Domain Effects in Polycrystalline Barium Titanate

Abstract

Upon depoling ceramic barium titanate, up to 9% of the domains reorient by 90°, indicating that during poling at least this percentage of the domains was permanently reoriented by 90°. Ceramic barium titanate shows a strong anelastic effect in the ferroelectric state, presumably due to domain reorientations under stress. Application of tensile and compressive stresses causes up to 13% of the domains to change their orientation by 90°, but, unlike the electric case, no permenent domain reorientation is found. These domain switches are detected by x-ray intensity and strain measurements. The agreement between the percent domain switches computed from the x-ray data and that computed from the strain data is good in the case of mechanical compression, but not in the case of electrical and mechanical tension. In the latter case more domains appear to switch in the bulk than in the surface of the material. A space-charge effect at the surface of ferroelectric barium titanate is suggested as a reason for this anomaly. Experimental evidence of the effect of grinding, etching, and irradiation on the domain orientation in the surface layer of ceramic barium titanate is cited.