Raman spectroscopy of (K,Na)NbO3 and (K,Na)1−xLixNbO3

We report Raman spectroscopy in all four phases of a (K0.5+δNa0.5−δ)NbO3 (δ∼0.03) crystal and ((K0.5+δNa0.5−δ)1−xLix)NbO3 for x=0.02 and 0.03. The phase transitions in the Li-free crystal are homogeneous and hysteretic, with no mixed-phase region between the rhombohedral and orthorhombic phases. Raman spectra in the lowest-temperature phase in the Li-doped material differ significantly from those at x=0 and suggest a structural phase boundary at a Li concentration of less than 2%.