Title: Effect of pressure on site-symmetry distortions of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msup><mml:mrow><mml:mi mathvariant="normal">Mn</mml:mi></mml:mrow><mml:mrow><mml:mn>5</mml:mn><mml:mo>+</mml:mo></mml:mrow></mml:msup></mml:mrow></mml:math>and<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msup><mml:mrow><mml:mi mathvariant="normal">Cr</mml:mi></mml:mrow><mml:mrow><mml:mn>4</mml:mn><mml:mo>+</mml:mo…
Abstract: High pressure is used to study the effects of nontetrahedral site distortions on luminescence properties of ${\mathrm{Cr}}^{4+}$ and ${\mathrm{Mn}}^{5+}$ in ${\mathrm{Y}}_{2}{\mathrm{SiO}}_{5}.$ Luminescence spectra and lifetime measurements of ${\mathrm{Mn}}^{5+}:{\mathrm{Y}}_{2}{\mathrm{SiO}}_{5}$ as a function of pressure up to 120 kbar indicated that the local ${\mathrm{Mn}}^{5+}$ site distortion increased strongly up to $\ensuremath{\sim}50$ kbar and increased only slightly at higher pressure. A crystal field energy level calculation that included spin-orbit coupling effects was completed to quantitatively model the luminescence and lifetime data in the context of a ${D}_{2d}$ distortion model. The model provided excellent agreement with the spectral and lifetime data and showed that the ${}^{3}{T}_{1}$ state has a significant influence on the lifetime of ${}^{1}E$ luminescence. Luminescence studies of ${\mathrm{Cr}}^{4+}:{\mathrm{Y}}_{2}{\mathrm{SiO}}_{5}$ revealed a redshift up to $\ensuremath{\sim}40$ kbar followed by a blue shift at higher pressure. These results are consistent with a pronounced increase in the ${\mathrm{Cr}}^{4+}$ site distortion up to $\ensuremath{\sim}40$ kbar that levels off at higher pressures. The ${\mathrm{Cr}}^{4+}:{\mathrm{Y}}_{2}{\mathrm{SiO}}_{5}$ results also support assignment of the ambient-pressure luminescence spectrum to a transition from orbital components of the ${}^{3}{T}_{2}$ state to the ${}^{3}{A}_{2}$ ground state. No evidence of a ${}^{3}{T}_{2}{\ensuremath{-}}^{1}E$ electronic crossover in ${\mathrm{Cr}}^{4+}:{\mathrm{Y}}_{2}{\mathrm{SiO}}_{5}$ was observed up to 120 kbar. The results indicate more generally that the luminescence properties of ${3d}^{2}$ systems are controlled by competing cubic crystal field and distortion effects. The ability of modest pressures to alter the relative importance of these effects suggests that cubic crystal field and distortions vary widely from host lattice to host lattice at ambient pressure and are responsible for the complicated optical properties of ${3d}^{2}$ ions.
Publication Year: 2000
Publication Date: 2000-04-01
Language: en
Type: article
Indexed In: ['crossref']
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Cited By Count: 8
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