Study on Wurtzite Type Boron Nitride and Its Applications (Ⅱ)Isothermal Equation of State for Wurtzite Type Boron Nitride

In our experiments, the isothermal equation of state of wBN is studied by two different in situ high pressure X-ray diffraction methods at room temperature. The sample is obtained by shock compression. One of the methods is the rotating anode X-ray angle dispersive powder diffraction by which wBN is studied up to 40 GPa. The results indicated that wBN is structurally stable below 40 GPa and no phase transition is observed. The Murnaghan isothermal equation of state for the sample is fitted with the bulk modulus at zero pressure, B0=(33534) GPa, and its pressure deviation B0'=4.21. The other method is the synchrotron radiation X-ray energy dispersive diffraction (EDXD) by which the isothermal equation is studied with improved MaoBell type diamond anvil cell up to 25 GPa. The loading mechanism of the improved DAC is stepping and automatic, which maintains the fixed scattering angle. The Murnaghan isothermal equation is also fitted with the bulk modulus at zero pressure, B0=(28056) GPa, and its pressure deviation B0'=4.39.