A Raman and dielectric study of ferroelectric ceramics

Abstract

Dielectric and Raman scattering experiments were performed on various ceramics with composition Ba(Ti1−xZrx)O3. Such lead-free, environmental-friendly materials were shown, from dielectric measurements, to exhibit behaviours extending from conventional to relaxor ferroelectrics on increasing the zirconium concentration. The evolution of the Raman spectra was studied as a function of temperature for various compositions, and the spectroscopic signature of the corresponding phases was determined. In the relaxor state, the variation of the integrated intensity of the Raman lines with temperature showed a plateau at low temperature. This anomaly was also detected as a peak in depolarization current measurements, and attributed to ergodicity breaking which characterizes usual relaxor systems. Raman results hint at locally rhombohedral polar nanoregions resulting from the random fields associated with Zr ions.

Electrocaloric effects in the lead-free Ba(Zr,Ti)O3 relaxor ferroelectric from atomistic simulations

“…They also display several characteristic temperatures (i.e., the T b Burns temperature, the T * temperature and the T m temperature) that are associated with a subtle change in some physical properties [29][30][31][32][33][34]. For instance, in Ba(Zr 0.5 Ti 0.5 )O 3 (BZT) relaxor ferroelectrics, simulations [35] indicate that the Burns temperature (below which the dielectric response does not obey the Curie-Weiss law [36]) is T b ≃ 450 K , T * ≃ 240 K, and T m ≃ 130 K is the temperature at which the dielectric response exhibits a peak, as also in-line with measurements in BZT compounds [33,34,37,38]. The microscopic origin of these features is commonly believed to be the existence of the so-called polar nanoregions (PNRs) below the Burns temperature [39].…”

“…Since we are also interested in checking if and how this difference (if any) depends on the investigated temperature region, we decided to focus on four particular representative temperatures. They are: (1) 500 K, which is above the predicted Burns temperature (T b ≃ 450 K) of BZT [35,37]; (2) 300 K, which is located in-between our critical T * ≃ 240 K [33][34][35] and T b ; (3) 200 K, that is now between the computed T m temperature of BZT (T m ≃ 130 K) [35,38] and T * ; and (4) 100 K, which is thus below T m (note that the Supplemental Material [54] also shows our results for the EC coefficient in BZT at 600 K). Figure 2 shows the electrocaloric coefficient as a function of electric field, E, for these four different selected temperatures, and as computed from the aforementioned MC-1, MC-2 and MD methods.…”

EXAFS study of lead-free relaxor ferroelectricBaTi1−xZrxO3at the ZrLaulhé1, Hippert2, Kreisel3 et al. 2006Phys. Rev. BSelf Cite1042651View full textAdd to dashboardCite

“…Yet it is not known how, and on which scale such random elastic fields build up. The BaTi 1−x Zr x O 3 solid solution thus opens an interesting route towards the comprehension of the relaxor behavior, and raises much interest 7,22,23,24,25,26 . Furthermore, it is intriguing that PbZr 1−x Ti x O 3 (PZT) shows no relaxation 27 while BTZ does.…”

Glassy behavior study of dysprosium doped barium zirconium titanate relaxor ferroelectric

“…For higher zirconium concentrations (x > 0.15) only a rhombohedral-to-cubic phase transition is observed. Furthermore, the phase transition of this system changes from a "normal" ferroelectric to a typical relaxor behavior by increasing zirconium concentration (until x = 0.75) [16][17][18][19][20][21] which is caused by the inhomogeneous distribution of [ZrO 6 ] clusters into the titanium (Ti) sites and/or by the mechanical stresses on the grains [19]. A polar cluster like behavior is obtained for Zr-rich BZT compositions (x > 0.75) [17].…”