Crystal growth and dielectric properties of new ferroelectric barium titanate:: BaTi2O5

Single crystals of the ferroelectric BaTi2O5 and BaTiO3 were prepared from a solution of 33-mol% BaO and 67-mol% TiO2 by a rapid cooling method. The dielectric constant (epsilon') and dielectric loss tangent (tandelta) were measured in a wide temperature range of 10-860 K and in a frequency range of 0.1-3,000 kHz. The epsilon' along the b-axis of the BaTi2O5 crystal, prepared in air, shows a sharp dielectric anomaly reaching 30,000 at the ferroelectric Curie temperature of T-C = 752 K. By contrast, the crystal prepared in a reducing atmosphere shows a diffuse phase transition near T-C = 703 K. The values of epsilon' and tandelta are compared between these three crystals consisting of two kinds of BaTi2O5 and one BaTiO3.