Pressure and temperature control in flat-belt type high pressure apparatus for reproducible diamond synthesis

This paper describes a technique on the pressure and temperature control in flat-belt (FB) type high pressure apparatus to conduct stable diamond synthesis study. We present results on the reproducibility of the sample pressure and temperature in different sets of diamond synthesis runs. We propose a method of monitoring these variations by the measurements of anvil displacement as a function of press load, and of heater resistance as a function of input power to the heater in every high pressure run. We examined pressure and temperature region of diamond formation in graphite-solvent metal systems, and propose a method to estimate the absolute pressure and temperature of the sample based on the graphite-diamond equilibrium curve. From these data, we conclude that the pressure and temperature of the sample in FB type high pressure apparatus can be estimated and controlled within about 3%. (C) 1999 Elsevier Science S.A. All rights reserved.