Crystal optical studies of spontaneous and precursor polarization inKNbO3

Thermal expansion properties of PMN–PT ceramics

“…T d , so-called the Burn temperature, is the temperature where randomly oriented polar nanoregions become detectable within the otherwise non-polar paraelectric phase of several ferroelectrics. Originally observed in BaTiO 3 due to the characteristic anomaly of the refractive index [3], polar precursor clusters were later on detected in PbTiO 3 [4], KNbO 3 [5] and in the relaxor ferroelectrics PLZT [6], PMN, PZN [7] and SBN [8]. The polar regions are formed in the course of cooling at a temperature T d ≈ 350 • C, which is considerably higher than the temperature T m (T m ≈ −10 • C for PMN).…”

Electrocaloric response of KNbO3 from a first-principles effective Hamiltonian

“…Ge et al [25] studied the impact of crystal size on the polarization in KNbO 3 and found a spontaneous polarization of 40.3 C cm −2 . Kleemann et al [26] reported a spontaneous polarization of 37 C cm −2 . The variation in these values is due to difference in the samples, 1 The feram software is distributed freely under the GNU general public license at http://loto.sourceforge.net/feram/.…”

Phase transitions in Sr 0.61 Ba 0.39 Nb 2 O 6 :Ce 3+ : II. Linear birefringence studies of spontaneous and precursor polarization

“…Note that P = P z withẑ c. n 0 denotes the average high-temperature refractive index. In the paraelectric regime, at T > T c , the autocorrelation function P 2 ≡ δP 2 is connected with the q-dependent susceptibility χ(q) via the fluctuation-dissipation theorem [25] …”