Synthesis of diamond in double carbon-rare earth element systems

Abstract For the first time, a possibility of diamond synthesis under high pressures was studied in binary systems “rare earth element (REE)-carbon” with refractory carbides. It was found that at pressure 8 GPa in the Eu-C system graphite transforms into diamond at about melting temperature of EuC 2 carbide (1900–2200 °C), while in the Er-C and Tm-C systems diamond formation takes place well below melting temperature of carbides ErC 2 or TmC 2 (1600–1800 °C). Simultaneous crystallization of diamond and carbides ErC 2 or TmC 2 from vanishing carbon-saturated liquid phase was proposed as a mechanism for the diamond formation in the latter systems. As compared with Eu, more strong catalytic activity of Er and Tm for diamond synthesis was explained by matching their crystal structures to the diamond one.