A temperature of 3500 °C was generated using a diamond resistance heater in a large-volume Kawai-type high-pressure apparatus. Re and LaCrO3 have conventionally been used for heaters in high-pressure studies but they cannot generate temperatures higher than 2900 °C and make in situ x-ray observations difficult due to their high x-ray absorption. Using a boron-doped diamond heater overcomes these problems and achieves stable temperature generation for pressure over 10 GPa. The heater starting material is a cold-compressed mixture of graphite with boron used to avoid the manufacturing difficulties due to the extreme hardness of diamond. The diamond heater was synthesized in situ from the boron-graphite mixture at temperature of 1600±100 °C and pressure of 20 GPa. By using the proposed technique, we have employed the diamond heater for high-temperature generation in a large-volume high-pressure apparatus. Achievement of temperatures above 3000 °C allows us to measure the melting points of the important constituents in earth's mantle (MgSiO3, SiO2, and Al2 O3) and core (Fe and Ni) at extremely high pressures.
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