A diamond gasket for the laser-heated diamond anvil cell

Advances in laser heating techniques with diamond anvil cells have enabled direct investigations of materials under extreme pressure-temperature conditions. The success of uniform heating to the maximum temperatures at megabar pressures relies critically on maximizing the gasket thickness which in turn depends upon the shear strength of the gasket. We have used diamond powder, the strongest possible material, to formulate a gasket for in situ x-ray diffraction with double-sided laser heating. The increase in gasket thickness allows increases in sample and insulator thickness, thereby improving the quality and pressure-temperature range of the measurement. We did not observe any pressure difference within 40 μm of the center of the sample chamber and the temperature distribution across the sample itself is within ±47 K. These improvements as well as the fact that the diamond gasket can allow the sample to remain in good condition after high P-T processing make it an extremely useful technique in diamond cell laser-heating experiments. As an example of the technique, we present in situ x-ray diffraction results for FeO to above 86 GPa and 3500 K.