EQUATION OF STATE OF WURTZITIC BORON-NITRIDE TO 66 GPA

The compressibility of wurtzitic boron nitride (wBN) taken in mixture with cubic BN has been measured at room temperature up to 66 GPa, usin g a diamond anvil cell and powder diffraction of synchrotron radiation . From the obtained pressure-volume relation for wBN the isothermal bu lk modulus of B-0=375+/-9 GPa and its first pressure derivative of dB( 0)/dp=4.9+/-0.7 have been calculated indicating that this phase has ne arly the same compressibility as cBN (B-0=377+/-4 GPa and dB(0)/dp=4.1 +/-0.2). Thermodynamic calculations using our findings on wBN equation of state have shown that wurtzitic boron nitride is metastable over t he whole ranges of pressures and temperatures. (C) 1998 American Insti tute of Physics. [S0003-6951(98)03414-7].