Thermal expansion behavior of a shock-synthesized B-C-N heterodiamond

The thermal expansion coefficient of BC2.5N heterodiamond determined by means of high-temperature X-ray diffraction, is negligible up to 800 degrees C, it changes abruptly in the range 900-1100 degrees C and increases steadily above 1100 degrees C. The thermal expansion coefficient is ca. 5.5 x 10(-6) K-1 in the range 1100-1300 degrees C. This expansion coefficient is in fairly good agreement with that of cubic BN at high temperatures. The rapid expansion preceding the steady expansion is unknown for diamond and cubic BN. The thermal expansion behavior is discussed from a structural viewpoint.