Piezoelectric (Na0.5K0.5)NbO3-SrTiO3 Ceramics in the Tetragonal-Orthorhombic Phase Boundary Studied by Raman Spectroscopy.

Raman spectroscopy of lead-free piezoelectric (1-x)(Na0.5K0.5)NbO3-xSrTiO3 ceramics and (Na1 - yKy)NbO3 ones sintered by the Spark-Plasma-Sintering method have been performed to investigate the dynamical property in the intermediate phase of x = 0.05. From the comparison of Raman spectra between (1-x)(Na0.5K0.5)NbO3-xSrTiO3 and (Na1 - yKy)NbO3 at room temperature, the overdamped mode which became soften was found in the intermediate phase at x = 0.05. Although it is difficult to assign the mode because of using ceramics samples, this result has a possibility that the overdamped mode includes the soft mode observed in the orthorhombic phase. [ABSTRACT FROM AUTHOR]