Peculiar properties of phase transitions in Na_0.5Bi_0.5TiO₃-xBaTiO₃ (0<x<6) lead-free relaxor ferroelectrics seen via acoustic emission

Na_0.5Bi_0.5TiO₃-xBaTiO₃ (0<x<6) relaxor ferroelectrics crystals were investigated by means of dielectric and acoustic emission methods. Dielectric curves exhibit the slightly visible small maxima near the depolarization temperatures, T_d, and the wide maxima at the temperatures of T_m, whereas the acoustic emission exhibits the sharp bursts, corresponding to T_d, T_lm, which is known to be a temperature exhibiting a strong frequency dispersion, T_RE, which is known to be a temperature above which a frequency dispersion vanishes, and the T_m and the T_p manifesting a transition to the paraelectric phase. Based on the AE data it was established that all these characteristic temperatures shift down as x increases, but with different slopes. A mechanism of such the differences is discussed.