Photoluminescence study of LiNbO3:Cr3+; W4+ at high pressure. Pressure dependence of spectroscopic parameters and local structure of Cr3+

In this study, the photoluminescence properties of congruent codoped LiNbO3:Cr3+; W4+, crystals have been systematically investigated by performing photoluminescence studies at room temperature in the 0-280 kbar pressure range. In particular, we focus on the influence that hydrostatic pressure has on the 2E→ 4A2 (R-lines) transitions of Cr3+. It has been observed that the pressure dependence of the spectral position of the R-lines associated with both Cr3+ centres β and γ shows a bilinear behaviour with an abrupt slope change near 210 kbar. This change is related to the existence of a pressure-induced structural phase transition in the LiNbO3 host. The analysis of experimental results provides the Racah parameters B and C and the crystal field parameter 10Dq and their pressure and volume, through the crystal field theory and equation of state, dependences.