Improved calibration of the SrB4O7:Sm2+ optical pressure gauge: Advantages at very high pressures and high temperatures

This paper presents a new calibration of the pressure shift of the D-7(0)-F-5(0) fluorescence line of SrB4O7:Sm2+, in hydrostatic medium (helium) up to 124 GPa and in nonhydrostatic medium (H2O) up to 130 GPa. There is no quenching of the luminescence, in contrast to that observed in similar compounds. We show that this line permits more accurate pressure measurements at very high pressure than the commonly used R-1 emission line of ruby because it remains intense, sharp, well isolated from the other lines, and weakly dependent on nonhydrostaticity. The wavelength pressure shift of the D-7(0)-F-5(0) line is found to be very well represented by the nonlinear relation: P = 4.032 Delta lambda(1 + 9.29 x 10(-3)Delta lambda)/(1 + 2.32 x 10(-2)Delta lambda) with P in GPa and Delta lambda = lambda - 685.41 in nm. High temperature experiments up to 900 K at room pressure were also performed. The negligible temperature dependence and the small thermal line broadening are further advantages for high pressure-high temperature studies in diamond anvil cells. A metrology for in situ measurements of pressure and temperature, based on the combined use of this compound with ruby is also presented, along with a new calibration of the ruby R-1 frequency shift with temperature from 300 to 800 K. (C) 1997 American Institute of Physics.