Temperature dependence of optical and structural properties of ferroelectric B3.15Nd0.85Ti3O12 thin film derived by sol-gel process

We report the annealing temperature dependence of optical properties in ferroelectric B3.15Nd0.85Ti3O12 (BNdT) thin film for the first time. BNdT thin films are prepared by a sol-gel/spin coating method. Structural properties of BNdT thin films upon different thickness and annealing temperatures are characterized using the X-ray diffraction, scanning electron microscopy, atomic force microscopy, and transmission electron microscopy. The BNdT thin film annealed at 650 degrees C exhibits a well defined perovskite crystalline structure with high c-axis orientation, which leads to a saturated polarization-electric field (PE) hysteresis with a remanent polarization of 2P(r) = 39.6 mu C/cm(2) and coercive field of 85 kV/cm at 5 V. Little fatigue degradation (<5%) is demonstrated upon 1 x 10(10) switching cycles indicating a good fatigue endurance. Additionally, a superior optical transparency T(lambda) of >80% is observed for wavelengths from 250 to 2,000 nm. Fundamental optical parameters of BNdT material such as refractive index n, extinction coefficient k, and band gap energy E-g are extracted from an ellipsometry measurement. Microstructure and annealing temperature dependence of T(lambda), n, k, and E-g variation are also investigated and explained in detail.