School of Chemistry Colloquium: Professor Derek Sinclair (University of Sheffield) Tuning the electrical properties of B-site d0 perovskites for electrostatic energy storage multi layer ceramic capacitors.

School of Chemistry Colloquium for final year project students, MSc students PhD students, post-doctoral researchers and academic staff.

There are over 3 Trillion Multi-Layer Ceramic Capacitors (MLCCs) produced annually for a variety of applications, eg mobile phones. These are based on the ferroelectric perovskite BaTiO3 and are engineered to have core-shell microstructures via chemical doping to impart the desired electrical properties. Despite the success of BaTiO3, the demands for MLCCs to operate under more demanding conditions (e.g higher temperature (> 150 oC) and voltage (> 50 V)) and/or with substantially enhanced discharge energy density (> 10 J/cm3) has shifted the search onto other polar perovskites such as NaNbO3 and/or solid solutions between these materials. Here we will: (i) use a resource efficient method to explore the solid solution between NaNbO3-BaTiO3 to develop the concept of a temperature stable bi-layer MLCC; (ii) establish the influence of aliovalent dopants (A-site donors and B-site donors and acceptors) on the electrical properties of NaNbO3 to obtain an improved understanding of its basic defect chemistry; and (iii) develop a range of nominally stoichiometric solid solutions based on NaNbO3-SrTiO3­-La(Mg1/2Ti1/2)O3 that traverse from conventional to relaxor ferroelectric to incipient ferroelectric/quasi-linear dielectrics, the latter of which exhibit high discharge energy densities, > 40 J/cm3.