Li doping effect on properties and phase transfomations of KNbO3

Dielectric permittivity and infrared reflectivity spectra of Li doped KNbO3 single crystals have been studied for the first time for K1−xLixNbO3 with x = 0.015, 0.02, 0.065. It was found that Li admixture results in occurrence of dielectric relaxation with the relaxation parameters very close to those in Li doped KTaO3. The relaxation was attributed to π/2 dipole reorientation of Li+ 〈1 0 0〉 off-centers substituted for K+, which appear to be present in both paraelectric cubic phase and in ferroelectric phase down to low-temperatures. Besides, Li doping is accompanied by an increase of the cubic-tetragonal phase transition temperature, a decrease of tetragonal-orthorhombic-rhombohedral phase transition temperatures and TO soft mode stiffening at room temperature.