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Concentration of oxide ion vacancies and its ordering in crystalline lattices play an important role in the structural, optical and ionic transport properties of RE2O3–MO2 (RE (Rare earths), M = Ti, Zr, Hf) systems. Rarely investigated rare earth zirconate system, RE4Zr3O12 (RE = Dy, Y, Er, and Yb) exhibiting the polymorphic structural forms, was chosen for the present study. RE4Zr3O12 nanoceramics were prepared through an auto-ignited combustion method; thereafter, dense bulk ceramics were derived from them at relatively low temperatures. X-ray diffraction studies carried out on the nanoceramics as well as bulk ceramics suggest defect fluorite structure for RE = Dy, Y and Er whereas δ-phase rhombohedral structure for RE = Yb ceramics. Extent of oxide ion ordering and the structural variations due to the replacement of rare earth ions in the crystalline lattices were analyzed by Raman and infrared spectroscopy. UV–Visible and photoluminescence spectroscopy were employed to investigate the optical properties of the nanoceramics. Impedance spectroscopic studies carried out on the bulk ceramic materials show that the oxide ion hopping conduction mechanism in the bulk ceramics was affected by the structural factors and free mobile oxide ion concentration. Increase of total electrical conductivity of the dense ceramics with the increase of temperature was in accordance with the Arrhenius relation. Electrical conductivity of fluorites was higher than the δ-phase ceramics, which was attributed to the decreased activation energy and increased available number of mobile oxide ions in the fluorite structure.

The influence of laser fluence on the properties of thin films of tantalum oxide is studied in this paper, varying the laser fluence from 5.7 to 8.3 J/cm2. Thin films of tantalum oxide were deposited on glass substrates using pulsed-laser ablation technique. X-ray diffraction studies confirm the amorphous/nanocrystalline nature of all the films irrespective of the laser fluence. The Tauc plot analysis suggests that tantalum oxide is an indirect band gap material, whose band gap decreases with increase in laser fluence. The refractive index of the films is found to decrease with increase in laser fluence but the extinction coefficient of the films increases with increase in laser fluence. Fourier transform infrared studies suggest the use of tantalum oxide thin films as oxygen sensors. Micro-Raman analysis reveals the sensitiveness of Ta-O-Ta and Ta-O vibration modes to laser fluence. Among all the films, the film deposited at a laser fluence of 7 J/cm2 is found to be superior in quality.

CdO doped (doping concentration 0, 1, 3 and 16 wt%) ZnO nanostructured thin films are grown on quartz substrate by pulsed laser deposition and the films are annealed at temperature 500 °C. The structural, morphological and optical properties of the annealed films are systematically studied using grazing incidence X-ray diffraction (GIXRD), energy dispersive X-ray analysis (EDX), scanning electron microscopy (SEM), atomic force microscopy (AFM), Micro-Raman spectra, UV–vis spectroscopy, photoluminescence spectra and open aperture z-scan. 1 wt% CdO doped ZnO films are annealed at different temperatures viz., 300, 400, 500, 600, 700 and 800 °C and the structural and optical properties of these films are also investigated. The XRD patterns suggest a hexagonal wurtzite structure for the films. The crystallite size, lattice constants, stress and lattice strain in the films are calculated. The presence of high-frequency E2 mode and the longitudinal optical A1 (LO) modes in the Raman spectra confirms the hexagonal wurtzite structure for the films. The presence of CdO in the doped films is confirmed from the EDX spectrum. SEM and AFM micrographs show that the films are uniform and the crystallites are in the nano-dimension. AFM picture suggests a porous network structure for 3% CdO doped film. The porosity and refractive indices of the films are calculated from the transmittance and reflectance spectra. Optical band gap energy is found to decrease in the CdO doped films as the CdO doping concentration increases. The PL spectra show emissions corresponding to the near band edge (NBE) ultra violet emission and deep level emission in the visible region. The 16CdZnO film shows an intense deep green PL emission. Non-linear optical measurements using the z-scan technique indicate that the saturable absorption (SA) behavior exhibited by undoped ZnO under green light excitation (532 nm) can be changed to reverse saturable absorption (RSA) with CdO doping. From numerical simulations the saturation intensity (Is) and the effective two-photon absorption coefficient (β) are calculated for the undoped and CdO doped ZnO films.

5% SnO 2 doped tantalum oxide (Ta 2 O 5 ) films are deposited on quartz substrates at different substrate temperatures of 300 K, 773 K, 873 K and 973 K using pulsed laser deposition in an oxygen ambient of 0.002 mbar. Undoped Ta 2 O 5 films are also deposited on quartz substrates kept at substrate temperature 973 K under the same oxygen ambient using PLD. The films are characterized using GIXRD, AFM, FTIR, micro-Raman and UV-visible spectroscopy. Undoped films show an amorphous nature even at a substrate temperature of 973 K, whereas, SnO 2 doped films show crystalline nature even for deposition at 300 K. As far as our knowledge goes, this is the first report of crystalline Ta 2 O 5 films deposited at room temperature. The average size of the crystallites calculated using the Debye-Scherrer formula, shows that the size of the crystallite decreases with increase in substrate temperature. FTIR and micro-Raman spectroscopic analysis reveals the presence of Ta-O-Ta, O-Ta and O-Ta-O vibrational bands in the films. Raman analysis indicates that the addition of SnO 2 suppresses the bond formation and changes the magnitude of bonds in Ta 2 O 5 . AFM patterns reveal the formation of Ta 2 O 5 nanorods of diameter about 100 nm for the doped film deposited at 973 K. Optical transmittance of the films is found to be sensitive to substrate temperature as well as to the presence of SnO 2 . A blue shift in the band-gap of the doped films is observed. The decrease of band-gap with decrease of particle size observed for SnO 2 doped films can be due to a band-bending effect. The transmittance of the films is found to depend on SnO 2 doping and substrate temperature.

Thin films of tantalum oxide (Ta 2 O 5 ) have been prepared by pulsed laser deposition technique at different substrate temperatures (300–973 K) under vacuum and under oxygen background (pO 2 = 2 × 10 −3 mbar) conditions. The films are annealed at a temperature of 1173 K. The as-deposited films are amorphous irrespective of the substrate temperature. XRD patterns show that on annealing, the films get crystallized in orthorhombic phase of tantalum pentoxide (β-Ta 2 O 5 ). The annealed films deposited at substrate temperatures 300 K and 673 K have a preferred orientation along (0 0 1) plane, whereas the films deposited at substrate temperatures above 673 K show a preferred orientation along (2 0 0) crystal plane. The deposited films are characterized using techniques such as grazing incidence X-ray diffraction (GIXRD), atomic force microscopy (AFM), micro-Raman spectroscopy, Fourier transform infrared (FTIR) spectroscopy and UV–visible spectroscopy. FTIR and micro-Raman measurements confirm the presence of Ta–O, Ta–O–Ta and O–Ta–O bands in the films. Grain size calculations from X-ray diffraction and AFM show a decrease with increase in substrate temperature. The variation of transmittance and band gap with film growth parameters are also discussed.