K 0.5 Na 0.5 )NbO 3 (KNN) thin films have been deposited onto Pt/Ti/SiO 2 /Si and quartz substrates by RF magnetron sputtering. The films were deposited at 400°C with the variation in oxygen mixing percentage (OMP) ratio from 0% to 100% and annealed at 700°C in oxygen atmosphere. The crystallinity of the films is found to be increased with increased OMP. Dielectric properties of the films were examined over the frequency range from 1 kHz to 1 MHz and the temperature range of 30°C to 400°C. The Curie temperature of the films was found to be in the range 369°C-373°C. For the first time, the split postdielectric resonator (SPDR) method was used to measure the microwave (10-20 GHz) dielectric properties of KNN thin films. The optical properties of as-deposited and annealed KNN thin films were investigated by means of transmittance spectra. The optical bandgap is calculated by using the Tauc relation, and found to be in the range 4.34-4.40 eV and 4.29-4.37 eV for the as-deposited and annealed films, respectively. The refractive index (n 700nm ) of the films found to be in the range 1.98-2.01 and 1.99-2.07 for as-deposited and annealed films, respectively. The refractive index dispersion is analyzed by using Wemple-DiDomenico (W-D) single-oscillator model. The effect of annealing and OMP on the refractive index, packing density and W-D parameters has been investigated. The average single oscillator energy (E o ) and dispersion energies (E d ) of the annealed KNN thin films are in the range of 6.17-7.16 eV and 18.77-22.19 eV, respectively. AC-conductivity of the annealed films was analyzed by using double power law. Ag/KNN/Pt thin films followed the ohmic conduction (J / E a , where a~1) and the low leakage current density obtained for the deposited at 100% O 2 is 3.14 3 10 -5 A/cm 2 at 50 kV/cm. J. Jones-contributing editor Manuscript No. 35693.

We report bioceramic composites of varying concentrations of Ba 0.5 Sr 0.5 TiO 3 (BST) and Ca 10 (PO 4 ) 6 (OH) 2 (HAP) for the analysis of electrical properties. The motivation is to predict the suitability of the composites for bio-electrets or the practical possibility in designing electro-active scaffolds. X-ray diffraction (XRD) and field-emission scanning electron microscopy (FESEM) are used to analyze the microstructural evolution of the composites. A systematic variation in the grain and crystallite sizes is noticed from the FESEM and XRD, along with the presence of Sr 5 (PO 4 ) 3 (OH) (SAP). The temperature and frequency variations of the dielectric properties of the composites are studied. Modeling of the dielectric properties with the microstructural properties and at. % of the monolith BST is presented. Cole−Cole formalism is adopted to model the electrical behavior of the synthesized composites. Furthermore, the ac conductivity analysis reveals that Mott's variable range hopping (VRH) conduction is the most appropriate formalism that successfully describes the conduction process. The established Mott's VRH is also related to the polarization mechanisms active in the specimens. Our study projects a correlation between the electrical and biological properties by predicting the protein adsorption behavior from the perspective of impedance spectroscopy.

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Nanoparticles of (Zr0.8Sn0.2)TiO4 (ZST) ceramics were prepared by ball milling. Different concentrations of (1, 2 and 3 wt%) nanoparticles of size about 60 nm were introduced into the sub micron‐sized (0.8 μm) powder of the ZST ceramics to study the effect of their inclusion on densification, microstructure, and microwave dielectric properties of the ZST ceramics. It is found that the addition of nanoparticles to the ZST ceramics significantly improved the density with reduction in sintering temperature. In the present case, it is believed that the surface energy of fine powders and their defect energy are the driving force for sintering and increase in uniform grain size, which are activated at the sintering temperature. The microwave dielectric properties of ZST ceramics were also heavily influenced by the addition of nanoparticles of ZST. The maximum dielectric constant of 39.2 and Q × fo value of 72 900 were found to be for the samples added with 2 wt% of the nanoparticles and sintered at 1300°C for 3 h. However, it is observed that samples made with nanopowder alone exhibited poor sinterability.