CaF2掺杂钨酸铅晶体的生长与闪烁性能

采用坩埚下降法生长了CaF2掺杂钨酸铅(PbWO4,PWO)晶体,研究了掺杂对PWO晶体的透射光谱、X射线激发发射谱和光产额等发光性能的影响.结果表明:与未掺杂PWO晶体相比,CaF2掺杂的PWO晶体在320～360nm的透过率提高了35%;X射线激发发射强度和光产额比未掺杂PWO晶体高出1倍左右.CaF2掺杂引入了新的发光中心(WO3-F),被认为是导致PWO晶体发光增强的原因.     

Ce∶LuAlO_3晶体的热稳定性研究

铈掺杂铝酸镥(Ce∶LuAlO_3)晶体是一种具有钙钛矿结构的新型无机闪烁体。用提拉法试图从n(Lu2O3)∶n(Al2O3)=1∶1的熔体中生长Ce∶LuAl O3晶体。实验表明在缓慢结晶条件下得到的不是Ce∶LuAlO_3晶体,而是镥铝石榴石[Lu3Al2(Al O4)3]。只有急速降温才能够获得Ce∶LuAl O3晶体。退火和差热分析表明Ce∶LuAl O3晶体只存在于高温条件下,当温度下降时,它会分解成Lu3Al2(Al O4)3,Lu4Al2O9和Lu2O3。造成LuAl O3晶体在低温下结构不稳定的原因是Lu离子的半径太小,它只适应于配位数是8的石榴石结构,只有在高温下才能适应配位数是12的钙钛矿结构。     

Ce:LuAlO3晶体的热稳定性研究

铈掺杂铝酸镥(Ce:LuAlO3)晶体是一种具有钙钛矿结构的新型无机闪烁体.用提拉法试图从n(Lu2O3):n(Al2O3)=1:1的熔体中生长Ce:LuAlO3晶体.实验表明:在缓慢结晶条件下得到的不是Ce:LuAlO3晶体,而是镥铝石榴石[Lu3Al2(AlO4)3].只有急速降温才能够获得Ce:LuAlO3晶体.退火和差热分析表明:Ce:LuAlO3晶体只存在于高温条件下,当温度下降时,它会分解成Lu3Al2(AlO4)3,Lu4Al 2O9和Lu2O3.造成LuAlO3晶体在低温下结构不稳定的原因是Lu离子的半径太小,它只适应于配位数是8的石榴石结构,只有在高温下才能适应配位数是12的钙钛矿结构.     

Bi和Nd共掺CsI晶体近红外宽带发光性能

采用坩埚下降法生长了Bi和Nd共掺的CsI晶体.X射线衍射分析表明,Bi和Nd共掺并不影响晶体结构,其空间群为Pm3m.通过测试晶体的实际掺杂浓度发现,共掺导致了Bi掺杂浓度的降低.对晶体进行退火处理,并测试了晶体的吸收光谱和发射光谱.结果表明:Bi和Nd共掺能够提高晶体中带电子色心V'Cs的浓度,经高温退火后能获得较多的低价态的Bi离子发光团簇,从而提高了晶体的近红外宽带发光性能.晶体的Raman 光谱显示,掺Bi的CsI晶体近红外宽带发光中心的2个特征Raman峰分别位于164和176 cm-1处.此外,还提出CsI晶体中发光中心Bi+和低价态团簇Bi2+的形成离不开高价态Bi离子的靠拢团聚作用.     

LiCaPO4:Eu3+荧光粉的制备及其发光性能的研究

用溶胶凝胶法制备了Eu3+单掺LiCaPO4荧光粉,探究了Eu3+的掺杂浓度、退火温度对荧光粉发光性能的影响.实验结果表明,当反应温度为900℃、退火时间为2 h、Eu3+掺杂浓度为5mol％时,荧光粉发光强度最强.XRD结果表明,样品为六方晶系Ca3(PO4)2与LiCaPO4的混相.利用CIE进行计算,结果表明,E...     

制备条件对铝掺杂氧化锌(AZO)薄膜结构和电学性质的影响

本文利用溶胶-凝胶法在玻璃基底上制备得到了AZO透明导电薄膜,就两种不同的热处理-退火方式对薄膜的结构与性质的影响做了比较,研究了掺杂浓度、退火温度对薄膜结构及性质的影响规律.结果表明,高温、分层退火、铝掺杂均有利于生成结晶度高、具有C轴优先取向的AZO薄膜;高温和分层退火有利于晶粒长大,相反铝掺杂却有碍晶粒长大;薄膜的电学性质随退火温度和铝掺杂量的变化呈现规律的变化.通过分析AZO薄膜内的晶体生长过程,本文认为主要是制备条件和AZO晶体的晶面习性导致了薄膜的结晶度、晶体生长取向性和晶粒尺寸等方面的差异.     

不同矿化剂浓度合成Zn1-xCoxO粉体研究

本实验采用水热法,以ZnSO_47H_2O为和Co(NO_3)_26H_2O为原料,以NaOH作为矿化剂(浓度为2 mol/L、3 mol/L、4 mol/L),在180℃保温24 h条件下,合成Zn_(1-x)Co_xO(x=0、0.05、0.1、0.15)稀磁半导体。通过XRD测试发现,矿化剂浓度对Co掺杂ZnO影响随着Co含量越高,峰值越低。扫描电镜显示:ZnO晶体呈针状,掺杂Co2+后,在长度方向上发生改变,当x=0.05时呈长方形块状,x=0.1时掺杂后的晶体呈块状,x=0.15时晶体以颗粒状的形貌出现,说明Co的掺杂在一定程度上影响了ZnO纳米晶体的生长。     

BaWO4:Eu3+/Tb3+荧光粉的制备及其发光性能的研究

采用共沉淀法制备了Eu3+、Tb3+单掺或双掺的BaWO4荧光粉,探究了Eu3+的掺杂浓度、退火温度及Eu3+和Tb3+掺杂摩尔比对荧光粉发光性能的影响.实验结果表明,当反应温度为500℃、退火时间为2h、Eu3+掺杂浓度为5 mol％时,荧光粉发光强度最强.XRD结果表明,样品为立方晶系的BaWO4相.在掺杂Eu3+...     

Yb:YCOB黄光激光自倍频晶体

采用提拉法生长了不同掺杂浓度(5％～30％,摩尔分数,下同)的Yb:YCa4O(BO3)3(Yb:YCOB)激光自倍频晶体,研究了系列晶体的结构与掺杂浓度之间的关系,加工了最大有效非线性系数方向的自倍频晶体并实现微片结构器件设计.利用强电—声子耦合作用,在掺杂浓度为30％、晶体长度为4 mm的Yb:YCOB晶体中获得了...     

杂质对磷酸二氢钾冷却结晶过程的影响

研究了MSMPR结晶器中Cl^-、Ca-、Ca⁽²⁺⁾、SO(2+)、SO^(2-)_4、NH(2-)_4、NH⁺_4对磷酸二氢钾结晶产品的产量、纯度、晶型等的影响。结果表明,杂质浓度的增大不利于晶体产量和纯度的增大;杂质的掺杂会影响晶体的晶型,出现晶体的变形、聚结。研究结果为磷酸二氢钾的结晶分离提纯提供了重要的参考依据。     

ZnWO_4~(4+)Ge~(4+)中Ge~(4+)对发光的影响

已经生长出不同掺杂浓度的ZnWO_4:Ge~(4+)单晶。ZnWO_4:Ge~(4+)单晶的吸收谱在323nm处有一个强的吸收带,有助于荧光效率的提高。ZnWO_4:Ge~(4+)单晶的激发谱由405nm、450nm和465nm三个带组成。ZnWO_4:Ge~(4+)单晶的能量分辨率可高达14.9％,因而可在辐射探测器和X射线接收器等方面得到应用。     

Microstructural development of a vitrified hindered phenol compound during thermal annealing

Structural changes in vitrified 3,9-bis{1,1-dimethyl-2[β-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionyloxy]ethyl}-2,4,8,10-tetraoxaspiro[5,5]-undecane (AO-80) during the annealing process were studied by DSC, WAXD and FT-IR. The initial AO-80 is highly crystalline, whereas AO-80 obtained by cooling from its melting state is an amorphous material. Annealing treatments below the melting point of AO-80 resulted in structural development. In addition, the modification of the crystal formed by annealing treatment depended on the annealing conditions. The IR spectra of various crystal modifications were different. Analysis of the microstructures of the crystals that formed indicated that the crystal formed by annealing at 100 °C is a smectic crystal, whereas the crystal formed by annealing at 80 °C is a nematic crystal. The AO-80 crystal formed within the chlorinated polyethylene (CPE) matrix during annealing at 100 °C is also a nematic crystal. Though the CPE matrix decreased regularity of AO-80 crystals, it raised the growth rate of AO-80 crystals.     

High-pressure and high-temperature annealing effects on CVD homoepitaxial diamond films

High-pressure and high-temperature (HPHT) annealing effects on the chemical vapor-deposited (CVD) homoepitaxial diamond films were investigated. By the HPHT annealing, the intensity of free-exciton (FE)-related emission was increased by  2 times and the luminescence bands from 270 to 320 nm, which originate from 5RL and 2BD bands, were almost completely eliminated in the cathodoluminescence (CL) spectrum. The CL intensity of band-A emission, which is related to crystal defects in diamond, was also decreased. The hole mobility at room temperature was increased from 826 to 1030 cm²/Vs by HPHT annealing. These results suggest that HPHT annealing decreases the crystalline defects and improves the optical and electronic properties of homoepitaxial diamond films.     

药品冷冻干燥过程的退火机理分析

运用热力学和动力学理论分析了药品冷冻干燥过程中的退火操作改变冻结药品结构的机理。通过对化学势随晶粒曲率半径变化、重结晶过程中冰晶半径随时间变化、非晶态基质的粘度随温度变化几个关系式的分析,得出退火温度必须要高于冻结药品的玻璃化转变温度;最佳退火持续时间与重结晶的速率紧密相关,且是退火温度的函数;退火后再冷却过程的冷却速率不影响升华干燥速率等结论。     

导模法生长蓝宝石晶体的退火工艺

采用导模法生长了片状蓝宝石单晶。由于石墨发热体的高温挥发,使晶体尾部产生黑色絮状包裹体,晶体内部生成色心。为了消除片状蓝宝石晶体内的包裹体和色心,在不同气氛下对生长的晶体样品进行了退火处理。退火实验表明,含有包裹体的尾部样品在1500℃空气中退火20h并以50℃／h的速率降温,可消除晶体内的碳包裹体,晶体变为无色、透明。在氢气中1600℃退火37h后,F色心引起的205mm的吸收峰和Fe^3＋所引起的200～230的吸收峰均被消除。表明高温氢气中退火是消除导模法生长蓝宝石晶体内部F色心和Fe^3＋吸收的最佳退火方法。     

钛宝石晶体中的位错以及退火对位错的影响

用化学腐蚀剂腐蚀出样品的 (0 0 0 1)表面上的位错蚀坑 ,在原生态和退火样品的对应径向线上测量了位错腐蚀坑的密度分布 .由位错腐蚀坑的形成理论确定出原生态晶体中很可能有 3种位错类型 ,即Burgers矢量b =13〈112 0〉 ,13〈110 1〉和〈10 10〉的位错线 ,然而长时间在还原性高温气氛中的退火难以降低晶体中的总的位错密度 .在晶体的放肩至等径生长阶段 ,沿着晶体的生长方向 ,晶体棒中心的位错密度由高变低 ,这显示出 :在晶体的放肩至等径生长的转变过程中 ,生长界面发生了翻转 ,由凹形界面转变为凸形界面 ,位错线随之从晶体棒的中心向边缘发散 .     

高剂量中子辐照6H-SiC晶体的退火特性

在温度为60～80℃的条件下用剂量为1.72×1019n/crm2的中子对6H-SiC晶体进行了辐照,利用X射线衍射等方法观测了中子辐照引起的缺陷及其恢复.重点追踪6H-SiC的(006)、(0012)晶面的衍射峰并进行实验观测.中子辐照对晶体造成了严重的损伤,使其内部产生了大量的缺陷,在某些被测晶面甚至出现非晶化.通过等时退火,缺陷逐渐消失,晶格开始恢复,其恢复特性由退火温度决定.通过X射线衍射峰的峰高和峰型发现,在温度低于600℃时,辐照损伤几乎不变,超过600℃后,温度越高,晶格恢复现象越明显.原来经辐照呈非晶化的晶面逐渐恢复有序,(006)面衍射峰的半高宽随退火温度的升高呈线性恢复.利用此种线性规律可以制作无线传感器,从而实现对某些复杂环境的温场测试.     

Electron emission from diamond thin films deposited by microwave plasma-chemical vapor deposition method

Diamond films with different crystal structures, morphologies and surface characteristics were synthesized under various deposition parameters and annealing conditions by the microwave plasma chemical vapor deposition (MWPCVD) method using gas mixtures of CH₄, CO and H₂. The effects of CH₄ concentrations, grain sizes, grain orientations, film thicknesses and annealing technologies in various ambient gases on planar electron emission of diamond films were studied. The results show that small-grained and (011)-oriented diamond films deposited under the condition of high CH₄ concentration present the properties of high emission current and low threshold voltage; the emission current increases with decreasing the film thickness. There are largest current density and lowest threshold voltage at the film thickness of 1.5 μm. The annealing in H₂ after deposition appears to be more beneficial in lowering the threshold voltage, increasing emission current and improving stability for electron emission of films than annealing in N₂ or Ar. These results indicate that diamond thin films with high emission current, low threshold voltage and high stability can be obtained by selecting suitable deposition parameters of diamond films.     

A new synergistic effect in one step sputtered ZnO/Zn2SnO4 heterojunction films for H2 sensing related to crystal structure and film compactness

In this paper, ZnO/Zn₂SnO₄ heterojunction films were one step fabricated by magnetron sputtering and the dependence of crystal structures, film compactness and H₂ sensing properties on annealing process were investigated and discussed. The results showed that three typical surface morphologies can be controlled by adjusting annealing temperatures and periods. The films annealed at the temperature of 550 °C for 6 h showed the best H₂ sensing properties. It exhibited a response (R_a/R_g) of 28.3–100 ppm H₂ at the temperature of 230 °C and the detection limit is 30.2 ppb. Meanwhile, it also showed a good selectivity and long-term stability to H₂. The H₂ sensing mechanism is attributed to the synergistic effect between ZnO (0001) signal crystal facets and ZnO/Zn₂SnO₄ heterojunction structures which enhanced the gas reactivity and resistance modulation range. On the contrary, insufficient annealing restricts the film crystallinity and the growth of hexagonal ZnO while undue annealing destroys the compactness of the films, leading to poor H₂ sensing properties.     

Influence of thermal processing on the perfection of crystals in polyamide 66 and polyamide 66/clay nanocomposites

A study of the changes in crystal perfection of polyamide 66 (PA66) and polyamide 66/clay nanocomposites (PA66CN) due to different thermal processing was carried out. We designed three series of thermal processing including melt-quench (MQ), post-annealing MQ sample (MQA), and melt–slow cooling–annealing (MSA). The annealing temperature was set as 180 or 210 °C, which is within Brill temperature range of PA66. Fourier transform infrared (FT-IR) spectroscopy and wide angle X-ray diffraction (WAXD) were employed to characterize the perfection in short-range order and long-range order structures, respectively. The results showed that the crystal perfection of PA66 and PA66CN with different thermal processing is quite different, and the changing fashions with thermal processing for different ordered structures are not similar. In this work, MSA is optimal thermal processing for high crystallinity and crystal perfection. Exfoliated nanoclay layers exert considerable impact on the perfection of long-range ordered structures, but little on that of short-range ordered ones.