Calibration of berlinite (AlPO _4) as Raman spectroscopic pressure sensor for diamond-anvil cell experiments at elevated temperatures

摘要

Changes in the band position of the 462 and the 1111 cm ~(-1) A _1 modes of berlinite (AlPO _4) with temperature and pressure were determined in situ to 500°C and to 10 GPa using Raman spectroscopy and diamond-anvil cells. These bands shift in opposite directions with pressure and, likewise, with temperature. At a known temperature, the relative difference of both band positions (Δν) _(P,T) can therefore be used as a pressure gauge that does not require calibration of the spectrometer. At ambient pressure, the observed temperature dependence of this relative difference of the line positions is very close to linear and can be described by (Δν) _(T, 0.1 MPa) (cm ~(-1)) = 0.0181 T - 0.46 where 23 ≤T (°C)≤500. Along the 23°C isotherm to 10 GPa, pressure and relative wavenumber difference (Δν) _(P, 23°C) are related by the equation P (GPa) = 0.00083 [(Δν) _(P, 23°C)] ~2 - 0.062 (Δν) _(P, 23°C). Both equations can be combined to determine pressures at higher temperatures under the assumption that the change in (Δν) _(P,T) with pressure is insensitive to temperature.