High-pressure High-temperature Synthesis And Characterization Of Large Single Crystal Of CBN

Cubic boron nitride?cBN?is a superhard material with a hardness second only to diamond,with many excellent properties.However,as an important superhard semiconductor,cBN single-crystal preparation technology lags far behind that of diamond,which seriously hinders its application and development in precision machining,third-generation semiconductors,and spectroscopic devices.Hence,technological development for preparing cBN large single crystal is not only an urgent matter,but also an important opportunity for China's superhard industry to achieve breakthroughs.This project intends to improve high-temperature high-pressure technology for synthesizing large cBN single crystal,and prepare high-grade large-size cBN single crystal as important material carriers for third-generation semiconductors,optical devices,and quantum chips.In the meantime,research was done on the preparation of boron-doped graphite heaters to overcome the temperature limit of Kawai type two-stage high pressure apparatus.It will lend support to high-pressure experimental research in general,and insitu synchrotron X-ray study in particular.This project relies on the domestic DS6 × 10 MN hinged six-sided cubic press,using h BN powder as the main raw material and Mg₃N₂ as the catalyst material,to conduct a series of comparative studies on the methods and processes for the synthesis of cBN single crystal.The main research contents are: the preparation and purification of cBN single crystal;studying the influence of different parameters-pressure,temperature,duration-on the production and the size of cBN crystal;and the synthesis of millimetersized cBN single crystal by new assembly method,which provides experimental and theoretical basis for the industrial production.In addition,the ultra-high temperature boron-doped graphite heater was prepared,and its performance was experimentally tested.Using Mg₃N₂ as the catalyst material,we have successfully synthesized cBN single crystals using a domestic DS6 × 10 MN hinged six-sided cubic press,and the optimal synthesis parameters were determined through three sets of comparative experiments.Under optimal condition?at 5.5 GPa and 1500 ? for 60 min?,the yield reached nearly 90%,and the size of the single crystal was up to 600 ?m;The new layered assembly was used to synthesize the millimeter-sized cBN single crystal,with the maximum sizereaching 1.5 mm.The Vickers hardness of the single crystal was 53 GPa.The newly developed boron-doped graphite heater,together with the self-made MgO octahedral pressure transmission medium and Cr O insulator successfully achieved an internal temperature of nearly 3000 ?.High heating efficiency and stable process provide good conditions and support for the subsequent synthesis and research of new materials.