Dielectric properties of (010) oriented polycrystalline Ta ₂O₅ substituted BaTi₂O₅ prepared by arc melting

Ta₂O₅ substituted polycrystalline BaTi ₂O₅ (BT₂T) was prepared from the raw materials of BaCO₃, TiO₂ and Ta₂O₅ by arc melting on a water-cooled copper plate in the nominal composition of Ba (Ti _1-1.25yTa_y)₂O₅ (y = 0 to 0.050). At y < 0.050, the main phase of the obtained specimens was BT₂T which crystallized in a monoclinic cell with (010) orientation perpendicular to the copper plate. The a-axis length and ß angle increased from 1.6895 to 1.6916 nm and 103.11° to 103.20°, respectively, and then became almost constant with increasing y from 0 to 0.050. The b- and c-axes lengths were almost constant of 0.3934 and 0.9411 nm, respectively. A peak was observed in the temperature dependence of permittivity for all specimens. The Curie temperature shifted from 750 to 300 K with increasing y from 0 to 0.050. The permittivity of the specimen prepared at y= 0.0025 showed the highest value of 3800 at 707 K. Relaxor-like behaviors were observed for the specimens prepared at y> 0.025.