  Dielectric permittivity and infrared reflectivity spectra of Li doped KNbO3
single crystals have been studied for the first time for K1-xLixNbO3 (KLN) with
x = 0.015, 0.02, 0.065. It was found that like in KTaO3, Li admixture results
in appearance of dielectric relaxation with the relaxation parameters very
close to those in KTaO3 quantum paraelectric. It was attributed to 90-grad
dipole reorientation of Li+ <100> off centers substituted K+, which appear to
be presents as in paraelectric cubic phase as in ferroelectric phase down to
low temperatures. Besides, Li doping is accompanied by increasing of the
cubic-tetragonal phase transition point, decreasing of
tetragonal-orthorhombic-rhombohedral phase transition points and TO soft mode
stiffen at room temperature.
