Pressure measurements within optical cells using diamond sensors: accuracy of the method below 1GPa

The accuracy of the diamond pressure gauge has been investigated in the moderate pressure range (0-1 GPa) between 210 and 310 K. Experiments have been conducted using a sapphire anvil cell coupled to a Raman spectrometer. The temperature shift of the first-order Raman peak of diamond is very small (-7.56 x 10(-4) cm(-1)/K-1.5), which confirms previous results obtained on a wider temperature range. Such a trend implies a very small shift over the studied temperature range, of the same order than the dispersion due to external factors (isotopic composition, orientation). The pressure dependence is found equal to 3.20 (+/- 0.02) cm(-1)/GPa. A statistical description of the data is provided. indicating that the diamond gauge provides pressure estimates below 1 GPa with an accuracy of 39 MPa. Application of these results to science fields involved in the moderate pressure range below 1 GPa is discussed.