|About this Abstract
||Materials Science & Technology 2012
||Advances in Dielectric Materials and Electronic Devices
||The Effect of A-Site Vacancies on Cell Volume, Tolerance Factor, and TCF of Perovskites
||Rick Ubic, Steven Letourneau, Waltraud Kriven
|On-Site Speaker (Planned)
Point defects like vacancies can have a profound effect on the structure of perovskite ceramics, but the exact mechanisms by which they do this are unclear. A predictive model for the pseudocubic lattice constant of perovskites, based solely on published ionic radii data, has been developed and adapted as a model for tolerance factor. These models more consistently predict both pseudocubic lattice constant, hence cell volume, and the tolerance factor than existing methods, thus also more accurately modeling the temperature coefficient of resonant frequency (TCF). The relationship between tolerance factor and TCF is revisited. This model shows that the average A-site size decreases with increasing vacancy concentration, but not as much as would be expected if vacancies were truly zero-dimensional defects; instead, A-site vacancies posses an effective finite size due to mutual repulsion of the coordinating oxygen ions.