5:15 PM - 6:45 PM
[SMP24-P14] Validation of Pressure Calibration Methods for Diamond Anvil Cell under Low Pressure Conditions
Keywords:Diamond anvil cell, Raman spectroscopy, Diamond anvil Raman barometer, Quartz Raman barometer, Ruby fluorescence
We verified the Raman shifts of quartz and diamond anvils as a Raman pressure sensor for diamond anvil cell (DAC) experiments under low pressure conditions of a few GPa. In a previous study[1], the Raman shift of quartz was calibrated under low pressure conditions. However, the pressure condition is limited because the intensity of quartz Raman peak is weak and the phase transition to coesite occurs at about 2 GPa. On the other hand, diamond anvils have the advantage of a large Raman peak intensity, but because of the presence of a pressure gradient within the anvil, a calibration method using high-frequency edges has been adopted, and no analysis method has been established under low pressure conditions where the high-frequency edge is not distinct.
In this experiment, quartz and ruby powder were packed in a rhenium gasket, and a water/ethanol mixture was sealed as the pressure medium. Pressure was determined from the wavelength shift of ruby fluorescence [2], and DAC experiments were performed under seven different pressure conditions ranging from 200 MPa to 1500 MPa. Several candidates for defining the high-frequency edge of the diamond anvil were considered, for example, varying the number of peaks to be set or taking differential values.
As a result, a linear relationship with pressure was observed for the 464 cm-1 peak shift of quartz, consistent well with the relational equation from a previous study [1]. It also agreed well with proposed equation using the peak-to-peak distance between 464 cm-1 and 206 cm-1[3], but the 206 cm-1 peak was sometimes obscured, resulting in a maximum error of ±200 MPa. The pressure calibration equation for the high wavenumber end of the diamond anvil was represented by a quadratic curve, with an error of 200 to 300 MPa. The reason for the relatively large error in the estimated pressure is thought to be the effect of the drift of the Raman peak position due to changes in room temperature. Therefore, the method of calibrating the Raman peak shift at each measurement is considered to be effective.
[1] Schmidt & Ziemann (2000), [2] Piermarini et al. (1975), [3] Tomioka et al. (2022)
In this experiment, quartz and ruby powder were packed in a rhenium gasket, and a water/ethanol mixture was sealed as the pressure medium. Pressure was determined from the wavelength shift of ruby fluorescence [2], and DAC experiments were performed under seven different pressure conditions ranging from 200 MPa to 1500 MPa. Several candidates for defining the high-frequency edge of the diamond anvil were considered, for example, varying the number of peaks to be set or taking differential values.
As a result, a linear relationship with pressure was observed for the 464 cm-1 peak shift of quartz, consistent well with the relational equation from a previous study [1]. It also agreed well with proposed equation using the peak-to-peak distance between 464 cm-1 and 206 cm-1[3], but the 206 cm-1 peak was sometimes obscured, resulting in a maximum error of ±200 MPa. The pressure calibration equation for the high wavenumber end of the diamond anvil was represented by a quadratic curve, with an error of 200 to 300 MPa. The reason for the relatively large error in the estimated pressure is thought to be the effect of the drift of the Raman peak position due to changes in room temperature. Therefore, the method of calibrating the Raman peak shift at each measurement is considered to be effective.
[1] Schmidt & Ziemann (2000), [2] Piermarini et al. (1975), [3] Tomioka et al. (2022)