The project entails cooperative research of complex ferroelectric oxides between the group from the University of Tennessee at Knoxville, USA, and the group from A. F. Ioffe Physico-Technical Institute, Russian Academy of Science, St. Petersburg, Russia. It addresses some of the most important unsolved and current problems in the field of ferroelectric materials. In particular it aims at 1) identification of the atomistic origin of a relaxor behavior in Pb-based magnesium-niobate perovskite, 2) examination of dynamic and structural instabilities leading to phase transitions in Na-based niobate perovskite, and 3) elucidation of the structural factors resulting in a relaxor transition in solid solutions of Na niobate perovskite. Advancing this knowledge would greatly facilitate development of lead-free relaxor piezoelectric materials. The main reason hindering the understanding of the atomistic mechanism of the relaxor behavior is strong displacive and chemical disorder in the local atomic structure which frustrates conventional structural and dynamical studies. The project will leverage complementary research expertise of the two groups in applying neutron and X-ray scattering to study lattice dynamics and local atomic structure of the complex ferroelectrics. The US group will focus on powder samples and local structural methods whereas Russian group will be additionally examining single crystals. The local atomic structure will be studied by the atomic pair distribution function method that has proven to be very effective in determination of atomic displacements and disorder. Complementary detailed studies of lattice dynamics (phonons) in single crystals will be performed by the Russian researchers. The emphasis will be placed on understanding physics behind the giant dielectric response of lead-free relaxor-like solid solutions and critical dynamics and structural instabilities. The project will have broad impact for society and industry by advancing knowledge for the development of environmentally benign piezoelectric ceramics. Traditional materials, based on lead can create health hazards. The results will be quickly disseminated to contribute to education and stimulate research and development. The collaborative framework of this project will allow training of graduate and undergraduate student in new experimental techniques and involve them into science and technology of ferroelectric materials. This approach will enhance quality of education and promote new ideas through the exchange visits and collaborative experiments.
