Characteristic temperatures and field effect in KTa _1-xNb _xO ₃ relaxor crystals seen via acoustic emission

[100]-oriented KTa _1-xNb _xO ₃ (x=0.32) relaxor ferroelectric crystals have been studied by acoustic emission (AE) count rate in the temperature range from 200 K to 700 K. Burns temperature T _d=620 K (N = 1.7 ^-1) and intermediate temperature T ^*=310 K ( = 3.1 ^-1) as well as both the tetragonal-cubic T _T-C=259 K (N = 4.0 ^-1) and orthorhombic-tetragonal T _O-T=243 K (N = 5.0 ^-1) phase transition temperatures have been clearly detected. T ^* is found to be influenced by an external DC electric field E:T ^* essentially decreases with a slope of approximately - 60 Kcm/kV accompanied with weakening in , as E enhances. The mechanisms of abnormal T ^*(E) and (T) dependences are discussed.