Antiferroelectric Tetragonal Tungsten Bronzes

Recently the presence of two phase transitions on heating in K2(La0.75Pr0.25)Nb5O15 has been observed and have been assigned to successive ferro- (FE) to antiferro- (AFE) to para-electric (PE) transformations. This composition is of particular interest as the room temperature AFE phase results in a high and voltage stable permittivity (and hence capacitance) under large applied electric fields. As a result these materials can be utilised in high capacitance, high voltage multi-layer capacitors (MLCs). We aim to determine the underlying crystallographic changes associated with the FE-AFE transition, and also an in-situ study of MLCs fabricated from this material under an applied electric field. These studies will give us an atom-scale insight into the origin of the properties of this materials allowing development of further materials for application as high voltage capacitors.