Based on the generation of high pressure up to 10 GPa by using belt-type high pressure (HP) apparatus, technological development in the control of high temperatures (HT) up to 3200 °C was introduced. As a heat treatment effect under HP-HT up to about 3200 °C in the 2.5 GPa region, the two-dimensional turbostratic layer structure boroncarbon-nitride (BCN) was well crystalized into a-b and a-a’ stacked form was obtained. Heat treatment of high purity hexagonal boron nitride (hBN) with graphite above 2000 °C, carbon-doped hBN crystals with new color center were obtained. As an example of material synthesis by solid-phase reaction under HP, the thermophysical properties of cubic BN crystals, which are super-hard materials, were controlled. In terms of temperature dependence of thermal conductivity, concentration to boron (B) isotope of 10B or 11B increased nearly twice that of the natural isotope cBN, and a value close to that of diamond was obtained. Since these HP synthesis environments are single-shot batch processing, it is relatively easy to grasp the contamination components of the reaction system even above 2000 ℃. It is also emphasized that trial and error by combining various material systems, reaction control by sealing volatile components during synthesis, etc. are possible.