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Novel lead-free piezoelectric single-crystal with a morphotropic boundary composition (0.94Na1/2Bi1/2TiO3-0.06BaTiO3) was characterized by dielectric spectroscopy, far-IR reflectivity and Raman spectroscopy. Analysis of polarized Raman spectra suggests that the three principal Raman bands are associated with polar optic modes. [ABSTRACT FROM AUTHOR]

Lattice dynamics and polar properties in lanthanum doped SrTiO3 (STO) ceramics, with general formulae Sr(1-1.5x)LaxTiO3 were studied in the temperature range between to K and room temperature. Despite the similarities of the low frequency Raman spectra, for differently (x = 0.0533, 0.080 and 0.133) La-doped ceramics, and the spectra of the undoped ceramics, the TO1 polar soft mode could not he detected in those systems, which confirms the non-existence of a ferroelectric phase at low temperatures. Raman spectra analysis provides evidence for drastic effects determined by La3+ impurity in the critical temperature shift of the para-antiferrodistortive phase transition of STO, accompanied with a continuing change of the lattice dynamics by increasing lanthanum concentration. The absence of a pyroelectric current confirms the non-existence of a polar character in the low temperature range. The existence of semiconducting like behaviour at high temperatures was disclosed. [ABSTRACT FROM AUTHOR]

Luminescence of Crk3+ centres in Sr1-xCaxTiO3 (x = 0-0.12) reveals an unusual "dielectric related" temperature shift of the R lines, which correlates well with reciprocal dielectric permittivity behaviour and depends on the character of the phase transitions. The position of the R lines shifts to higher energies with Ca addition. Results obtained are attributed to interaction of the impurity centres with the soft TO1 branch, structural changes and random fields, which are inherent in Sr1-xCaxTiO3. [ABSTRACT FROM AUTHOR]