Effect of Crystallite Size on the Ferroelectric Domain Growth of Ultrafine BaTiO3 Powders

Abstract

The relationship between ferroelectric domain growth and the size of crystallites in ultrafine BaTiO 3 powders has been investigated. It was observed that the critical size for the c → t-BaTiO 3 phase transformation was about 30 nm and that BaTiO 3 crystallites probably transformed from single-domain to multidomain when the particle size was larger than 100 nm. X-ray diffraction patterns of BaTiO 3 /PVDF composites before and after poling indicated that the degree of poling efficiency for composites with fine BaTiO 3 powders is much smaller than for coarser powders larger than 100 nm. The present work indicates that the presence of ferroelectric domains in BaTiO 3 powder depends on the constraining force introduced by hard agglomeration of the crystallites. The particles obtained by calcining at a higher temperature (larger than 100 nm and partially sintered), composed of several crystallites, may behave similar to grains in fine-grained BaTiO 3 ceramics where ferroelectric domains are generated due to mechanical clamping. On the other hand, particles of small size composed of single crystallite and without clamping force, may deform similar to a lattice cell and avoid formation of twins.