Pressure-induced effects on the spectroscopic properties of Nd³⁺ in MgO:LiNbO₃ single crystal. A crystal field approach

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• 作者：J.E. Muñ ; oz Santiuste^a ; ^b ; ^{jems@fis.uc3m.es} ; V. Laví ; n^b ; ^c ; U.R. Rodrí ; guez-Mendoza^b ; ^c ; M.M. Tardio^a ; R. Ramí ; rez-Jimé ; nez^a
• 关键词：High pressure ; Lithium niobate ; Rare earth ions ; Nd ; Photoluminescence ; Energy levels ; Crystal-field
• 刊名：Journal of Luminescence
• 出版年：2017
• 出版时间：April 2017
• 年：2017
• 卷：184
• 期：Complete
• 页码：293-303
• 全文大小：1356 K
• 卷排序：184

文摘

The effects of pressure on the Nd3+-doped MgO:LiNbO3 single crystal have been studied by luminescence spectroscopy at low temperature and high pressures from ambient conditions up to 33 GPa. Specifically, the pressure-induced evolution of the emission spectra, corresponding to the 4F3/2→4I9/2,4I11/2 transitions, and the excitation spectra, corresponding to the 4I9/2→4F5/2+2H9/2, and 4I9/2→4F7/2+4S3/2 transitions, show a gradual red-shift that follows a linear pressure dependence and a decrease in the intensity of the spectra with increasing pressure. The initial effect of increasing pressure on the MgO:LiNbO3 crystal is the modification of the relative amount of the several centers in the sample. At pressures around 20 GPa the characteristic multicenter Nd3+ structure eventually disappears indicating that all the centers have very similar environments near this pressure. At higher pressures, observed changes seem to have a different origin. The evolution of Nd3+ luminescence is studied in the frame of crystal-field theory in order to evaluate its capability of monitoring the pressure-induced structural changes. Crystal-field analysis, under approximated C3v symmetry, shows a smooth increase of the overall crystal-field strength on the luminescent ion, which can be related to the volume reduction as pressure increases. Crystal-field parameters also show a general monotonic behavior with pressure that indicates a structural modification of the local structure that, maintaining the trigonal symmetry around the impurity ion, evolves towards a lower axial character. No evidences of a phase transition have been observed in the studied pressure range.