Research Fellows Directory
Dr Finlay Morrison
University of St Andrews
Ferroelectrics (FEs) exhibit spontaneous and reversible polarisation under an applied electric field; they have diverse applications with an annual worldwide market of $20-30 billion. The main applications are in the 1000 billion-plus capacitors produced annually, non-volatile memory chips in smart cards and also piezoelectric transducers for medical ultrasound, sonar and fuel injectors. Current limitations are the operating temperature range for capacitors and toxicity of materials in piezoelectric devices. In summary, we need new (Pb-free) materials with comparable/better performance than current ones.
My research investigates novel materials exhibiting both FE and magnetic properties; this includes both “magnetoelectrics” (coupling between magnetic and electric order) and “multiferroics” (exhibiting ferroelectricity and ferromagnetism). Multiferroics have two electrical (“up” and “down”) and two magnetic (N and S) states offering exciting new possibilities for the interaction of magnetic and electric fields with matter. My research in this area has included perovskite oxides which are attractive due to their simple structure; recently we have determined the structural behaviour of the important material, BiFeO3, as function of temperature. We are also developing tungsten bronzes, which are closely related to perovskites and offer similar compositional flexibility, however, our understanding of how to “tune” the properties of such materials is poor by comparison. We have been systematically investigating the composition/crystal structure/properties inter-relationships in an attempt to develop a global understanding of these materials.
These systems exhibit great potential for future devices and, so far, we have determined a number of key factors in controlling the dielectric behaviour of these materials viz. cation size effects (both crystal anisotropy and cation size variance) and the presence of charged defects in the form of “missing atoms” (vacancies).
Interests and expertise (Subject groups)