Pyrochlores
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Pyrochlore lattice structure compounds -A2B2O7 have shown significant promise as ideal candidates for applications ranging from electronic materials and solid electrolytes, to heating elements, high temperature electrodes and fixation of radioactive waste. This versatility depends on the fact that the Pyrochlore crystal structure allows a wide variety of ionic substitutions at both the A, B sites as the B element can be a transition metal, with variable oxidation state, and the A element can be a rare earth or an element, with inert lone pairs; At the same time they satisfy other requirements such as physical stability, chemical or thermal compatibility with other materials involved in the design.
Interest in 2nd and 3rd row pyrochlores is exemplified by recent results on (Cd,Hg)2Os2O7, Cd2Nb2O7, Cd2Re2O7 and K(Rb)Os2O6. We intend to develop this work through a major effort synthesising and characterising, structurally and in terms of electronic/magnetic properties transition metal pyrochlores of the type A3+2B4+2O7 and A2+2B5+2O7 .
The Pyrochlore showing rings of BO6 octahedra in green, A cations in grey and non-polyhedral oxygens in cyan.
Our current studies focus on the optimization of pyrochlore structures with transition metals including Ru, Mo and Nb. Primary analysis is by X-Ray diffraction for structural refinement. This information can be used to develop new compositions that might better optimize the properties for particular applications. Future work will extend these ideas to other pyrochlore systems and may include more adventurous synthetic methods like those described in the High Pressure pages.
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