Pressure Measurement at High Temperature Using Ten Sm:YAG Fluorescence Peaks

Abstract

A high-temperature pressure calibration technique using Sm-doped Y₃Al₅O₁₂ (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 cm^–1) at pressures (<i>p</i>) from 1 bar to 19 GPa and temperatures (<i>T</i>) 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 <i>p</i> and <i>T</i>. Several fitting routines for <i>p</i> determination were created based on these dependences, and were tested on various high-<i>p</i> and high-<i>T</i> experimental Sm:YAG fluorescence spectra. The <i>p</i> values obtained from the fitting routines are compared with those obtained from the ruby and the nitrogen (N₂) vibron pressure scales. A fitting routine is proposed that can determine <i>p</i> from 20 to 850 °C within an estimated uncertainty of 0.4 GPa.