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LiNbO 3 thin films were deposited by means of Al:ZnO as intermediate layer using pulsed laser deposition and their structural, linear and nonlinear optical (NLO) properties were investigated. The films were found to be polycrystalline, (110) orientation for Al:ZnO/fused silica and (300) orientation for Al:ZnO/quartz substrates. The films demonstrated a transparency of >80% in the visible and near-infrared region. The NLO studies were performed with the Z-scan technique using ∼150 fs, 80 MHz pulses at 800 nm. The studies revealed that the polycrystalline LiNbO 3 films and (300) LiNbO 3 films demonstrated reverse saturable absorption while a transition to saturable absorption was observed in the case of (110) LiNbO 3 . The presence of two-photon absorption is attributed to the indirect transition via intermediate defect levels which is related to the structural asymmetry. The large nonlinearity in refractive index could be a result of the strain induced ferroelectric polarization. The magnitude of the third order optical nonlinearity of all films was ∼10 −11 e.s.u. which is orders of magnitude higher than the value obtained for single crystal Z-cut LiNbO 3 .

Different shapes of (Zr0.8Sn0.2)TiO4 dielectric resonators were prepared through a slurry based route involving organic/inorganic carrier medium. In the present work, the ceramic powder is dispersed in a water based carrier with monomer and cross linker as binder system in order to get the stable highly solid loaded slurry. This slurry is casted in to an inexpensive polyethylene mould of desired shape to form net shaped dielectric resonators. The de-molded samples are subjected for further heat-treatments. (Zr0.8Sn0.2)TiO4 ceramics sintered at 1400 °C exhibited desirable microwave dielectric properties of єr=37, Qxf=32,000 and τf=+6 ppm/°C.

Insulator–conductor composites are touted as excellent materials for charge storage capacitor applications. Cupric oxide (CuO) decked few-layered graphene (FLG) can be one such composite. Understanding the dielectric behaviour of CuO–graphene system, which is anticipated to be intricate, is definitely an attention-grabbing one. Here, CuO decked FLG composite is synthesized using molecular level mixing. Samples with different amounts of FLG (low and high amount FLG containing samples are named as CuO-0.1G and CuO-0.2G, respectively) are prepared. At 1 kHz, dielectric permittivity ( e 1 ) values of CuO-0.1G ( e 1 = 318) and CuO-0.2G ( e 1 = 667) are ∼1.1 and ∼2.3 times greater, respectively than that of CuO ( e 1 = 289). Increase in e 1 is ascribed to the formation of continuous conductive pathway between CuO decked FLG sheets. AC conductivity ( σ ) of CuO-0.1G and CuO-0.2G samples is found to increase with applied frequency and follows Jonscher’s power law. Experimental data pertaining to AC conductivity could be easily fitted to quantum mechanical tunnelling model. The fitting results suggest electron hopping mechanism as the cause for enhanced AC conductivity. This work gives a great motivation to develop composite materials (with conducting and insulating constituents) whose dielectric behaviour can be controlled by mechanisms occurring at atomistic scale.

Mono phase LiNb3O8 (LN), a compound that comes during the processing of LiNbO3 is synthesized as thin films using sol gel process followed by microwave annealing. Initial studies like phase determination, structure and microstructure of this particular compound are done. XRD pattern confirmed LN as monoclinic with no preferred orientation. From Raman spectroscopy, we found that crystallization is not uniform and new peaks are appearing. Untraceable phases have been identified from Raman imaging. The broadening of peak width is increasing with increase in temperature. Low frequency modes are due to the Li deficiency sites occupied by Nb ions and higher frequency peaks are due to oxygen displacement. Non stoichiometric phases can be identified from color contrast in Raman imaging. Microwave annealing is a successful method to obtain LiNb3O8 thin films. Copyright © 2014 VBRI press.

Nanoindentation technique has been used to determine the mechanical properties of bismuth layered structure ferroelectric thin films, which have been shown to be promising for MEMS based devices used in sensing, actuation and energy harvesting, especially at elevated temperatures. SBTi (SrBi4Ti4O15) is a promising layered ferroelectric material and thin films of this composition are deposited on amorphous fused silica substrates by rf sputtering technique varying the substrate temperature from 600-725oC. The crystal structure and surface morphology of SBTi thin films are characterized by X-ray diffraction and atomic force microscopy. Depth- sensing nanoindentation system is used to measure the mechanical characteristics of SBTi thin films. Nanoindentation measurements reveal that the Young's modulus and hardness of SBTi thin films are related with grain size and crystal orientation which in turn depend on substrate temperature. The increase in mechanical properties with grain size is observed, indicating the reverse Hall-Petch effect. Furthermore, hardness and Young's modulus of the (119) oriented films were higher than those of (0010) oriented films. The tribological properties of these films are confirmed by performing the scratch tests on the same films. Copyright © 2014 VBRI press.

Sc2O3 and Lu2O3 doped LiNbO3 polycrystalline ceramics were prepared by the solid state reaction method. Structural, morphological and luminescence properties have been studied by X-ray diffraction, Raman spectroscopy, FE-SEM and Flurospectrometery respectively. From XRD, no structural changes have been observed in Sc2O3 and Lu2O3 doped LiNbO3. SEM images show clear and distinct grains. Strong violet luminescence at 414 nm and 435 nm were observed for all samples with excitation in UV region (370 nm). Apart from this, with excitation at 289 nm, blue emission at 473 nm in pure LiNbO3 is observed. With change in Sc2O3 dopant concentration, this peak is red shifted to 505 nm and 525 nm exhibiting green emission. Changes observed in Raman modes strongly support Stokes shift in luminescence peaks. Sc2O3 and Lu2O3 doped LiNbO3 can be used as an efficient luminescent material in violet, blue and green region under UV excitation.

Lithium niobate (LiNbO3) thin films were prepared using pulsed laser deposition technique. Structural properties of the same were examined from XRD and optical band gap of the thin films were measured from transmittance spectra recorded using UV-Visible spectrophotometer. Nonlinear optical properties of the thin films were recorded using Z-Scan technique. The films were exhibiting third order nonlinearity and their corresponding two photon absorption, nonlinear refractive index, real and imaginary part of nonlinear susceptibility were calculated from open aperture and closed aperture transmission curves. From these studies, it suggests that these films have potential applications in nonlinear optical devices.

Lithium triniobate (LiNb3O8) has been prepared using microwave assisted combustion synthesis at a low temperature of 400 °C. Graphite oxide is synthesized using Hummers method and thereafter it is thermally exfoliated at 500 and 700 °C to obtain two samples of Few Layered Graphene (FLG). Then, FLG-LiNb3O8 composites prepared through a simple ultra-sonication assisted solution mixing process. The obtained samples are named as FLN5 and FLN7 based on the temperature used to obtain FLG. Low frequency dielectric measurements are recorded for both the samples and the measured dielectric constant is observed to be more for FLN5 (250 at 60 Hz) than FLN7 (115 at 60 Hz) whilst the dielectric loss is less in case of FLN5 (1.525 at 60 Hz). The enhancement in dielectric properties for FLN5 is explained in terms of polarization in FLG-LiNb3O8 composites.