The influence of temperature fields on the crystallisation kinetics of high-density polyethylene during injection moulding was disclosed in this work. The dimensionless X = 0.4 along the part thickness was a critical location, within which the heat transfer of polymer was primarily affected by thermal conduction. When X > 0.4, the decay in temperature tended to become stable with limited variation in t(1/2)(-1) value (an indicator of average crystallisation rate). The experimental results indicated that the crystallisation rate was proportional to the cooling speed, regardless of the cooling conditions utilised. The sequence of relative crystallinity was in consistence with that of secondary temperature difference. The present study will be of practical significance to further investigation on the 'processing-structure-property' relationship for polymeric materials.

Gamma-rays radiation effects on Ce:YAG crystals grown by Czochralski (Cz) and temperature gradient techniques (TGT) have been studied by means of optical absorption and luminescence spectra. Valence of Ce3+ ion changes during the gamma-ray irradiation process and this result indicates Ce4+ ion may exist in both Cz-Ce:YAG and TGT-Ce:YAG crystals. Thermally stimulated luminescence measurements reveal intense thermoluminescence peaks in gamma-irradiated Ce:YAG crystals and trap parameters were calculated by general-order kinetics expression. (C) 2006 Elsevier B.V. All rights reserved.

YAlO3 (YAP) crystals with different Yb3+ concentration have been grown by Czochralski method and cooperative fluorescence of Yb3+ ions in YAP crystal was studied under 940-nm infrared (IR) LD excitation at room temperature. The Yb concentration dependence of absorption intensity of IR and charge transfer bands exhibit different features. The green emission band in the region of 480–520nm was assigned to the cooperative deexcitation of two Yb3+ ions. The remaining upconverted emission bands containing various sharp peaks associated with impurity ions were observed and discussed. Charge transfer luminescence of heavily doped 20at% Yb:YAP is strongly temperature dependent and no concentration quenching of the charge transfer luminescence was found through the investigation of different Yb levels samples.

ZnO thin films have been fabricated by pulsed laser deposition(PLD) technique on(MgO(100)) substrates.Substrate temperatures were varied in the range of 400-700℃.The structural and optical properties were characterized with X-ray diffraction(XRD) and photoluminescence(PL),respectively.XRD results indicated that the ZnO films grown at 400℃ and 550℃ were all highly c-axis oriented.But the micro-structure of the ZnO film changed to the one with multi-orientation when the substrate temperature(increased) to 700℃. It has been observed that the exciton emission dominates in the photoluminescence spectra,and concluded that the intensity of the UV luminescence strongly depends on the crystalline quality of the ZnO films.

Gamma-ray irradiation induced color centers and charge state recharge of impurity and doped ion in 10 at.% Yb:YAP have been studied. The change in the additional absorption (AA) spectra is mainly related to the charge exchange of the impurity Fe2+, Fe3+ and Yb3+ ions. Two impurity color center bands at 255 and 313 nm were attributed to Fe3+ and Fe2+ ions, respectively. The broad AA band centered at 385 nm may be associated with the cation vacancies and F-type center. The transition Yb3+ → Yb2+ takes place in the process of γ-irradiation. Oxygen annealing and γ-ray irradiation lead to an opposite effect on the absorption properties of the Yb:YAP crystal. In the air annealing process, the transition Fe2+ → Fe3+ and Yb2+ → Yb3+ take place and the color centers responsible for the 385 nm band was destroyed.

ZnO thin films were grown by magnetron sputtering technique on Si(111) substrates,some of those films were annealed at different temperatures from 300℃ to 600℃ in vacuum and the others were annealed at different temperatures from 300℃ to 900℃ in the air.The influences of annealing temperature and condition on the quality,grain size and photoluminescence of ZnO films are discussed in this article.X-ray diffraction patterns indicated that the films were C-axis oriented.When the annealing temperature was lower than 900℃,the grain size increased with the increase of annealing temperature.The emission spectra excitated by 325nm were measured at room temperature,and a 380nm emission was observed when the annealing temperature was lower than 400℃.Two ultraviolet luminescence peaks were observed when the annealing temperature was from 400℃ to 600℃.When the annealing temperature was the same as or high than 600℃,a 380nm emission and a 530nm emission were observed.These results indicate that ZnO thin films by magnetron sputtering on the silicon substrates are high quality films.At the same time,the crystal quality and optical properties of ZnO thin films can be improved through changing annealing temperature and condition.

Gamma-ray irradiation-induced color centers in Al2O3 crystals grown by temperature gradient techniques (TGT) under a strongly reducing atmosphere were studied. The transition F+ -> F takes place during the irradiation process. Glow discharge mass spectroscopy (GDMS) and annealing treatments show that Fe3+ impurity ions are present in the crystals. A composite (F+-Fe3+) defect was presented to explain the origin of the 255 nm band absorption in the TGT-Al2O3 crystals. (C) 2006 Elsevier B.V. All rights reserved.

ZnO thin films were fabricated by pulsed laser deposition(PLD)technique on Al_2O_3 substrates.Substrate temperatures were varied in the range of 300-700℃.The structural and optical properties were characterized with X-ray diffraction(XRD)and photoluminescence(PL),respectively.XRD results indicated that the ZnO films were all highly c-axis oriented.The rocking curve displayed that the crystal quality of ZnO films obviously improved when the substrate temperature was changed from 300℃ to 400℃.It has been observed that the exciton emission dominates in the photoluminescence spectra,and concluded that the intensity of the UV luminescence strongly depends on the substrate temperatures.The peak location was blue-shift 6nm when the substrate temperature was changed from 300℃ to 400℃ at the same time.

Photoluminescence spectrum of Ce:YAG single crystal was studied employing vacuum ultraviolet (VUV) synchrotron radiation. Intrinsic absorption edge at about 52,000cm−1 was observed in the absorption spectrum. From the VUV excitation spectrum, the energy of the highest d-component of 53,191cm−1 (188nm) for the Ce3+ ions in YAG was obtained at 300K. The disappearance of the third 5d level at 37,735cm−1 (265nm) in absorption and excitation spectra in our samples may be due to the impurity Fe3+ ions absorption.

Color centers and impurity defects of Ce:YAG crystals grown in reduction atmosphere by temperature gradient techniques have been investigated by means of gamma irradiation and thermal treatments. Four absorption bands associated with color centers or impurity defects at 235, 255, 294 and 370nm were observed in as-grown crystals. Changes in optical intensity of the 235 and 370nm bands after gamma irradiation indicate that they are associated with F+-type color center. Charge state change processes of Fe3+ impurity and Ce3+ ions take place in the irradiation process. The variations of Ce3+ ions concentration clearly indicate that Ce4+ ions exist in Ce:YAG crystals and gamma irradiations could increase the concentration of Ce3+ ions. Annealing treatments and the changes in optical density suggest that a heterovalent impurity ion associated with the 294nm band seems to be present in the crystals.

Optical properties for ZnO thin films grown on (100) γ-LiAlO2 (LAO) substrate by pulsed laser deposition method were investigated. The c-axis oriented ZnO films were grown on (100) γ-LiAlO2 substrates at the substrate temperature of 550°C. The transmittance of the films was over 85%. Peaks attributed to excitons were shown in absorption spectra, which indicated that thin films had high crystallinity. Photoluminescence spectra with the maximum peak at 540 nm were observed at room temperature, which seemed to be ascribed to oxygen vacancy in the ZnO films caused by diffusion of Li from the substrates into the films during the deposition.

The emission spectra of the ZnO films deposited on MgO(100),α-Al_2O_3(0001) and MgAl_2O_4(111) substrates by pulsed laser deposition(PLD) were studied. A 430nm blue emission peak was observed. The intensity changes of the blue peak of the annealed ZnO films were investigated. It is concluded that the blue emission originates from the interstitial Zn and the transition of electrons from the shallow donor level of the oxygen vacancies to the valence band. The excitation wavelength and substrates also have effects on the optical properties of the ZnO films.The ZnO film deposited on MgO substrate and excited with 350nm light shows the strongest blue emission.

ZnO thin films were deposited on the substrates of (100) gamma-LiAlO2 at 400, 550 and 700 degrees C using pulsed laser deposition (PLD) with the fixed oxygen pressure of 20 Pa, respectively. When the substrate temperature is 400 degrees C, the grain size of the film is less than 1 mu m observed by Leitz microscope and measured by X-ray diffraction (XRD). As the substrate temperature increases to 550 degrees C, highly-preferred c-orientation and high-quality ZnO film can be attained. While the substrate temperature rises to 700 degrees C, more defects appears on the surface of film and the ZnO films become polycrystalline again possibly because more Li of the substrate diffused into the ZnO film at high substrate temperature. The photoluminescence (PL) spectra of ZnO films at room temperature show the blue emission peaks centered at 430 nm. We suggest that the blue emission corresponds to the electron transition from the level of interstitial Zn to the valence band. Meanwhile, the films grown on gamma-LiAlO2 (LAO) exhibit green emission centered at 540 nm, which seemed to be ascribed to excess zinc and/or oxygen vacancy in the ZnO films caused by diffusion of Li. from the substrates into the films during the deposition.

采用溶胶-凝胶法制备了不同组分(x=0.1～0.3)的MgxZn1-xO前驱体,并对它进行不同温度的热处理(550℃～1000℃).X射线衍射(XRD)结果表明,Mg0.1Zn0.9O具有和ZnO一样的衍射谱,为六方纤锌矿结构,而且随着热处理温度的升高,ZnO衍射峰的强度逐渐增强,半高宽不断减小;Mg元素掺杂浓度增大后,出现了MgO的峰位.扫描电子显微镜(SEM)显示Mg0.1Zn0.9O晶粒粒径分布较均匀;热处理温度升高,晶粒的尺寸不断变大.用室温荧光光谱(PL)分析了经过550～1000℃热处理获得的Mg0.1Zn0.9O粉末,结果发现除了550℃下处理的样品,其它都有紫外发射峰(350nm左右),而且随着热处理温度的升高紫外峰有明显的蓝移现象.

High quality sapphire crystal oriented along [ 0001 ] was grown by the temperature gradient technique. The etch pits in (0001) plane were observed by scanning electron microscope (SEM), and the inclusions were analyzed by energy dispersive spectroscopy (EDS). The defects observed in as-grown crystal mainly originate from dislocations and inclusions. The shape of etch pits located in (0001) plane of Al2O3 crystal exhibits as a hexagon with sidestep-like structure. The type of dislocations of (0001) slices was studied by SEM images. The components of inclusions in sapphire crystal grown by TGT method are identified as carbon.

Co-doped ZnO powder and thin films on Si(1 0 0) substrate were prepared by solid-phase reaction and reactive e-beam evaporation. All samples were characterized by X-ray diffraction. The structure of powder sample was determined using Rietveld full-profile analysis method. The study of the influence of substrate temperature on the structure of thin films samples showed that the quality of thin films depended largely on the substrate temperature. The film prepared at 400 °C had the highest quality with c-axis (0 0 2) preferred orientation.

Co-doped ZnO powder and thin films on Si(1 0 0) substrate were prepared by solid-phase reaction and reactive e-beam evaporation. All samples were characterized by X-ray diffraction. The structure of powder sample was determined using Rietveld full-profile analysis method. The study of the influence of substrate temperature on the structure of thin films samples showed that the quality of thin films depended largely on the substrate temperature. The film prepared at 400 deg. C had the highest quality with c-axis (0 0 2) preferred orientation.

用电子束蒸镀方法在（100）单晶Si衬底上,生长Zn0.85Co0.15O薄膜,并研究了衬底温度对薄膜质量的影响,结果表明当衬底温度为400℃时,外延膜取向性最好,且其（002）衍射峰半高宽最窄（为0.4834°）。