Jungang Hou

Hierarchical assemblies of bismuth titanate complex architectures and their visible-light photocatalytic activities

The shape-controlled synthesis of hierarchically micro- and nanostructured materials has provided new possibilities to improve their physical and chemical properties. In this work, Bi12TiO20 complex architectures, such as nanospheres, nanowires, microflowers and microspheres were prepared through a facile solution-phase hydrothermal process, by controlling the reaction parameters, such as temperature, reagent concentration, and reaction time. Within the hydrothermal temperature range from 150 to 180 °C, the morphology transformed progressively from nanosphere agglomerates to microflowers, nanowires and then to microspheres with increasing time. A possible growth mechanism is proposed to explain the transformation of nanoparticles to microflowers via an Ostwald ripening mechanism followed by self-assembly and then break-up of the microflowers to nanowires and final consolidation into microspheres. Most importantly, these Bi12TiO20 samples dependent on their shape, size, and crystallinity, displayed high photocatalytic activities in comparison with bulk bismuth titanate powders, as demonstrated by the degradation of Rhodamine B under visible-light irradiation. The reasons for the difference in the photocatalytic properties of these Bi12TiO20 architectures are further investigated.

Solution-phase synthesis of single-crystalline Bi12TiO20 nanowires with photocatalytic properties

Single-crystalline sillenite-type bismuth titanate nanowires with photocatalytic properties have been synthesized via a simple solution-phase synthesis route.

Structural and relaxor characteristics of Ca0.18Sr0.226Ba0.594Nb2O6

Abstract Polycrystalline Ca0.18Sr0.226Ba0.594Nb2O6 (CSBN18) was synthesized via the solid-state reaction route. X-ray structural studies confirmed it belonged to the tetragonal tungsten bronze family. Rietveld refinement of the X-ray data has been carried out for CSBN18 where the atomic positions and site occupancy factors for A-sites have been determined. The dielectric properties of CSBN18 ceramic were studied as a function of temperature in the 100 Hz–1 MHz frequency range. The dielectric relaxation followed the Vogel–Fulcher relation wherein Ea = 37.4 meV; Tf = 131.5 °C and ω0 = 4.31 × 109 rad s−1. A high pyroelectric coefficient of ∼ 250 μC m−2.K was obtained around the transition temperature (∼150 °C). This is significantly higher than that reported for polycrystalline SrxBa1-xNb2O6 (SBN). However, the piezoelectric coefficient (d33) of the title composition was as low as 6 pC N−1.