curve exhibits two anomalies: strongly dispersive the local maximum, within 130-180C and slightly dispersive the smeared high-temperature maximum within 300-310C. Acoustic emission exhibits the five groups of bursts: near 123C, 150-180C, near 225C, 300-310C and 327C. The first and third groups of acoustic emission bursts correspond to phase transitions of R3c-P4bm phases coexisting in this temperature, range, while the fourth and fifth groups of acoustic emission bursts correspond to P4bm-P4/mbm-Pm3 m phase transitions. The second group of acoustic emission bursts corresponds to strongly dispersive local maximum at which no phase transition has been proved in Na0.5Bi0.5TiO₃-0.06BaTiO₃. The existence and the location of the intermediate temperature, T∗, in Na0.5Bi0.5TiO₃-0.06BaTiO₃ compound are discussed.