Phase‐transition studies of Ba_0.90Ca_0.10(Ti_1−xZr_x)O₃ ferroelectric ceramic compounds

Abstract

Phone: þ55 16 3373 9828, Fax: þ55 16 3373 9824Perovskite-structured Ba 0.90 Ca 0.10 (Ti 1Àx Zr x )O 3 ceramics were prepared in this work and subsequently studied in terms of composition-dependent dielectric and high-resolution longrange order structural properties from 30 to 450 K. The dielectric response of these materials was measured at several frequencies in the range from 1 kHz to 1 MHz. Combining both techniques, including Rietveld refinement of the X-ray diffraction data, allowed observing that, when increasing Zr 4þ content, the materials change from conventional to diffuse and relaxor ferroelectric compounds, the transition occurring spontaneously at the x ¼ 0.18 composition. Interestingly, this spontaneous transition turned out to be prevented for a further increase of Zr 4þ . On the basis of all the dielectric and structural results processed, a phase diagram of this system is presented.

Local structure and hybridization states in Ba0.9Ca0.1Ti1−Zr O3 ceramic compounds: Correlation with a normal or relaxor ferroelectric character

“…The decrease in the intensity of the FT peaks can be interpreted in terms of either a decrease in the number of Ba neighbors or an increase in the Debye-Waller factor value. According to previous XRD studies [30], these samples exhibit a cubic symmetry at room temperature. Therefore, at least for the Ba-O first coordination shell, no variation in the number of neighbors is expected.…”

“…Ba 0,9 Ca 0,1 Ti 1Àx Zr x O 3 ceramic samples, hereafter labeled BCZT100 * x (where x = 0.00, 0.05, 0.09, 0.18, 0.20, 0.22, 0.24 and 0.27), were prepared by the solid-state reaction method. A detailed description of the sample preparation can be found elsewhere [30].…”

“…The amplitude and phase shift data were calculated using the FEFF8 theoretical ab initio code with the input files issued from MAX-Crystalffrev [29,32]. The MAX-Crystalffrev code enables substitutions and vacancies in the input crystal structure obtained from Rietveld refinements [30]. EXAFS data fitting used the standard EXAFS formula according to the reports of the IXS standard and criteria subcommittees [33].…”

Enhanced temperature stability and quality factor with Hf substitution for Sn and MnO2 doping of (Ba0.97Ca0.03)(Ti0.96Sn0.04)O3 lead-free piezoelectric ceramics with high Curie temperature

“…At the same time, the Curie temperature (T C ) obviously shifts to room temperature. 11,12 Wang et al reported that when substituting Ca 2+ for Ba 2+ at the A-site in BT ceramics, T R-O and T O-T decrease. At the same time, T C does not obviously change owing to the enhancement of atomic polarizability and the shrinkage of the unit cell volume having opposing effects.…”

Local order of Pb1−xLaxZr0.40Ti0.60O3 ferroelectric ceramic materials probed by X-ray absorption and Raman spectroscopies

“…In lead-and barium-based perovskite ferroelectric relaxor materials, above and below the temperature of maximum of dielectric permittivity (T m ), the X-ray diffraction (XRD) technique shows the existence of a long-range order cubic symmetry with no phase transition [11,12]. However, the observation of a cubic symmetry is not compatible with the observation of a relaxor state in these samples.…”