Relaxation processes in the region of structural phase transitions on the example of ceramics based on sodium niobate

Abstract

Comparative studies of the temperature dependences and dispersion of the complex permittivity of sodium niobate and sodium-lithium niobate ceramics have been carried out. It is shown that the structural transition to the R-phase (370oC) of sodium niobate ceramics is a ferroelectric phase transition. For sodium niobate ceramics, the existence of three fundamentally different mechanisms of relaxation processes has been established: classical (Debye type), linear, and relaxation, the existence of which is determined by the structural phase. The addition of 10% lithium niobate to the sodium niobate ceramics not only increases the temperature of the structural phase transition, but also eliminates the mechanisms for the occurrence of relaxation polarization. Keywords: piezoelectric ceramics, lead-free materials, permittivity, relaxation processes.