Particle Formation During Spray Pyrolysis of Lead Zirconate Titanate

A twin-fluid atomization spray pyrolysis technique has been used to produce lead zirconate titanate (PZT) powders from a sol–gel precursor solution. Samples were removed from ports sited along the reactor in order to examine particle development at progressive stages of pyrolysis. The total time in the reactor was 2.6 s. The size and shape of the particles showed no change between the first port (190°C) and the hottest part of the reactor (820°C), indicating that the physical structure of the particles was established during the initial drying stages. The powders were mainly composed of spherical particles, but irregular forms were also present, which were thought to result from the inward collapse of hollow gelatinous particles. Crystallization of PZT commenced at around 700°C, initially to a pyrochlore or fluorite intermediate phase, with the desired perovskite phase developing between 790°C and 815°C. However, a minor amount of the pyrochlore/fluorite phase persisted in the final powder. The final powders also contained basic lead carbonate, 2PbCO₃·Pb(OH)₂, which existed in the form of elongated crystallites on the surface of the PZT particles.