Crystallization of monodisperse lead zirconate titanate nanoparticles produced by laser ablation

Monodisperse lead zirconate titanat̀e (PZT) nanoparticles with diameters of 9 nm were produced by laser ablation followed by a gas-phase thermal treatment in combination with a size-classification technique using a very low-pressure differential mobility analyzer. The particles prior to the thermal treatment are amorphous. When the laser power density for ablation increases from 0.5GW/cm² to 12GW/cm², the production yield of the particles increases regardless of the laser photon energy. When the laser photon energy is 3.5 eV, the nanoparticles generated with laser power densities as high as 7 GW/cm² are crystallized to perovskite by thermal treatment at 900°C, while those generated with even, higher power densities become pyrochlore. In contrast, when the laser photon energy is 2.3 eV, perovskite nanoparticles are obtained only at a power density of 0.5 GW/cm². These results reveal that the crystalline structure of PZT nanoparticles can be adjusted to perovskite or pyrochlore by changing thermal treatment temperature, laser power density, and photon energy. Furthermore, X-ray photoelectron spectroscopy indicates that the crystallization to pyrochlore is caused by lead deficiency.