Pressure measurement at high temperature using ten Sm:YAG fluorescence peaks

Abstract

A high-temperature pressure calibration technique using Sm-doped Y 3 Al 5 O 12 ͑Sm:YAG͒ crystal as the pressure calibrant has been developed by studying its Y1 through Y10 fluorescence peaks ͑frequencies from 15 600 to 17 200 cm Ϫ1 ͒ at pressures ͑p͒ from 1 bar to 19 GPa and temperatures ͑T͒ from 20 to 850°C in externally heated diamond anvil cells. The entire spectrum was fit to a sum of ten Lorentzians plus a linear background. The positions, relative intensities and widths were represented by empirical functions of p and T. Several fitting routines for p determination were created based on these dependences, and were tested on various high-p and high-T experimental Sm:YAG fluorescence spectra. The p values obtained from the fitting routines are compared with those obtained from the ruby and the nitrogen (N 2) vibron pressure scales. A fitting routine is proposed that can determine p from 20 to 850°C within an estimated uncertainty of 0.4 GPa.

The Sm:YAG primary fluorescence pressure scale

“…This implies that pressures determined using Sm:YAG in similar pressure media, where similar levels of deviatoric stress are developed, should be more comparable than those measured using the ruby scale. Since the Sm:YAG Y‐fluorescence bands have been reported to have a negligible temperature dependence [ Hess and Schiferl , ; Zhao et al ., ; Goncharov et al ., ], Sm:YAG is a potentially superior material for measuring pressures at elevated temperatures. Previous studies [ Wei et al ., ; Goncharov et al ., ], where experiments at simultaneous high pressure and temperature were performed, demonstrate that Sm:YAG can be implemented as a pressure gauge to approximately 100 GPa and temperatures of approximately 800 K. Moreover, chemical contamination of Sm:YAG to the samples was not observed in these last references.…”

“…The structure of Sm:YAG consists of a three‐dimensional corner‐sharing network of AlO 6 octahedra (Al in 16 (a) sites and O in 96 (h) sites) and AlO 4 tetrahedra (Al in 24 (d) sites) that form interstitial Y/Sm sites (24c) which are eightfold coordination with oxygen. Sm:YAG exhibits several pressure‐dependent fluorescence bands [ Hess and Schiferl , ; Zhao et al ., ] with wavelengths that do not depend on Sm content [ Sanchez‐Valle et al ., ]. The necessity for a primary pressure calibration is clearly demonstrated by the fact that previous pressure calibrations for the major fluorescence band of Sm:YAG, which have been performed using secondary pressure standards, predict pressures at ~20 GPa that vary by ~25% (supporting information Figures S1 and S2).…”

Pressure and Stress Effects on Diffusion in Si

“…However, above around 200 °C the ruby signal becomes so faint and broad that it is virtually impossible to use. Fluorescence from Sm-doped YAG is still going strong as high as 850 °C, however, and we have now calibrated ten fluorescence peaks vs. T and p up to 850 °C and 19 GPa [18]. It turns out that we need all ten peaks in order to get a reliable pressure measurement at high T. Fitting ten fluorescence peaks which are fairly broad at high T is not trivial, and therefore we will be distributing the necessary tools via the World-Wide Web so that others can readily use Sm:YAG for pressure measurement at high T.…”

Optical calibration of pressure sensors for high pressures and temperatures

“…the dopant in Al 2 O 3 that produces ruby). For example, the Y band of Sm:YAG has been found attractive because its frequency shift with temperature is negligible up to 820 K and that with pressure is comparable to ruby (0.3360 nm/GPa) [6,7]. However, this Y band is composed of many peaks, which, like ruby, strongly overlap at high pressure and/or high temperature.…”