Synthesis and Raman investigation of sol-gel-derived relaxor ferroelectric thin films

Pb(Fe2/3W1/3)O-3 (PFW) thin films were deposited on platinized silicon substrate by a chemical solution deposition technique. Room-temperature X-ray diffraction (XRD) revealed a pure cubic crystal structure of the investigated material. The microstructure indicated good homogeneity and density of the thin films. A Raman spectroscopic study was carried out on PFW to study the polar nano-regions in the temperature range 85-300 K. The Raman spectra showed a change in the peak intensity and a shift towards the lower wavenumber side with temperature. The Raman spectra also revealed the transition from the relaxor to the paraelectric state of PFW. There was no evidence of a soft mode in the low-temperature region, in contrast to the normal ferroelectric behavior. The polar nano-regions tend to grow and join at low temperatures (similar to 85 K), which become smaller with increase in temperature. The presence of strong Raman spectra in the cubic phase of the material is due to the presence of distributed Fm3m (Z = 2) symmetry nano-ordered regions in the Pm3m (Z = 1) cubic phase. Copyright (c) 2007 John Wiley & Sons, Ltd.