High-pressure study of low-compressibility Ta2N

Room temperature synchrotron x-ray diffraction experiments were performed on nanocrystal Ta2N in a diamond anvil cell to a pressure of 55.48 GPa. This nitride is a well-known kind of high-hardness material, and it is found to be highly incompressible. The structure is stable with no phase transitions observed in this pressure range. The zero-pressure bulk modulus and its pressure derivative at ambient pressure are B0 = 360 +/- 3 GPa, B0' = 4, and in room conditions, the a and c parameters are 3.054 A, 4.996 A, respectively. The bulk modulus of Ta2N is greater than those of TaC, epsilon-TaN, Cr2N and MoN. The differences in bulk moduli might be due to the differences in structure and the cohesive energy among these phases.