钛宝石中子辐照色心的研究

研究了中子辐照下钛宝石单晶体缺陷的形成及光学性能的变化。对温度梯度法(TGT)生长的钛宝石晶体进行中子辐照。中子能量为1．5MeV，剂量为4．32×10^18 neutrons／cm^2。辐照后194nm吸收峰强度增加,268nm吸收峰强度则降低。荧光谱检测中发现辐照使得420nm荧光峰强度明显降低，荧光峰位置也蓝移至414nm处。分析表明辐照使得钛宝石晶体内形成F^+缺陷，同时Ti^4+离子则转化成Ti^3+离子。辐照后的钛宝石在247C处有热释光TL出现，通过初始上升法计算出其陷阱深度为0．63eV。

蓝宝石中子辐照色心的研究

研究了中子辐照对蓝宝石(α-Al2O3)单晶体缺陷形成及光学性能的影响，对采用提拉法与温度梯度法生长的蓝宝石晶体进行中子辐照，通过对比辐照前后的吸收及荧光光谱变化，发现辐照使得蓝宝石晶体内形成F、F^+和F2^+色心缺陷，但不同方法生长的晶体样品中色心浓度差异明显。其中提拉法样品的F心浓度要高于温度梯度法样品，而温度梯度法样品中F^+色心浓度要高于提拉法样品。分析表明，这与两种方法生长的晶体中杂质含量差异有关。通过研究辐照后晶体的热致发光谱发现提拉法与温度梯度法生长的蓝宝石晶体分别在145℃与150℃有明

Defects in U3+: CaF2 single crystals grown under different conditions by the temperature gradient technique

Defects in as-grown U3+ : CaF2 crystals grown with or without PbF2 as an oxygen scavenger were studied using Raman spectra, thermoluminescence glow curves, and additional absorption (AA) spectra induced by heating and gamma-irradiation. The effects of heating and irradiation on as-grown U3+: CaF2 crystals are similar, accompanied by the elimination of H-type centers and production of F-type centers. U3+ is demonstrated to act as an electron donor in the CaF2 lattice, which is oxidized to the tetravalent form by thermal activation or gamma-irradiation. In the absence of PbF(2)as an oxygen scavenger, the as-grown U3+:CaF2 crystals contain many more lattice defects in terms of both quantity and type, due to the presence of O2- impurities. Some of these defects can recombine with each other in the process of heating and gamma-irradiation. (c) 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Gamma-irradiation effects on Ce-doped YAG crystals grown by Cz and TGT method

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.

Growth of highly sensitive thermoluminescent crystal alpha-Al2O3 : C by the temperature gradient technique

In this work, an alpha-Al2O3:C crystal with highly sensitive thermoluminescence was directly grown by the temperature gradient technique (TGT) using Al2O3 and graphite powders as raw materials. The optical and luminescent properties and the dosimetric characteristics of the crystal were investigated. An as-grown alpha-Al2O3:C crystal shows a single glow peak at 462 K and a blue emission peak at 415 nm. The thermoluminescence (TL) response of the crystal shows a linear-sublinear-saturation characteristic. In the dose range from 5 x 10(-6) to 10Gy, the alpha-Al2O3:C crystal shows excellent linearity, and saturation was observed at about 30Gy. The sensitivity of the crystal decreases as the heating rate increases. (c) 2008 Elsevier B.V. All rights reserved.

α-Al_2O_3:C晶体的热释光和光释光特性

以高纯α-Al2O3和石墨为原料,采用温梯法生长了α-Al2O3:C晶体,使用RisΦTL/OSL-DA-15型热释光和光释光仪研究了其热释光和光释光特性.α-Al2O3:C晶体在462K附近有单一热释光峰,发射波长位于410nm.随着辐照剂量的增加,热释光强度逐渐增强,462K的热释光特征峰位置保持不变.α-Al2O3:C晶体的光释光衰减曲线由快衰减和慢衰减两个部分组成,随着辐照剂量的增加,快衰减部分衰减速率变化不大,而慢衰减部分衰减速率加快.在5×10-6—10Gy剂量范围内,α-Al2O3:C晶体的热释光剂量响应呈现良好的线性关系,30Gy时达到饱和;光释光剂量响应在5×10-6—60Gy剂量范围内呈现良好的线性关系,100Gy时达到饱和.与热释光相比,光释光剂量响应具有更高的灵敏度和更宽的线性剂量响应范围.

Growth of alpha-Al2O3:C crystal with highly sensitive optically stimulated luminescence

In this work. an alpha-Al2O3:C crystal was directly grown by the temperature gradient technique (TGT) using Al2O3 and graphite powders as the raw materials. The optical, optically stimulated luminescence (OSL) properties and dosimetric characteristics of as-grown crystal were investigated. As-grown alpha-Al2O3:C crystal shows strong absorption band at 205, 230 and 256 nm. Three-dimensional thermoluminescence (TL) emission spectrum of the crystal shows a single emission peak at similar to 415 nm. The OSL decay curve can be fitted to two exponentials, the faster component and the slower component. The OSL response of the crystal shows a linear-sublinear-saturation characteristic. As-grown alpha-Al2O3:C crystal shows excellent linearity in the dose range from 5 x 10(-6) to 50 Gy. For doses higher than the saturation dose (100 Gy). the OSL sensitivity decreases as the dose increases. Crown Copyright (C) 2008 Published by Elsevier B.V. All rights reserved.

Deep levels in high resistivity GaN detected by thermally stimulated luminescence and first-principles calculations

Thermally stimulated luminescence spectroscopy has been applied to study the deep centres in unintentionally doped high resistivity GaN epilayers grown by the metal organic chemical vapour deposition method on c-sapphire substrates. Two trap states with activation energies of 0.12 and 0.62 eV are evaluated from two luminescence peaks at 141.9 and 294.7 K in the luminescence curve. Our spectroscopy measurement, in combination with more accurate first-principles studies, provided insights into the microscopic origin of these levels. Our investigations suggest that the lower level at 0.12 eV might originate from C-N, which behaves as a hole trap state; the deeper level at 0.62 eV can be correlated with V-Ga that corresponds to the yellow luminescence band observed in low-temperature photoluminescence spectra.

稀土固体剂量计材料的合成、发光及剂量光学性质

采用高温固相扩散反应合成了稀土元素激活的碱土硼酸盐MB4O7:RE（M=Sr， Ba；RE＝D又Tb，Tm， Ho）；过渡金属硼酸盐Zn4B6O13：RE（RE＝Dy,Tb，Tm，Ho）； Zn（BO2）2:RE（RE＝Dy,Tb，Tm，Ho）；碱土磷酸盐M3（PO4）2:RE（M=Sr，Ba；RE＝Du, Tb）。通过）。RD和琅光谱对其结构进行了表征。测定了上述化合物的红外、荧光、余辉、漫反射和热释光谱及剂量学性质。研究了高能60Co伽玛射线和p-射线辐照下，稀土离子激活的碱土硼酸盐 MB407：Dy（M=Sr，Ba）；过渡金属硼酸盐Zn4B6O13:Dy；Zn（BO2）2：Dy，Zn毋o承：Tb； 碱土磷酸盐Sr3（PO4）2:Dy的三维热释光谱及MB4O7:Dy（M=Sr，B）的电子顺磁共 振谱（EPR）的性质。发现稀土离子激活剂的浓度在一定的范围内增加时，能够改变陷阱的分布，不同深度陷阱的相对分布发生变化，使峰温向高温方向移动，这可提高剂量器的 热稳定性。发现稀土离子对材料的热释发光亦存在浓度碎灭作用。通过热释发光曲线；结合定量公式，计算了一些硼酸盐化合物的动力学参数。首次应用荧光、三维热释光谱等手段确证了高能60Co伽玛射线和p-射线辐 照没有导致稀土离子D3+和Tb3+的价态变化，即未改变为二价或四价化合物。研究了这类电子俘获材料的存储机理和辐照前后，基质和稀土离子的物理、化学 变化。通过电子顺磁共振谱卿）分析了缺陷的类型，即在高能60Co伽玛射线和p 一射线辐照下，存在空穴和电子两类陷阱中心。热释发光曲线与电子顺磁共振谱 的快衰退部分对应着浅陷阱能级，而慢衰退部分对应着深陷阱能级，陷阱能级是 连续分布的。在个人防护和临床治疗剂量范围内，筛选出7个60Co伽玛射线和中能x一射 线辐照下具有应用前景的高效热释发光材料，为深入研究打下基础。研究了高能p-射线辐照下，两．种潜在的具有应用前景的用于辐射加工剂量范围的p-射线固体剂量计材料。

Absorption and luminescence of the surface states in ZnS nanoparticles

A broad absorption band around 500 nm is observed in ZnS nanoparticles. The absorption becomes more intensive and shifts to the blue as the particle size is decreased. The absorption energy is lower than the band gap of the particles and is considered to be caused by the surface states. This assignment is supported by the results of the fluorescence and of the thermoluminescence of the surface states. Both the absorption and the fluorescence reveal that the surface states are size dependent. The glow peak of the semiconductor particles is not varied as much upon decreasing size, indicating the trap depth of the surface states is not sensitive to the particle size. Considering these results, a new model on the size dependence of the surface states is proposed, which may explain our observations reasonably. (C) 1997 American Institute of Physics.

Comparison doses of secondary neutron with the heavy ions in a 75-mev/n heavy ion beam

国科图

Luminescent properties of a new blue long-lasting phosphor Ca2P2O7:Eu2+, Y3+

A new pyrophosphate long-lasting phosphor with composition of Ca1.96P2O7:0.02Eu(2+), 0.02Y(3+) is synthesized via the high-temperature solid-state reaction method. Its properties are systematically investigated utilizing XRD, photoluminescence, phosphorescence and thermoluminescence (TL) spectra. The phosphor emits blue light that is related to the characteristic emission of Eu2+ due to 5d-4f transitions. For the optimized sample, bright blue long-lasting phosphorescence (LLP) could be observed by naked eyes even 6 h after the excitation source is removed. The TL spectra show that the doping of Y3+ ions greatly enhanced intensity of 335 K peak and created new TL peak at about 373 K that is also responsible for the blue LLP. Based on our study, Y3+ ions are suggested to act as electron traps to improve the performance of the blue phosphorescence of Eu2+ such as intensity and persistent time.

Blue long lasting phosphorescence of Tm3+ in zinc pyrophosphate phosphor

Phosphate long lasting phosphorescence (LLP) phosphors with composition of (Zn1-xTmx)(2)P2O7 were prepared by the high-temperature solid-state method. Their properties were systematically investigated utilizing XRD, photoluminescence, phosphorescence and thermoluminescence (TL) spectra. These phosphors emit blue light that is related to the characteristic emission due to the D-1(2)-H-3(6), D-1(2)-H-3(4) and (1)G(4)-H-3(6) transitions of Tm3+. After the UV light excitation source was switched off, the bright blue long lasting phosphorescence can be observed which could last for more than 1 h in the limit of light perception of dark-adapted human eyes (0.32 mcd/m(2)). Two TL peaks at 336 K and 415 K appeared in the TL spectrum. By analyzing the TL curve the depths of traps were calculated to be 0.67 eV and 0.97 eV, respectively.Also, the mechanism was discussed in this report.

novel blue-emitting long-lasting proyphosphate phosphor Sr2P2O7:Eu2+, Y3+

By introducing the Y3+ into Sr2P2O7:Eu2+, we successfully prepared a kind of new phosphor with blue long-lasting phosphorescence by the high-temperature solid-state reaction method. In this paper, the properties of Sr2P2O7:Eu2+, Y3+ were investigated utilizing XRD, photoluminescence, luminescence decay, long-lasting phosphorescence and thermoluminescence (TL) spectra. The phosphor emitted blue light that was related to the 4f(6)5d(1)-S-8(7/2) transition of Eu2+. The bright blue phosphorescence could be observed by naked eyes even 8 h after the excitation source was removed. Two TL peaks at 317 and 378 K related to two types of defects appeared in the TL spectrum. By analyzing the TL curve the depths of traps were calculated to be 0.61 and 0.66 eV. Also, the mechanism of LLP was discussed in this report.