Luqian Weng

Sol-gel processing of tellurium oxide and suboxide thin films with potential for optical data storage application

A novel sol-gel processing route has been developed for the production of tellurium oxide (TeO2) and tellurium suboxide (TeOx) thin films. The process has been used to deposit thin films on glass substrates by the dip coating process. These films have been shown to undergo thermally induced, reversible changes in optical properties on heating at appropriate temperatures. Formation of TeOx was found to occur at low temperatures by direct breakdown of the sol-gel derived material even in the absence of reducing agents whilst the principal optical effects corresponded to the formation of TeOx and α-TeO2 at temperatures of <200°C and <450°C respectively. The relatively low temperatures required to induce significant optical effects are comparable with conventionally prepared TeOx and offer the potential application of these materials in optical data storage systems.

Effect of acetylacetone on the preparation of PZT materials in sol-gel processing

Abstract Sol–gel processing is an advantageous route to produce PZT thin film materials with high quality. PZT powders and thin films with good properties were fabricated by sol–gel processing, using acetylacetone as modifier, in the study. The morphologies of PZT powders and thin films were observed by field emission microscopy, and the dielectric and properties of the PZT thin films were measured. Thermal analysis, XRD and FTIR were used to investigate the influence of ligands on the phase transformation in PZT materials, and it is found that the difficulty of decomposing acetylacetone ligands completely resulted in a higher pyrolysis temperature to form PZT with pure phase.

Multicomponent tellurite thin film materials with high refractive index

Abstract Sol–gel processing has been used to prepare optically transparent thin films in the system TeO 2 –TiO 2 . The structure and morphology of the thin films were investigated by X-ray diffraction (XRD) and field emission microscopy (FEM). The calculated refractive index, band gap and Urbach energy values for the thin films are consistent with the values obtained in other studies of conventionally melted tellurite and multicomponent tellurite glasses. The results show that the thin films by sol–gel processing offers an attractive route for the fabrication of such materials into devices.

Processing and characterisation of sol-gel glasses and powders in the system TeO2-TiO2

Sol-gel processing routes have been developed for the production of thin films and powders in the system TeO2-TiO2 from tellurium and titanium alkoxides. The structure and properties of the resultant materials have been characterised as a function of heat treatment temperature. Pure sol-gel derived TeO2 thin films are difficult to prepare with good optical transparency due to the presence of organic impurities and/or a highly dispersed metallic tellurium phase when heated at temperatures up to approximately 340°C, with crystallisation to α-TeO2 occurring when the heat treatment temperature is further increased. Additions of TiO2 were found to retard the crystallisation of the α-TeO2 but promote the formation of other TiO2 or TiTe3O8 phases. However, an optimum composition in the range 0.9TeO2 0.1TiO2 was identified, which allows optically transparent thin films to be prepared with high refractive index and offers the potential for practical device manufacture.

Sol-gel processing of tellurite powder

Tellurium ethoxide is highly sensitive to moisture in air and water. The hydrolysis and condensation of tellurium ethoxide exposed under different levers of water and moisture are investigated in this work and the hydrolysis products were characterised by infrared spectrometry and X-ray diffraction. The decomposition process of the product of tellurium ethoxide hydrolysed in air was analysed by differential scanning calorimetry and thermogravimetry. This work also studied the influence of sodium component on the phase transformation of the hydrolysis product in the decomposition process and on the morphology of the heat-treated hydrolysis products.

Low cost solid and quasi-solid electrolytes for photoelectro-chemical solar cells

SYNOPSIS This paper considers methods for cost-reduction of photoelectrochemical (Graetzel) solar cells.

Low-temperature processing of photoelectrochemical solar cells

Photoelectrochemical (or Gratzel) solar cells are normally manufactured by a process involving a sintering heat treatment of the TiO/sub 2/ photoanode, to provide mechanical and electrical contact between the nanoparticles. This precludes the use of many low cost substrates and alternative manufacturing approaches. This paper describes a new approach to engineer the nanostructure such that the heat treatment step can be eliminated whilst retaining acceptable device performance. The principles of and processes used to facilitate this are described and the device characteristics reported.