Temperature shift of the Fe2+ absorption band in LiNbO3:Fe crystal

Abstract

The temperature dependence of the Fe2+ absorption band of a strongly oxidized LiNbO3: Fe crystal is reported over the range from 25 to 350 degreesC, where the effect of temperature on the band is reversible. The band broadens and shifts to lower energy as temperature is increased. The rate at which the absorption peak energy decreases with increasing temperature is calculated as -6.8 x 10(-5) eV/degreesC from the slope of the straight-line fit to the temperature against peak position energy graph. We propose that the origin of the temperature shift is due to both a shift of the energetic position of impurities and the decrease of the band gap energy. The consistency between the calculated rate by the help of a simplified model which describes the shift of the band gap energy in the frame of the lattice dilation and the observed rate suggests that the lattice dilation might be responsible for the temperature shift of the band.