High-pressure synthesis, characterization, and equation of state of cubic C-BN solid solutions
- Department of Earth Sciences and Institute of Tectonics, University of California, Santa Cruz, California 95064 (United States)
- Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90024 (United States)
- Department of Geology and Geophysics, University of California, Berkeley, California 94720 (United States)
- Department of Physics, University of California, Berkeley and Materials Science Division, Lawrence Berkeley Laboratory, Berkeley, California 94720 (United States)
Synthesis of several samples across the cubic C{sub {ital x}}(BN){sub 1{minus}{ital x}} solid solution ({ital x}=0.3--0.33,0.5,0.6) at pressures in excess of 30 GPa and temperatures above 1500 K indicates that they are isostructural with diamond and cubic BN (borazon). Measurement of the lattice parameters of C-BN samples quenched to ambient conditions shows that the solid solution between C (diamond) and cubic BN is nonideal, with unit-cell volumes up to 1% larger than predicted based on ideal mixing (Vegard`s law). In addition, we have measured the zero-pressure, 300-K vibrational spectra for C{sub 0.3}(BN){sub 0.7}. In the midinfrared absorption spectrum, we observe a reststrahlen band ranging from 1000--1120 cm{sup {minus}1}, and the Raman spectrum has a longitudinal optic mode at 1323({plus_minus}2) cm{sup {minus}1}. Based on a comparison of the spectrum with that of diamond and cubic BN, we conclude that the bonding in cubic C-BN is partially ionic. In addition to these measurements on quenched samples, we have measured the isothermal bulk modulus of C{sub 0.33}(BN){sub 0.67} by x-ray diffraction through a diamond cell to over 100 GPa at 300 K. The bulk modulus is 355({plus_minus}19) GPa, which is lower than those of diamond, cubic BN and the value predicted from ideal mixing between the end members, but is consistent with the nonideal expansion observed for the cubic C-BN lattice parameters.
- Research Organization:
- Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
- DOE Contract Number:
- AC03-76SF00098
- OSTI ID:
- 44570
- Journal Information:
- Physical Review, B: Condensed Matter, Vol. 51, Issue 18; Other Information: PBD: 1 May 1995
- Country of Publication:
- United States
- Language:
- English
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