The formation mechanism of the novel core-shell microstructure in polyvinyl alcohol-additive lead zirconate titanate films

Crack-free lead zirconate titanate (PZT) films were fabricated by the sol-gel process using a modified polyvinyl alcohol (PVA) solution, which contained PVA, glycerol, and water. In this study, the modified PVA solution was added to the PZT precursor solution, ranging from 1:2 to 1:6 in weight ratio. The X-ray diffraction results showed that the addition of the PVA solution still made the PVA-additive PZT films maintain crystallinity at 600°C for 30 min. The phase transformation of the PVA-additive PZT films was similar to the PVA-free PZT films, but the initial formation temperature of the perovskite phase was successfully reduced to 500°C by the enhancement of the PVA solution. Furthermore, the chelating effects of PVA induced to have the novel circular PZT clusters with a lead-rich core, and a zirconium- and titanium-rich shell. The formation mechanism of the novel core-shell PZT films is discussed. The circular core-shell PZT clusters acted as heterogeneous nucleation sites to reduce the nucleation barrier. Therefore, the PVA-additive multi-layer PZT films showed a smaller grain size than PVA-free PZT films. With this innovative procedure, crack-free, fine-grained, multi-layer PZT films were successfully obtained.