Materials science: The hardest known oxide

  title={Materials science: The hardest known oxide},
  author={Leonid S. Dubrovinsky and Natalia Dubrovinskaia and Varghese Swamy and J. Muscat and Nicholas M. Harrison and Rajeev Ahuja and Bengt Holm and B{\"o}rje Johansson},
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… Expand
High-pressure structural phase transitions in TiO2 and synthesis of the hardest known oxide
Despite great technological importance and many investigations, a material with a measured hardness comparable to that of diamond or cubic boron nitride has yet to be identified. Our combinedExpand
Nanotwin hardening in a cubic chromium oxide thin film
NaCl-type (B1) chromium oxide (CrO) has been expected to have a high hardness value and does not exist as an equilibrium phase. We report a B1-based Cr0.67O thin film with a thickness of 144 nmExpand
Hardness of cubic silicon nitride
We report that polycrystalline cubic-Si 3 N 4 with a spinel structure and low oxygen concentration (<0.5 wt%) shows Vickers hardness of 43 GPa when measured with the indentation load of 10 mN. TheExpand
3.02 – From Diamond to Superhard Borides and Oxides
In the last decade, major advances in technology have helped the development of new materials with superhard properties. The synthesis of many of these materials is either consistent with theory orExpand
Superhard Ceramic Oxides
Oxide-based ceramic materials are rapidly proving to have exciting potential for application as hard coatings. The most commonly known oxide material is silica, with a well-known variety ofExpand
Synthesis of nanocrystalline bulk SiO2 stishovite with very high toughness
Nanocrystalline bulk stishovite, with pure SiO 2 composition, was synthesized under high pressure and temperature. We found that this material has an extremely high fracture toughness (∼13 MPa m 1/2Expand
From superhard to hard: A review of transition metal dioxides TiO2, ZrO2, and HfO2 hardness
The high-pressure, high-temperature behavior of transition metal dioxides TiO2, ZrO2, and HfO2 has been reviewed. In particular, early predictions and measurements that suggested superhard behaviorExpand
Structural similarities between Ti metal and titanium oxides: implications on the high-pressure behavior of oxygen in metallic matrices
The stabilities of the body-centered-tetragonal and distorted-diamond phases of titanium are investigated by first-principles methods. Our results, together with previous experimental and theoreticalExpand
Hardness calculations of 5d transition metal monocarbides with tungsten carbide structure
The electronic and elastic properties of 5d transition metal monocarbides with tungsten carbide structure have been studied by first principles calculations. The calculated lattice parameters,Expand
Elastic properties and 2D icosahedral bonding in borides of hexagonal WC type
Abstract Using ab initio calculations we have identified materials with bulk moduli comparable to cubic BN. These are WB, IrB, ReB and OsB crystallizing in the hexagonal WC structure. In the (0 0 0Expand


Transition-metal dioxides with a bulk modulus comparable to diamond
Recently it has been reported that a high-pressure cubic phase of ruthenium dioxide has an unusually large bulk modulus, and consequently is a most interesting candidate as a very hard material.Expand
Electronic mechanism of hardness enhancement in transition-metal carbonitrides
Transition-metal carbides and nitrides are hard materials widely used for cutting tools and wear-resistant coatings. Their hardness is not yet understood at a fundamental level. A clue may lie in theExpand
Carbon nitride and other speculative superhard materials
Abstract In 1984, the author predicted in an unpublished patent disclosure letter at the Diamond Technology Center of Norton Company that C3N4 may be harder than diamond, the hardest material known.Expand
X-ray diffraction study of TiO2 up to 49 GPa
Abstract TiO 2 (anatase) was studied up to 49 GPa in a diamond anvil cell by angle-dispersive X-ray diffraction. Two phase transitions were observed, the first to the orthorhombic α-PbO 2 -type phaseExpand
Computational Alchemy: The Search for New Superhard Materials
A central challenge to modern materials science is the rational design and synthesis of new materials possessing exceptional properties. Recent advances in first-principles modeling methods and theExpand
On the rutile/α-PbO2-type phase boundary of TiO2
Abstract The high-pressure, high-temperature phase equilibria of TiO2 have been studied with special emphasis on the rutile and α-PbO2-type phases. It is found that the phase boundary, when plottedExpand
Predicting properties and new materials
Abstract The development and application of a “Standard Model” of solids are described with emphases on the capacity of the model for predicting solid state properties and the existence of newExpand