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

A high-temperature pressure calibration technique using Sm-doped ${\mathrm{Y}}_{\mathrm{3}}{\mathrm{Al}}_{\mathrm{5}}{\mathrm{O}}_{12}$ (Sm:YAG) crystal as the pressure calibrant has been developed by studying its Y1 through Y10 fluorescence peaks (frequencies from 15 600 to 17 200 ${\mathrm{cm}}^{\text{−1}})$ at pressures (p) from 1 bar to 19 GPa and temperatures (T) 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 $({\mathrm{N}}_2)$ vibron pressure scales. A fitting routine is proposed that can determine p from 20 to $\text{850\hspace{0.17em}°}\mathrm{C}$ within an estimated uncertainty of 0.4 GPa.