Diffuse Phase Transition of Potassium Lithium Niobate Single Crystals Probed by Brillouin Scattering

A Brillouin light scattering study has been carried out on tungsten-bronze K5.80Li3.82Nb10.12O30 (KLN-1) single crystals, which exhibited diffuse ferroelectric phase transitions at Tc 700 K. Polarized central peaks (CPs) were observed in the paraelectric phase, indicating the existence of precursor polar clusters. The relaxation time, estimated from the width of the CP, showed a substantial increase at T Tc + 100 K, at which the polar clusters seemed to become more correlated and longer lived than at higher temperatures, similar to the case of the most typical uniaxial relaxor, (Sr0.61Ba0.39)5Nb10O30 (SBN-61). The temperature dependence of the relaxation time showed a different behavior from that of the typical order-disorder-type ferroelectrics, which has been ascribed to the intrinsic disorder of the unfilled tungsten-bronze structure and the resulting quenched random electric fields. KCI Citation Count: 4