Preparation of Rod-like Aluminum Doped Zinc Oxide Powders by Sol-gel Technique Using Metal Chlorides and Acetylacetone Precursors

Al-doped ZnO(AZO) powders were prepared by using metal chloride precursors and the sol-gel technique. IR peaks observed at 1590 cm-1 and 1620 cm-1indicated the formation of metal chelate as a consequence of the addition of acetylacetone to the metal chloride solution. TG-DSC analysis of the AZO gels confirmed the formation of metal chelate as evidenced by the development of several weight loss peaks accompanied by the introduction of new endothermic peaks. The resulting AZO gels were annealed at 500, 600, and 800 ℃ to study the effect of annealing temperature. XRD and SEM results showed that crystallization of AZO gels takes place around 600 ℃. Hexagonal wurtzite structure was identified as the main phase for all the samples. In addition, small shift of the XRD(002) peak coupled with XPS results from the AZO powders confirmed the successful doping of the ZnO powders. Micron sized rod-like AZO powders were uniform in dimension and morphology and remained stable even at 800 ℃.

Application of Stereology on Neodymium-Doped Yttrium Aluminum Garnet (Nd∶YAG) Transparent Ceramics

Nd ： YAG precursor powders were synthesized by homogeneous precipitation, and Nd ： YAG transparent ceramics were prepared by vacuum sintering at 1700 ℃ for 5 h. The ceramic materials were characterized by light transmittance and field emission gun-environment scanning microscope. Using statistics and stereology theory, study was carried out on the quantitative relationships between light transmittance and stereological parameters in three-dimensional Euclidean space. It is found that the transmittance of Nd：YAG with 1 mm in thickness is about 45% and 58% in visible and near-infrared wavelength, respectively. The transmittance linearly increases with increasing equivalent sphere diameter and reaches the theoretical value of single crystal when the equivalent sphere diameter is 20μm. The transmittance decreases with the increasing of mean specific area per unit volume of grain and discrete grains, and the transmittance decreases with increasing mean free distance of grains in Nd：YAG ceramics.

Dose-Dependence of Trap Parameters of OSL Decay from Al_(2)O_(3):C

Optically Stimulated Luminescence (OSL) trap parameters can only be reliably determined through the detailed analy- sis of OSL decay curves. In this study the kinetic parameters of a blue-light stimulated luminescence (BLS) decay curve from Al2O3:C sample irradiated at 0.1, 0.15, 0.2, 0.4 and 0.6 Gy beta doses were obtained using the same basic methods with some modifications applied and also by using our suggestion: Active-OSL Approximation (AOSL). The results were compared with those of other studies on the trap parameters of Al2O3:C material.

Controlled Synthesis and Application of α-Al_2O_3 for Lu_3Al_5O_(12): Ce^(3+) Green Spherical Phosphors

Al2O3 powders with different morphologies,namely fibrous,sheet-like,and spherical,were prepared by the hydrothermal-thermolysis method.Subsequently,polycrystalline,transparent cerium doped lutetium aluminum garnet（Lu3Al5O（12）：Ce^3＋）green phosphors were synthesized by high temperature solidstate method using commercial lutetium（III）oxide,cerium（III）oxide,and as-prepared Al2O3 powders with different morphologies.The phases,morphologies,and photoluminescent properties of the prepared phosphors were investigated by X-ray diffraction（XRD）,scanning electron microscopy（SEM）,and photoluminescence spectroscopy（PL）.Moreover,the influences of the morphologies ofα-Al2O3 on the types of crystal structure,morphologies,and photoluminescent properties of LuAG：Ce^3＋green phosphors were investigated.The results indicated that the morphologies and particle sizes of theα-Al2O3 powders could be controlled by the additives and parameters.Notably,the sphericalα-Al2O3 powders with good dispersibility were found to be the excellent base materials of LuAG：Ce^3＋green phosphors for white light emitting diodes.

Aluminum doping for optimization of ultrathin and high-k dielectric layer based on SrTiO3

An ultrathin SrTiO3 dielectric layer is optimized through Al doping to solve the problems existing in development of ultra-high-k oxide MOS capacitors.Through post-deposition annealing,Al doping induces changes in the electronic structure of SrTiO3,thereby effectively reducing leakage current to <10^-8 A/cm^2 at 0.5 MV/cm but maintains good capacitance values(ε> 80) of ultrathin SrTMO3 MOS capacitors.Strontium titanate(SrTiO3) is a high-k material but its bandgap is smaller than that of other oxide dielectrics(e.g.,SiO2,Al2 O3).Consequently,an ultrathin SrTiO3 film may have a high tunneling leakage current,which is not suitable for capacitor-based applications.To improve the performance of metal-oxide-semiconductor(MOS) capacitors using SrTiO3,an approach based on homogenous and uniform aluminum doping to SrTiO3 through co-sputtering is introduced.The bandgap of a pristine SrTiO3 film showed an increase of 0.5 eV after Al doping.Furthermore,Al doping decreased the leakage current of SrTiO3/Si-based MOS capacitors by more than five orders of magnitude(at the level of nanoampere per square centimeter).Importantly,a dielectric constant of 81.3 and equivalent oxide thickness less than 5 A were achieved in an 8-nm-thick Al-doped SrTiO3 film owing to changes in its crystal structure and conduction band edge electronic structure.Thus,the obtained data show the effectiveness of the proposed approach for solving the problems existing in the development of ultra-high-k oxide MOS capacitors.

Study of Graphene Doped Zinc Oxide Nanocomposite as Transparent Conducting Oxide Electrodes for Solar Cell Applications

The graphite oxide(GO) was prepared based on the modified Hummers method, then reacted with zinc acetate aqueous, sodium hydroxide aqueous and hydrazine hydrate, and was doped into ZnO eventually to form graphene doped ZnO, an alternative transparent conducting oxide(TCO) for solar cell applications. The samples were characterized by Raman spectrometer, X-ray diffractometer, Fourier transform infrared spectroscopy and scanning electron microscope, and compared with widely used aluminum doped ZnO(AZO) in resistivity and transmissivity. The results show that the transmissivity of graphene doped ZnO reaches the same level as that of AZO in visible light band. In ultraviolet light wave band, the transmissivity of graphene doped ZnO reaches as high as 50%, exceeding that of AZO which is only 20%. The resistivity of optimized graphene doped ZnO is1.03 × 10-5Ω· m, approaching AZO resistivity which is about 10-4—10-6Ω· m. As a result, graphene doped ZnO may have potential applications in the area of TCO due to its low cost and high performance.