Internal resistive heating in diamond anvil cell for in situ x-ray diffraction and Raman scattering

An internal resistive heater contained completely between the anvil faces of a diamond anvil cell has been used to conduct experiments up to 10 GPa and temperatures up to 3000 K. There is evidence that pressures up to 50 GPa can be achieved with smaller anvil faces and smaller heater assembly. The technique offers a very homogeneous temperature profile and excellent time stability for studying both metallic and nonmetallic materials. Temperature is measured by spectroradiometry as an image of the incandescent sample is projected onto the end of a fiber optic cable leading to a spectrometer. A very linear relationship between temperature and power provides accurate temperature measurements even when the temperature is below incandescence. The melting of gold determined by loss of diffraction peaks occurred at temperatures in good agreement with published values. In situ Raman spectra of SiO2 revealed the conversion of quartz to coesite. This method offers a larger heating volume with more stable and uniform temperature than laser heating techniques and at temperatures much greater than those that can be achieved by external resistive heating techniques.