La2O3-doped barium zirconate titanate (Ba1-xLax)Zr0.2Ti0.8-x/4O3 ceramics have been fabricated by conventional solid-state route. The ferroelectric relaxor behavior and dielectric properties of (Ba1-xLaxZr0.2Ti0.8-x/4O3 ceramics have been investigated. La3+ ions substitute for A-site Ba2+ ions to enter the unit cell maintaining the perovskite structure of solid solution and induce the occurrence of ferroelectric relaxor behavior. The temperature dependence dielectric constant and loss reveals that (Ba1-xLax)Zr0.2Ti0.8-x/4O3 ceramics have a typical relaxor behavior and diffuse phase transition characteristics and the degree of ferroelectric relaxation behavior is enhanced with the increase of La-dopant concentration. The Curie temperature (T-C) of (Ba1-xLax)Zr0.2Ti0.8-x/4O3 ceramics is remarkably shifted to lower temperature with the increase of x. The dielectric loss of (Ba1-xLax)Zr0.2Ti0.8-x/4O3 ceramics is obviously improved by La-doping. The appropriate La2O3 doped barium zirconate titanate ceramics with suitable dielectric constant, low dielectric loss and high tunability could be attractive materials for tunable ceramic capacitors and tunable microwave device applications. (c) 2007 Elsevier B.V. All rights reserved.