Microstructure and phase development during the thermal decomposition of sol-gel precursor coatings of PbZr0.53Ti0.47O3 on platinized silicon substrates have been investigated for a triol sol-gel route. The single-layer, 0.4 mum PZT films were heated from below the substrate, over the temperature range 350-600degreesC, using a calibrated hot plate. The first crystalline phase to appear was a PbPt3 intermetallic phase at the Pt/PZT interface. Although perovskite PZT formed at ca. 500degreesC, heating at higher temperatures, for example 550degreesC for 30 min, was required to develop ferroelectric hysteresis loops. However, the rather low value of remanent polarization, P-r = 11 muC(.)cm(-2), was consistent with incomplete crystallization at 550degreesC. The values of remanent polarization increased with increasing processing temperatures, reaching 21 muC(.)cm(-2) for samples heated at 600degreesC, with a corresponding E. value of 57 kV(.)cm(-1). Distinctive spherical precipitates up to ca. 50 nm in size have been identified by TEM in the lower portions of otherwise amorphous coatings, after heating at around 350-400degreesC. Although their precise composition could not be identified, they were mostly Pb-rich, and it is speculated that they form due to reduction of some of the lead(H) acetate starting reagent, to atomic Pb during the early stages of thermal decomposition of the organic components of the gel; it is possible that subsequent reactions occur to form lead oxides or carbonates. High levels of porosity were present in many of the fully crystallized films. The possible reasons for this are discussed.