Bi(Zn-0.5,Ti-0.5)O-3 (BZT) doped Pb(Zr-0.4,Ti-0.6)O-3 (PZT) films were fabricated using a chemical solution deposition method and were characterized intensively in the present work. It was discovered that the room temperature remnant polarization and zero-field longitudinal piezoelectric constant of the BZT-doped PZT film were enhanced by 23% and 30%, respectively, as compared with those of the undoped PZT film prepared under the same experiment conditions. In order to explain the improved ferroelectric properties, the phase structures of the BZT-PZT and undoped PZT films were experimentally investigated in a broad temperature range (from 30 to 600 degrees C) by using the high temperature two-dimensional X-ray diffraction method. It was found that the improvement in ferroelectricity does not correspond to an elevated Curie temperature (T-C) or a substantially larger tetragonality (c/a). The difference on the change of T-C by doping of Bi-based perovskites in PZT solid solutions between this work and some previous investigations was explained on the basis of Zr/Ti ratio, and the necessity of an in-depth theoretical investigation was addressed. (C) 2012 Elsevier B.V. All rights reserved.