High pressure phase transformations in neodymium studied in a diamond anvil cell using diamond-coated rhenium gaskets

Diamond anvil cells are used to generate high static pressures up to severa l megabars (hundreds of GPa) in very small volumes of material. We have exp lored a technique which employs a microwave plasma chemical vapour deposite d diamond layer on one side of the rhenium gasket. The high yield strength of the diamond layer prevents excessive thickness reduction of the sample i n the gasket hole. As a test case, we show energy dispersive x-ray diffract ion data on rare earth metal neodymium to high pressures of 153 GPa using a synchrotron source. The increased sample thickness results in an unambiguo us crystal structure determination of a monoclinic phase in neodymium above 75 GPa.