The various phases of the system Sr1-xCaxTiO3—A Raman scattering study

Abstract

This paper deals with the structural Raman-active and the disorder-induced TO and LO Raman modes in Sr 1−x Ca x TiO 3 (SCT) ceramics. Spectra were recorded at ambient pressure in a wide range of temperatures from 8 K up to ≈500 K. The chemical composition (x) was chosen so as to investigate the phase boundaries which have been previously determined in the x-T phase diagram. An eigenvector analysis is given for all the known phases. The Raman data confirm the occurrence of a double-tilt system of Imma space group lying between the tetragonal I4/mcm and the orthorhombic Pbnm structures for x ½ 0.06. Higher-order transformation of the antiferroelectric phase (0.20 Ä x Ä 0.40) at low temperature is also suggested. The main interesting disorder-induced effects originate from the temperature behaviour of the hard polar modes TO 2 and TO 4 , which appear in the Raman spectra of the paraelectric domain. This behaviour allows one to discuss the precursor range of ferroelectricity in the SCT system in terms of ferroelectric-or antiferroelectric-type dipolar interactions.

Structural, microwave dielectric properties and dielectric resonator antenna studies of Sr(ZrxTi1−x)O3 ceramics

“…When transition takes place from cubic to tetragonal, Raman inactive F 1u softmode of cubic phase becomes the 1st order Raman scattering of A 1g and E g modes and the so called silent mode F 2u transforms to the E g + B 1g mode [54] and along with that B 2g mode is also observed. With 10% adding of Zr content on B-site of SrTiO 3 , three basic modes B 1g , B 2g and E g which are the signature of tetragonal phase [49,55,56] are observed near 240 cm −1 , 454 cm −1 and 505 cm −1 respectively (see Table 2). This confirms the existence of tetragonal phase in x = 0.1 composition.…”

Elastic and anelastic anomalies in (Ca,Sr)TiO3 perovskites: Analogue behaviour for silicate perovskites

“…A recently proposed phase diagram is reproduced in Figure 1, after Carpenter et al (2006a). For Ca-rich compositions, the sequence of transitions with falling temperature is Pandey, 1999, 2001a;Ranjan et al, 2000;Mishra et al, 2001;Ouillon et al, 2002;Ranson et al, 2005;Mishra et al, 2005Mishra et al, , 2006a, and there has been a further suggestion of monoclinic symmetry (Woodward et al, 2006). From an earth sciences perspective, the CST solid solution has…”

The magnetic transition temperature tuned by strain in YMn0.9Ru0.1O3 thin films

“…[22][23][24] of TO 1 or TA mode is observed at 620 cm -1 , which is assigned to the second-order mode. [25][26][27] The B 2g (1) mode of orthorhombic YMnO 3 is also at this position. 28 Thus, the peak at 620 cm -1 includes the TO 4 mode of STO substrate and B 2g (1) mode of YMRO film.…”