Abstract Cobalt substituted zinc ferrite aluminate series with compositional formula Zn 1‐ x Co x FeAlO 4 ( x  = 0.0, 0.2, 0.4, and 0.6) is prepared by chemical sol–gel synthesis. The prepared samples are characterized by X‐ray diffraction (XRD), transmission electron microscope (TEM) technique. A cubic spinel phase is revealed by XRD analysis and confirmed from selected area electron diffraction (SAED) pattern. The true values of lattice constant are obtained from Nelson–Riley extrapolation plot, and lattice strain values are obtained with the help of Williamson‐Hall equation. The TEM image confirms average crystallite size of 31 nm. The dielectric study discloses the decrease of dielectric constant and loss tangent with the increasing frequency of applied field.