Phenomenological description of dielectric permittivity peak in relaxor ferroelectrics

Lead-free barium zirconate-titanate/barium calcium-titanate, [(BaZr0.2Ti0.80)O3]1?x?[(Ba0.70Ca0.30)TiO3]x (x = 0.10, 0.15, 0.20) (BZT?BCT) ceramics with high dielectric constant, low dielectric loss and moderate electric breakdown field were prepared by the sol?gel synthesis technique. X-ray diffraction patterns revealed tetragonal crystal structure and this was further confirmed by Raman spectra. Well-behaved ferroelectric hysteresis loops and moderate polarizations (spontaneous polarization, Ps ~ 3?6??C?cm?2) were obtained in these BZT?BCT ceramics. Frequency-dependent dielectric spectra confirmed that ferroelectric diffuse phase transition (DPT) exists near room temperature. Scanning electron microscope images revealed monolithic grain growth in samples sintered at 1280??C. 1000/? versus (T) plots revealed ferroelectric DPT behaviour with estimated ? values of ~1.52, 1.51 and 1.88, respectively, for the studied BZT?BCT compositions. All three compositions showed packing-limited breakdown fields of ~47?73?kV?cm?1 with an energy density of 0.05?0.6?J?cm?3 for thick ceramics (>1?mm). Therefore these compositions might be useful in Y5V-type capacitor applications.

https://iopscience.iop.org/article/10.1088/0022-3727/44/39/395403/pdf

Barium zirconate-titanate/barium calcium-titanate ceramics via sol?gel process: novel high-energy-density capacitors

Structure, dielectric tunability, thermal stability and diffuse phase transition behavior of lead free BZT-BCT ceramic capacitors

Ba0.9Ca0.1TiO3 ceramics have been fabricated using powders obtained by calcining mixtures of (i) BaCO3, CaCO3 and TiO2 and (ii) Ba0.9Ca0.1CO3 and TiO2. The precursor Ba0.9Ca0.1CO3 was prepared by a wet technique to ensure homogeneous mixing of Ba and Ca ions at the atomic level. DTA analysis of solid state thermochemical reactions in the two types of mixtures shows that the temperature of reaction completion is 140 degrees C lower for the mixture containing the precursor carbonate solid solution. XRD results indicate better chemical homogeneity for powders obtained by the new route. A powder diffraction pattern for Ba0.9Ca0.1TiO3 has been theoretically computed assuming partial substitution of Ba2+ by Ca2+. The theoretically predicted intensities are in good agreement with those experimentally observed for powders prepared by the precursor route only. Better chemical homogeneity with respect to the distribution of Ca2+ ions leads to more pronounced diffuse phase transition in Ba0.9Ca0.1TiO3 ceramics.

The influence of a powder processing technique on chemical homogeneity and the diffuse phase transition behaviour of Ba0.9Ca0.1TiO3 ceramics

https://ris.utwente.nl/ws/files/6881566/Keizer78anomalous.pdf

Anomalous dielectric behaviour of La(III) substituted lead titanate ceramics

https://ris.utwente.nl/ws/files/6738453/Wolters75relax.pdf

A.J. Burggraaf

Papers

Relaxational polarization and diffuse phase transitions of LA-substituted Pb (Zr,Ti)O3-ceramics