Knowledge Bank

Solid solutions of $K(Tax:Nb1-x)O3$ have been studied by means of far infrared and Raman spectroscopy for $x=0.0,0.25,0.65,0.89$ and 1.0. Members of this series exist in cubic, tetragonal, orthorhombic and rhombohedral phases at successively lower temperatures in the range $10-800\circ K$ except $KTaO3$ which remains cubic. In the paraelectric (cubic) phase these materials exhibit a strong infrared reflectance spectrum and a second order Raman spectrum similar to $KTaO3$. The infrared spectra are relatively unaffected through the various ferroelectric phase transitions but the Raman spectra exhibit strong first order bands which alter markedly at each structural change. Considerable hysteresis is observed in the spectra at most transitions. The infrared measurements provided a starting point for the interpretation of the Raman spectra and assignments of the phonon modes in each phase as a function of composition will be reported.