High-pressure synthesis and characterization of diamond from europium containing systems

Abstract

Experimental studies have been carried out on diamond synthesis in Mg-based systems with additions of europium in various charge states, including Eu0, Eu2+, and Eu3+. The experiments were carried out at a pressure of 7.8 GPa and a temperature of 1800 °C. Metallic Eu, Eu-oxalate, Eu-carbonate, Eu2O3, EuCl3, EuF3, and EuF2 were used as additives. The influence of the content of Eu-containing compounds on diamond crystallization and the photoluminescence characteristics of synthesized diamonds was determined. The addition of europium compounds to Mg-based systems in all cases had an integral inhibitory effect on the diamond crystallization process, which manifested in a decrease in the degree of graphite conversion to diamond, a decrease in the diamond growth rate, and the appearance of metastable graphite. It was found that the inhibiting ability of europium compounds decreased in the following sequence: Eu-oxalate > Eu-carbonate > EuCl3 > Eu2O3 > metallic Eu > EuF3 > EuF2. Spectroscopic studies of the synthesized diamonds revealed a new defect center manifesting in photoluminescence as an optical system with a zero-phonon line structure at 502 nm. The center was tentatively assigned to defects involving Eu impurities and the main factors controlling the formation of the 520 nm center were determined.