The effect of dc electric field and temperature on dielectric properties of sol-gel derived (Ba0.65Sr0.35)TiO3 (BST35) ceramics were investigated. It is observed that the phase transition of BST35 sample is a weak diffusion phase transition. The value of gamma characterizing the degree of diffuse transition is 1.46, 1.49, 1.53 and 1.51, respectively for BST35 sample measured at frequency of 100 Hz, 1 kHz, 10 kHz and 100 kHz. The results indicate that the nonlinear dielectric properties for the BST35 ceramics at room temperature is expected to be very strong. The permittivity become very high and the polarization that can be induced by even a small field can be quite large at temperature near to the transition temperature. The loss tangent values were decreased significantly at temperatures above the transition temperature. The dielectric constant was greatly suppressed under dc electric field. At room temperature (293 K) and 20 kV cm(-1), the tunability (k) and figure of merit (FOM) were 60% and 60. (c) 2008 Elsevier B.V. All rights reserved.