Despite great technological importance and many investigations, a material with measured hardness comparable to that of diamond or cubic boron nitride has yet to be identified. Combined theoretical and experimental investigations led to the discovery of a new polymorph of titanium dioxide with titanium nine-coordinated to oxygen in the cotunnite (PbCl2) structure. Hardness measurements on the cotunnite-structured TiO2 synthesized at pressures above 60 GPa and temperatures above 1000 K reveal that this material is the hardest oxide yet discovered. Furthermore, it is one of the least compressible (with a measured bulk modulus of 431 GPa) and hardest (with a microhardness of 38 GPa) polycrystalline materials studied thus far.
Cite
@article{arxiv.0907.1464,
title = {Cotunnite-structured titanium dioxide: the hardest known oxide},
author = {L. S. Dubrovinsky and N. A. Dubrovinskaia and V. Swamy and J. Muscat and N. M. Harrison and R. Ahuja and B. Holm},
journal= {arXiv preprint arXiv:0907.1464},
year = {2009}
}
Comments
This is full version of the paper published as Brief Communications in Nature, 410, 653-654