Effect of particle size on the optical properties of lead zirconate titanate nanopowders

Abstract

Abstract Nanopowder samples of lead zirconate titanate (Pb 1.1 Zr 0.52 Ti 0.48 O 3 or PZT ) were prepared by the sol‐gel method with controlled pH values. The samples were characterized using FTIR spectroscopy, XRD , FE ‐ SEM , and TEM techniques. Most of the peaks in the XRD pattern were related to the coexistence of tetragonal‐rhombohedral phases and confirmed the formation of PZT with a perovskite structure. Also, the crystallite size of PZT nanopowders was in a range of 17‐28 nm. FTIR spectroscopy revealed a longitudinal optical ( LO ) and transverse optical ( TO ) phonon modes corresponding to the stretching vibration of Ti‐O and Zr‐O bonds. The influence of pH values on the LO and TO phonon modes, LO ‐ TO splitting, refractive index n (ω), extinction coefficient k (ω), and the real ɛ 1 (ω) and imaginary ɛ 2 (ω) parts of dielectric function was discussed. These properties were investigated in the mid‐infrared region (450‐750 cm −1 ). The energy loss function Im[−1/(ɛ)] of PZT nanopowders was obtained by Kramers‐Kronig dispersion relations. The TO phonon frequency decreases with increasing crystallite size of the PZT samples. This effect does not happen at pH 8 to pH 9. As the crystallite size increased from 17.26 nm (at pH 5) to 27.25 nm (at pH 7), the LO ‐ TO splitting increased as well. This result showed that the optimum pH for absorption of IR radiation and optical application was at pH 7.