BaBi4Ti4-xZrxO15 with x = 0.1. 0.2, 0.3 and 0.5, has been synthesized via modified solid state reaction route. X-ray diffraction studies confirmed the formation of single phase Zr4+ substituted BaBi4Ti4O15 UP to x = 0.2. ZrO2 and Bi2O3 based impurity phases were found at x = 0.3 and 0.5 substitutions. However, Rietveld refinement showed the increase in lattice parameters of BaBi4Ti4O15 up to x = 0.5 substitutions. A broad dielectric peak associated with frequency dependence dielectric maximum temperature was observed at low substitutions. Relaxor behavior was suppressed at x = 0.5 substitution. A broadening and shifting of permittivity-temperature peak was found for the substitution. The high temperature slopes of dielectric peaks were analyzed by quadratic law for relaxors. The degree of relaxation and phase transformation diffusiveness were investigated at different substitutions. (C) 2009 Elsevier B.V. All rights reserved.