Lattice dynamics and negative search for pyroelectricity in Sr(1-1.5x)LaxTiO3 ceramics

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 10 K and room temperature. Despite the similarities of the lowfrequency 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 be 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 semiconduting like behaviour at high temperatures was disclosed.