A Calculation of the Dielectric Constant of Fine Grained Barium Titanate from Single Crystal Constants.

摘要

The dielectric constant of K of fine-grained BaTiO3at 25C is calculated in terms of the single crystal constants. Following the lead of earlier authors,it is shown that the internal stresses in the ceramic caused by the deformation of the crystallites from the cubic to the tetragonal phase are sufficient to account for an anomalously large K. It is shown further that the mutual electrostatic interaction between the grains also tends to increase the value of K. The model used in this paper for computing the elastic interaction consists of a spherical crystallite deforming against the elastic opposition of the surrounding medium. This medium was treated by us initially as homogeneous and isotropic. Calculations based on this assumption result in internal stresses which are so large that the ceramic must be paraelectric at 25C. The model was then modified phenomenologically to permit the presence of local order,and more realistic results were obtained. However,the idea of local order is merely introduced in this paper and further development is needed. (Author)