High-pressure high-temperature synthesis of novel binary and ternary nitride phases of group 4 and 14 elements

Our recent experiments on high-pressure high-temperature synthesis of novel ternary nitrides of group 4 and 14 elements are presented. Dense carbon nitride imide, C2N2(NH), was synthesized for the first time in a laser heated diamond anvil cell (LH-DAC) at pressures above 27 GPa and temperatures around 2000 K. Based on results of the electron diffraction-, EELS-and SIMS-measurements combined with theoretical calculations the structure of this new C-N-H phase was suggested to be of the defect-wurtzite type. Farther, macroscopic amounts of a new oxynitride of zirconium having cubic Th3P4-type structure, c-Zr2.86(N0.88O0.12)4, were synthesized at high pressures and temperatures using a multi-anvil apparatus. Earlier this structure was observed for binary nitrides of zirconium(IV) and hafnium(IV) synthesized in microscopic amounts in a LH-DAC. The lattice parameter of c-Zr2.86(N0.88O0.12)4 was found to be a0 = 6.7549(1) A which is slightly larger than that of c-Zr3N4. Isotropic bulk and shear moduli of c-Zr2.86(N0.88O0.12)4 of B0 = 219 GPa and G0 = 96 GPa, respectively, were determined from the compression and nanoindentation measurements. The Vickers microhardness, HV(1), of the porous (about 30 vol. %) sample of c-Zr2.86(N0.88O0.12)4 was measured to be 12 GPa, similar to that of single crystal δ-ZrN