- JOURNAL OF LUMINESCENCE Journal
- April 2017
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- 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 F-4(3/2)-> I-4(9/2),(4),I-11/2 transitions, and the excitation spectra, corresponding to the I-4(9/2)-> F-4(5/2)+H-2(9/2), and I-4(9/2)-> F-4(7/2)+S-4(3/2) 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 C-3v symmbtry, 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. (C) 2016 Elsevier B.V. All rights reserved.
- high pressure; lithium niobate; rare earth ions; nd; photoluminescence; energy levels; crystal-field; simple overlap model; rare-earth ions; ferroelectric lithium-niobate; 24 degrees-c; laser oscillation; linbo3 crystal; sites; nd-mgo-linbo3; simulations; diffraction