Microscopic region effect on the dielectric property of the diffused phase transition ferroelectrics: A reasonable and effective diffuseness characterizing parameter

Based on the microscopic composition fluctuation model and phenomenological theory, a reasonable and effective characterizing parameter of the diffuseness degree of the diffused phase transition (DPT) was defined. The parameter equals to the temperature interval of T∂ε(T)∂T_min= T∂ε(T)∂T_max and which correspond to the temperatures when ∂(T)∂T reaches when the minimum and maximum, respectively. The parameter reflects the diffuseness degree macroscopically and can be easily calculated. This characterizing parameter has been proved to be useful for ferroelectric materials including normal ferroelectrics, common DPT ferroelectrics, and typical relaxor ferroelectrics.