High-temperature ovens (1700 °C) for a wide range of oxygen gas pressures (10-6–2×103 bar): A new two-chamber autoclave.

We describe the construction of four different systems used for annealing samples in oxygen. The gas pressure can be controlled over nine decades (10[sup -6]-2 × 10³ bar). The maximum temperature, 1700 °C, is limited by the ceramic materials used for thermal insulation and for the crucibles. The low-pressure furnaces (10[sup -6]-1 bar) have an external heating system and incorporate an active regulation of a small gas flow. The intermediate pressure furnaces (1-150 bar) are heated either by a special resistive wire or by rf heating with a Pt-20%Rh susceptor, both in the pressurized gas chamber. Quenching is possible in the latter. For the kbar range, we designed a double-chamber autoclave with separate heater and sample spaces, filled with Ar and O[sub 2]. The gas pressures are balanced in a cold, separate vessel by means of a silicon hose. The temperature is measured with a thermocouple feeding into the hot, pressurized oxygen environment very close to the sample. The construction problems of this new autoclave have been solved with particular emphasis on the safety requirements. [ABSTRACT FROM AUTHOR]