A new high pressure and high temperature synthesis idea: Preparation of Micron polycrystalline transparent cubic boron nitride

A novel high-pressure and high-temperature method has been developed to synthesise micron-sized polycrystalline transparent cubic boron nitride (MPT-cBN). Utilising this technique, polycrystalline cubic boron nitride (PcBN) prepared at 15 GPa and 1500 °C with a grain size of 1–2 μm exhibits enhanced transparency and boasts a Vickers hardness of 68 GPa, resulting in the successful synthesis of superhard MPT-cBN. As a comparison, PcBN sintered at the same conditions by traditional methods lacks transparency and has a hardness that is 10 GPa lower than that obtained by the novel sintering method. This method could improve the transparency of MPT-cBN, which consequently elevates its hardness. Additionally, the sintering temperature of MPT-cBN is appropriately decreased by the new method, providing practical guidance for optimising the performance of other superhard, transparent materials and decreasing the sintering temperatures of materials such as diamond.