Diffuseness as a Useful Parameter for Relaxor Ceramics

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Abstract
The low‐field electrical behavior of relaxor ferroelectric ceramics has been qualitatively described by many parameters, including diffuseness (δ), which characterizes the breadth of the transition peak and is roughly related to the standard deviation of the peak. Three major types of equations have been used to calculate δ: Gaussian distribution (originated by Smolenskii and Rolov et al.), power law (used by many authors), and variable power law (Uchino et al). In this work, the three calculational techniques are compared analytically and illustrated using dielectric data from ceramic 0.88Pb(Mg1/3Nb2/3)O3. 0.12PbTiO3. All three methods of analysis result in very linear plots; however, the calculated values of δ are significantly different. A method of limiting the temperature range to that corresponding to 2/3 of the maximum relative dielectric constant is suggested in order to decrease the deviations. This limitation is shown to give consistent reproducible diffuseness values without extraneous contributions arising from the relaxor nature of the material or from differing temperature ranges of measurement, thus allowing δ to be used as an effective comparative parameter for relaxor ceramics.