Sr 0.75Ba 0.25Nb 2O 6 -oriented uniaxial tungsten bronze relaxor crystals have been studied by means of dedicated acoustic emission during their thermal cycling in 150-300 K temperature range under dc electric field (E). A 1 st order transition in a modulated incommensurate tetragonal phase has been successfully detected at T m i 198 K on heating and T m i 184 K on cooling, respectively. As field E enhances, a thermal hysteresis gradually narrows and vanishes in the critical point at E th 0.31 kV/cm, above which a phase transition becomes to 2 nd order. The T m i(E) dependence looks as a V-shape dip, not similar that previously has been looked as a smeared minimum between both the two polar and nonpolar tetragonal phases near T m 220÷230 K in the same crystals (Dul'kin, J Appl. Phys. 110, 044106 (2011)). Due to such a V-shape dip is characteristic for Pb-based multiaxial perovskite relaxor, a rhombohedral phase is waited to be induced by a field E in the critical point temperature range. The emergence of this rhombohedral phase as a crucial evidence of an orthorhombic phase presumably existing within the modulated incommensurate tetragonal phase in tungsten bronze Sr xBa 1-xNb 2O 6 relaxor is discussed.
All Science Journal Classification (ASJC) codes
- Physics and Astronomy(all)