Potassium-sodium niobate lead-free piezoelectric materials: past, present, and future of phase boundaries.

Small-sized ZnO rods with an average length of ca. 180 nm and a diameter of ca. 16 nm were successfully associated to reduced graphene oxide (rGO) via a solvothermal reaction conducted in ethanol. A set of characterization including TEM, SEM, XRD, BET, Raman spectroscopy and UV–vis absorption confirm that the ZnO/rGO composite is composed of highly dispersed ZnO rods bound to rGO nanosheets. The photocatalytic activity of the ZnO/rGO composite was investigated under solar light and under visible light irradiation using the Orange II dye in aqueous solution. Results indicate that the ZnO/rGO composite containing 10 wt% rGO used under solar light irradiation exhibit the highest photocatalytic activity and that the kinetic of reduction is of pseudo-fist-order. The photocatalyst is only weakly sensitive to pH changes and to the presence of inorganic salts or to glucose in the reaction medium. In addition, the reusability of the ZnO/rGO composite was studied and the results demonstrate that the photocatalyst can be reused up to fifteen times with nearly negligible loss of activity. The high photocatalytic performances can be attributed to the high specific surface of ZnO rods, to the enhanced visible light absorption of the ZnO/rGO composite and to the strong decrease of charge carrier recombinations originating from the association of ZnO rods with rGO.

ZnO rods/reduced graphene oxide composites prepared via a solvothermal reaction for efficient sunlight-driven photocatalysis

Strategies to achieve high performance piezoelectric nanogenerators

Piezoelectric energy harvesters for biomedical applications

Ce-doped ZnO nanoparticles for efficient photocatalytic degradation of direct red-23 dye

Synthesis and enhanced properties of cerium doped ZnO nanorods

Single crystals of 0.01 and 0.02 mol% crystal violet dye doped triglycine sulfate (NH2CH2COOH)3·H2SO4 (TGS) have been grown by a slow evaporation technique. Enhanced dielectric, optical, thermal and mechanical properties have been achieved by dye doping. Monoclinic structures showing particular coloring patterns and morphology change with dye concentration were obtained. Various functional groups and dye incorporation in the grown crystals were confirmed qualitatively by FTIR and Raman analysis. A significant increase in Curie temperature from 50 to 55 °C with a decrease in maximum permittivity has been observed. The UV-vis spectra showed an increased transmittance window and an increased optical band gap from 5.61 to 6.11 eV as a result of doping. An increase in the sharpness and intensity of the photoluminescence peak with a blue shift has been observed in doped crystals. The thermal stability and the decomposition temperature were found to increase by about 10 °C in 0.01 mol% dye doped TGS. The mechanical strength of the grown crystals was estimated by the Vickers microhardness test and was found to be high for dye doped TGS. A high piezoelectric charge coefficient d33 of 16 pC N−1 was observed for pure TGS which decreased as a result of the dye effect. The fabrication of a patch antenna was carried out after simulating its resonant frequency, making it suitable for telecommunication applications.

Performance of crystal violet doped triglycine sulfate single crystals for optical and communication applications

Enhanced optical, dielectric and piezoelectric behavior in dye doped zinc tris-thiourea sulphate (ZTS) single crystals

Synthesis of 0.64Pb(Mg1/3Nb2/3)O3–0.36PbTiO3 ceramic near morphotropic phase boundary for high performance piezoelectric, ferroelectric and pyroelectric applications

We have grown single crystals of lead-free (Na0.5Bi0.5)TiO3–(K0.5Bi0.5)TiO3 (abbreviated as BNKT) as promising materials for ferroelectric applications. The single crystals were grown by a high temperature self-flux solution method in which A-site compounds were used as complex flux. The crystal structure was analyzed by means of an X-ray diffraction technique showing a perovskite phase with tetragonal symmetry at room temperature. The surface morphology of the BNKT crystals was examined by scanning electron microscopy (SEM) and was found depicting a layered like hopper structure. The temperature and frequency dependence of the dielectric constant and loss for the as-grown single crystals was investigated, showing a decrease in Tmax from 316 °C at 50 kHz to 310 °C at 1 MHz. To study the degree of dielectric relaxation, modified power law fitting and Lorentz type quadratic fitting were performed. The relative composition of the studied sample and its phase transition behavior were confirmed by Raman spectroscopy. The piezoelectric coefficient d33 with optimized poling field was found to be 216 pC N−1. The ferroelectric response of the BNKT crystals with temperature at an applied field of 37 kV cm−1 was studied. The results suggest a promising approach for growing high quality alkali based single crystals with a relatively large size for piezoelectric and ferroelectric applications.

Sonia Bhandari

Papers

Synthesis and enhanced properties of cerium doped ZnO nanorods

Performance of crystal violet doped triglycine sulfate single crystals for optical and communication applications

Enhanced optical, dielectric and piezoelectric behavior in dye doped zinc tris-thiourea sulphate (ZTS) single crystals

Synthesis of 0.64Pb(Mg1/3Nb2/3)O3–0.36PbTiO3 ceramic near morphotropic phase boundary for high performance piezoelectric, ferroelectric and pyroelectric applications

Flux growth of lead free (Na0.5Bi0.5)TiO3–(K0.5Bi0.5)TiO3 ferroelectric single crystals and their characterization