Thermal Behaviour of Compositions in the Systems × BaTiO₃ + (1-x) Ba(Ln_0.5B_0.5)O₃

Abstract

The effect of temperature on the dielectric constant (ε), tan 6 (loss tangent) and the ferroelectric properties of compositions in the systems x BaTiO₃ + (1-x) Ba(Ln_0.5B_0.5)O₃ (O≤x≤1, Ln³⁺ = a rare earth cation and Y³⁺, B⁵⁺ = Ta,Nb,V) reveal that in the Ta⁵⁺ system at x = 0.8, the ε_max (ε at T_c) and T_c (the Curie-point) exhibit an increasing trendwith decreasing ionic radii of the In³⁺ ions, whereas in the analogous Nb⁵⁺ system, an almost linear behaviour has been observed. In the V system, the pure phases (x = O) exhibit increasing trend of ε_max and T values with de- creasing rare earth cation size. Phases with x = 0.8, exhibit a break at Nd³⁺ in ε_max values, in contrast to an increasing trend in T_c values with decreasing rare earth cation size, Similar behaviour is observed for the polarization data. The increasing trend in the T_c values in the direction Ta⁵⁺ -Nb⁵⁺-V⁵⁺ at x = 0.8 is perhaps reminiscent of the nephelauxetic effect.

The T_C values for these first order transitions have been confirmed by recording DTA curves against inert αAl₂O₃, the enthalpy change, however, being appreciably bow in the present series.