Huamei Shang

Dense and optical transparent CdWO4 films by sol-gel processing for scintillation applications

In this paper, we report the first successful fabrication of dense and opticallytransparent cadmium tungstate (CWO) films by sol-gel processing and the study oftheir optical and x-ray scintillation properties. A new sol-gel processing method wasdeveloped using tungstic acid and cadmium nitrate as precursors and hydrogenperoxide as solvent; homogeneous and stable CWO sols were aged at roomtemperature and used for the preparation of CWO films. A rapid sintering process wasinvestigated and found to be necessary to make dense and optically transparentnanocrystalline CWO films. CWO films were uniform, fully dense, and crack-free,with CWO as the only detectable crystalline phase, as determined by x-ray diffraction.The thickness, density, grain size, and crystallinity of CWO films are all found to bestrongly dependent on the sintering conditions and in turn impact the optical and x-rayscintillation properties. Sol-gel-derived dense CWO films demonstrated intensephotoluminescence and x-ray excited optical luminescence intensity. The relationshipsbetween sol-gel processing, nanostructures, and optical and x-ray scintillationproperties are discussed in detail.

Hydrothermal growth and photoluminescence property of textured CdWO4 scintillator films

Cadmium tungstate (CWO) films on glass substrate have been first prepared by hydrothermal method at temperatures ranging from 120 to 180 °C from cadmium nitrite and tungstic acid in hydrogen peroxide solution. Crack free and dense CWO films with textured structure and thickness up to 8 μm were formed at 150 and 180 °C as revealed by x-ray diffraction (XRD) and scanning electron microscopy (SEM) studied. Photoluminescence (PL) measurements revealed that highly textured CWO thick films possess better PL property. The growth mechanism and preferred orientation or textured structure as well as the relations between textured structure and PL property have been discussed.

Doping effects on microstructure and scintillation properties of cadmium tungstate films

This paper reports experimental study on the development of cadmium tungstate scintillator material in the form of nanocrystal films through controlled sol-gel processing and pre-designed doping. We chose cadmium tungstate as a base material for doping and nanostructure development due to its excellent inherent photoluminescence property. In addition, our studies revealed that doping with Li+, B3+ and Bi3+ resulted in appreciably reduced grain size and porosity, leading to enhanced optical transmittance. Further analyses indicated that photoluminescence output changed significantly with dopants. The relationships between doping, defects and luminescence were discussed.

Growth of Oxide Nanorod, Nanotube and Nanocable Arrays through Template-Based Sol Electrophoretic Deposition

This paper introduces a process for the growth of oxide nanorod, nanotube, and nanocable arrays that combines sol preparation and template-based electrophoretic deposition. Examples are shown that the sol electrophoretic deposition is an effective method for the formation of polycrystalline and single crystal oxide nanorod arrays, nanotube arrays and conformal coating of thin films of oxides on metal nanorods to produce metal-oxide core-shell nanocable arrays.

Processing and optical properties of sol-gel derived nanostructured CdWO 4 films

Dense and transparent cadmium tungstate (CWO) scintillation films have been first synthesized by sol-gel processing and their optical properties have been studied. Different precursors (tungsten oxychloride and tungstic acid), solvents (alcohol based and aqueous based) and thermal annealing processing conditions were investigated to achieve stable sols and resultant dense nanocrystalline CWO films. XRD showed CWO was the only detectable crystalline phase in the film derived by tungstic acid based sol and fast sintering at 500°C for 20 min, while the slow sintered films derived both from tungstic acid and tungsten oxychloride at 500°C for 1 hour with a heating ramp of 8°C/min resulted in porous films containing some extra tungsten oxide phases besides CWO. The fast sintered CWO film was uniform, fully dense, crack-free and of 0.5 μm in thickness. Optical transparency and photoluminescence of CWO films were characterized, and the results showed that high density and low porosity of CWO film by fast sintering led to higher transmittance and photoluminescence output. By controlling synthesis and sintering methods the nanocrystalline grains in CWO films can be of 15~52 nm in diameter. The relationships between sol-gel processing, precursor and solvent chemistry, nanostructures, densification and optical properties were discussed.