Diffuseness as a Useful Parameter for Relaxor Ceramics

Abstract

The low-field electrical behavior of relaxor ferroelectric ceramics has been qualitatively described by many parameters, including diffuseness (6), 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 6: Gaussian distribution (originated by Smolenskii and Rolov et d.), 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(Mg1,3Nbzi3)03. 0.12PbTi03. All three methods of analysis result in very linear plots; however, the calculated values of S are significantly different. A method of limitingthe 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 6 to be used as an effective comparative parameter for relaxor ceramics. [

Microstructure and electrical properties of Aurivillius phase (CaBi2Nb2O9)1−x(BaBi2Nb2O9)x solid solution

“…A modified CurieWeiss law −1 − m −1 = ͑T − T m ͒ ␥ / C 2 ͑T m is the temperature of the maximum permittivity m at a given frequency, ␥ = 1 for normal ferroelectrics and ␥ = 2 for ideal relaxor͒ is often used to fit the permittivity data. 39 The ␥ values obtained at 1 MHz are close to 2, confirming the relaxor nature of these compositions ͑Table III͒. The Curie constants C 2 for x Ն 0.8 are one or two orders of magnitude higher than the C 1 values for the compositions with x = 0 -0.5, which is consistent with the previous studies on relaxor behavior in BLSFs compounds.…”

Dielectric and electrical properties of Na2Pb2La2W2Ti4Ta4O30 electroceramics

“…4), which supports higher degree of disordering in the system [32]. The diffused phase transition in TB compounds may be considered due to randomness of atoms distribution and in-homogeneity.…”

Enhanced dielectric and ferroelectric characteristics in Ca-modified BaTiO3 ceramics

“…2) are obtained by Ca-substitution, and this also contributes to the increased room temperature dielectric properties. The modified Curie-Weiss relation 22 is used to evaluate the diffuse degree of the C-T transition:…”