Are the parameters of the empirical law dependent on the dielectric properties of the ferroelectric relaxors?

The empirical law, ɛ = ɛm/[1 + (T − Tm)γ/2σ2] or ɛ = ɛm/{1+[(T − Tm)/Δ]ξ}, are usually used to estimate the degree of the diffused phase transition of the ferroelectric relaxors. As the values of γ or σ (ξ or Δ) are larger, the diffused phase transition is more obvious. However, values of Tm and ɛm are different upon different compositions, dopants, synthesized methods, and others. Are the values of γ and σ (ξ and Δ) affected by Tm or ɛm which represents the characteristics of the relaxors? In this paper, we utilize the experimental data of the (1 − x)Pb(Fe2/3W1/3)O3–xPbTiO3 ceramic system and the mathematical derivation to conclude that the values of γ and σ (ξ and Δ) are not affected by ɛm and Tm. Therefore, they can be used to properly describe and compare the degree of the diffused phase transition between the different samples with different compositions, dopants and synthesized methods since the noises (Tm and ɛm) are filtered in these empirical laws. Furthermore, we can clearly clarify the physical meaning of theses parameters, γ and σ (ξ and Δ), as well as their effect on the composition for the further study.