Francisco Javier Martín Gil

New carbon-nitrogen materials. A likely alternative to diamond

Abstract In a recent work Liu and Cohen ( Phys. Rev. B., 41 (1990) 10 727-10 734) reported the theoretical prediction of a C-N phase whose hardness was competing with that of diamond. This work provoked extensive experimental search for the theoretical material with a composition β -C 3 N 4 . There was a report (Niu, Lu and Lieber, Science, 261 (1993) 334–337) on the growth β -C 3 N 4 films. However, this has not been reproduced by others workers. Recently, Guo and Goddard ( Chem. Phys. Lett., 237 (1995) 72) reported that the synthesized material, in most cases, corresponds to α -C 3 N 4 and not to β -C 3 N 4 . We review the evidence from a number of papers and conclude that there is not enough evidence that C 3 N 4 can be produced as large crystals. It is clear, however, that the α -C 3 N 4 is more stable than the β -C 3 N 4 phase. We discuss the recent report (Sarikaya, Qian, Martin-Gil, Martin-Gil and Jose-Yacaman, to be published) in which a new phase with the composition α -C x N y with x 4 and y 4 is found. We discuss the applications and future trends on these materials.