Materials science: The hardest known oxide

@article{Dubrovinsky2001MaterialsST,
  title={Materials science: The hardest known oxide},
  author={Leonid S. Dubrovinsky and Natalia Dubrovinskaia and Varghese Swamy and Joseph Muscat and Nicholas M. Harrison and Rajeev Ahuja and Bengt Holm and B{\"o}rje Johansson},
  journal={Nature},
  year={2001},
  volume={410},
  pages={653-654}
}
A material as hard as diamond or cubic boron nitride has yet to be identified, but here we report the discovery of a cotunnite-structured titanium oxide which represents the hardest oxide known. This is a new polymorph of titanium dioxide, where titanium is nine-coordinated to oxygen in the cotunnite (PbCl2) structure. The phase is synthesized at pressures above 60 gigapascals (GPa) and temperatures above 1,000 K and is one of the least compressible and hardest polycrystalline materials to be… 

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