Size Effect of Nanograined BaTiO3 Ceramics Fabricated by Aerosol Deposition Method

We demonstrated the size effect of nanograined BaTiO 3 ceramics using freestanding BaTiO 3 thick films fabricated by the aerosol deposition (AD) method. Dense BaTiO 3 thick films fabricated by the AD method were crystallized and detached from the SrTiO 3 substrate by annealing treatment at 600 \mbox{ \circ C}, and then the grain size was controlled by reannealing treatment at various temperatures. As a result, freestanding BaTiO 3 thick films with various grain sizes from 24 to 170 nm were successfully obtained. Polarization--electric field ($P$--$E$) measurement revealed that BaTiO 3 ceramics with grain sizes of more than 58 nm showed ferroelectricity, whereas BaTiO 3 ceramics with an average grain size of 24 nm showed paraelectricity at room temperature. Dielectric measurement indicated that the permittivity decreased with decreasing grain size in the range from 170 to 24 nm. The decrease in permittivity was due to the decreases in ferroelectricity and domain-wall contributions with decreasing grain size.