Dielectric Properties and Crystal Structure of Barium Titanate Fine Particles

Abstract

Fine particles of high-purity barium titanate from a minimum of 500A upwards were prepared. by the thermal decomposition of barium titanyl oxalates, BaTiO(C₂O₄) ₂⋅4H₂0, at 600-1100°C. The effective dielectric constant was measured with the particles dispersed in Araldite resin. The following results are of interest: (1) In the case of fine particles of 500-700A, the effective dielectric constant delineates a smooth curve with temperature and the ferroelectric Curie peak moves to low temperature. (2) From X-ray diffraction analysis, the tetragonality decreased with decreasing particle size, thus leading to cubic symmetry.
A brief discussion was given to the correlation between the decrease in tetragonality and the shift of the Curie point.