Ferroelectric Materials  

Our recent work has focussed on understanding the nature of ferroelectricity in the Aurivillius family of ferroelectrics, such as Bi₂WO₆, SrBi₂Ta₂O₉ and Bi₄Ti₃O₁₂. These materials are being used in information storage (FeRAM) technology. We have characterised in detail the structural basis for the ferroelectric behaviour in this family. We have also designed, prepared and characterised new ferroelectrics related to these materials, for example complex oxychloride derivatives such as Bi₃Pb₂Nb₂O₁₁Cl and also fluorinated derivatives. A current aim is to extend this work to multiferroic materials.  

Optical and Magnetic Materials  

Here we are exploring the solvothermal synthesis of new fluoride and oxyfluoride phases which are expected to show either luminescent, non-linear optical or magnetic properties. As examples of the first class we are preparing new lanthanide fluorides templated by organic cations, such as [C₂N₂H₁₀]_0.5[Y₂F₇], which shows promising luminescent properties on doping with suitable lanthanides. In the latter cases, we are interested in preparing oxyfluorides based on highly polar d⁰ or d¹ cation-centred octahedra (such as Nb⁵⁺, W⁶⁺, V⁴⁺ etc). Being able to arrange these electronically-active units in ordered solid-state arrays is the key to controlling their physical properties.