The diamond C13/12C isotope Raman pressure sensor system for high-temperature/pressure diamond-anvil cells with reactive samples

Abstract

By using a thin C13 diamond chip together with a C12 diamond chip as sensors, the diamond Raman spectra provide the means to measure pressure precisely (±0.3 GPa) at any temperature (10–1200 K) and simultaneous hydrostatic (or quasihydrostatic) pressure (0–25 GPa) for any sample compatible with an externally heated diamond-anvil cell. Minimum interference between the Raman spectrum from the diamond anvils and those of the pressure sensors is obtained by measuring pressures with the Raman signal from the C13 diamond chip up to 13 GPa, and that from the C12 chip above 10 GPa. The best crystallographic orientation of the diamond anvils is with the [100] direction along the direction of applied force, in order to further minimize the interference. At 298 K, the pressure dependence of the C13 diamond first-order Raman line is given by ν(P)=νRT+aP for 91 at. % C13 diamond, where νRT(13C)=1287.79±0.28 cm−1 and a(13C)=2.83±0.05 cm−1/GPa. Analysis of values from the literature shows that the pressure dependence of the Raman line of C12 diamond is best described by the parameters νRT(12C)=1332.5 cm−1 and a(12C)=2.90±0.05 cm−1/GPa. The temperature dependence of the diamond Raman line is best described by ν(T)−νRT=b0 for T⩽200 K, and ν(T)−νRT=b0+b1.5Tk1.5 for 200 K⩽T⩽1500 K, where Tk=T−200 K. For 91 at. %C13 diamond, the parameters are b0=0.450±0.025 cm−1;b1.5=−(7.36±0.09)×10−4 cm−1 K−1.5; and for C12 diamond, the parameters are b0=0.467±0.033 cm−1,b1.5=−(7.56±0.10)×10−4 cm−1 K−1.5. Although no quantitative theoretical models are available for calculating the Raman shift as a function of temperature, the excellent fits to the data suggest that the Tk1.5 dependence above has a physical basis.

In situ spectroscopic study of water speciation in the depolymerized Na 2 Si 2 O 5 melt

“…Temperature was controlled to ±1°C using the alumel-chromel thermocouples attached near the culet surfaces of the upper and lower anvils and calibrated to the melting points of NH 4 NO 3 (169.6°C), NaNO 3 (306.8°C) and CsCl (645°C). Pressures were calculated based on the measured Raman shift of 13 C diamond using the calibration of Schiferl et al (1997). Reproducibility of the 13 C diamond Raman shift measurement is estimated to be better than ± 0.5 cm − 1 , which translates into pressure uncertainty of less than ±0.2 GPa in the calibration of Schiferl et al (1997).…”

“…Pressures were calculated based on the measured Raman shift of 13 C diamond using the calibration of Schiferl et al (1997). Reproducibility of the 13 C diamond Raman shift measurement is estimated to be better than ± 0.5 cm − 1 , which translates into pressure uncertainty of less than ±0.2 GPa in the calibration of Schiferl et al (1997).…”

Diamond as pressure sensor in high‐pressure Raman spectroscopy using sapphire and other gem anvil cells

“…Some authors have investigated the possibility of using the Raman signal from the tip of the diamond anvil as an in situ pressure calibrant, 14,15 but this procedure has been proven to be unreliable in practice. 16 Some authors have tried this procedure for FTRaman experiments at high pressure, 17 but their pressure calibration was obtained under uniaxial conditions, and it is known that the shift of the triply degenerate diamond Raman band varies with the crystallographic orientation, 18 the type of sample and the gasket material used, because these affect the nature of the stresses on the anvil. Other possibilities include the use of a diamond chip inside the DAC 14 or a 13 Clabeled diamond chip, 16 since its Raman signal (1287.8 cm 1 at zero pressure) is well separated from the 1332.5 cm 1 band of natural diamond, etc.…”

Basic Properties of Diamond: Phonon Spectra, Thermal Properties, Band Structure

“…With these data, the Raman line may be used to measure the temperature of a diamond, or to measure a high pressure that the diamond is subjected to. For example, the pressure in a diamond anvil cell may be measured using the exact frequency of the Raman line from a 13 C diamond chip that has been included in the working volume of the cell [32], or by using the Raman signal from a 13 C isotopically enhanced diamond anvil [33].…”