Modern flexible and sensitive sensors based on polymer–ceramic composites employ lead zirconate titanate (PZT) granulates having the morphotropic phase boundary (MPB) composition as the piezo active ingredient, as this composition gives the best properties in fully ceramic piezoelectric sensors. In this study, the possibility of using PZT granulates with compositions, which are not in the MPB region of the PZT phase diagram was investigated. Random 0–3 PZT–epoxy composites were prepared for the complete composition range of PZT ceramics [Pb(ZrxTi(1-x))0.99Nb0.01O3] with x ranging from x = 0 to x = 0.80. Piezoelectric and dielectric properties of such composites were systematically studied. It is shown that the highest voltage sensitivity (i.e. g33) of the piezoelectric composites is obtained for composition with much lower Zr levels (x < 0.1) than the MPB composition. The shift in optimal composition is related to shift in dielectric constant of PZT as a function of the Zr concentration.