Investigation of physical properties of perovskite PZT thin films as a function of sol temperature

PZT [Pb (Zr_0.52Ti_0.48)O₃] thin films were prepared on quartz substrate by sol gel spin coating technique. The Zr/Ti ratio was kept at 52/48 which is morphotropic phase boundary (MPB). At MPB both tetragonal and rhombohedral phases coexist and greatly influence the physical properties. In this work the PZT thin films were coated with sol kept at room temperature and at 125 °C as 3 (SQ1) and 2 (SQ2) layers. The structural, morphological, compositional and optical properties of coated thin films were studied using X-ray diffraction, scanning electron microscopy (SEM) and UV–Visible spectroscopy. The X-ray diffraction patterns reveal perovskite phase formation for both the films annealed to 660 °C. The micro structural parameters such as lattice constant, crystallite size, dislocation density and strain were determined. The grain size increases with increase in sol temperature from 24 to 27 nm. The SEM analysis indicates dense structure of films with good adhesion to the substrate. The cross sectional view of the films provides the thickness of films as 760 and 955 nm. The EDAX data gives the composition of the films. Optical spectra indicate that the films have direct band transitions. The band gap values were dependent on crystallite size and strain. As thickness increases the band gap value decreases from 3.73 to 3.26 eV.