Effect of air annealing on the spectral properties of Ce : Y3Al5O12 single crystals grown by the temperature gradient technique

Five absorption hands, at 227, 300 340, 370 and 457nm, were observed in the optical absorption spectrum of Ce:Y3Al5O12 (Ce:YAG) crystals grown by the temperature gradient technique (TGT). The absorption bands at 227, 340, and 457 nm were identified Lis belonging to the Ce3+ -ion in the YAG crystal. A near UV optical emission band at 398nm was observed. with an excitation spectrum containing two bands, at 235 and 370nm. No fluorescence was detected under 300 nm excitation. The pair of absorption bands at 235 and 370 nm and the absorption band at 300 nm were attributed to the F- and F+-type color centers, respectively. The color centers model was also applied to explain the spectral changes in the Ce:YAG (TGT) crystal, including the reduction in the Ce 31 -ion absorption intensity, after annealing in an oxidizing atmosphere (air). (C) 2004 Elsevier B.V. All rights reserved.

Color centers and charge state change in Ce : YAG crystals grown by temperature gradient techniques

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 370 nm were observed in as-grown crystals. Changes in optical intensity of the 235 and 370 nm 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 294 nm band seems to be present in the crystals. (c) 2005 Elsevier B.V. All rights reserved.

Ce：Lu2Si2O7闪烁晶体的结构和光谱特性

采用中频感应提拉法生长出Ce：Lu：Si2O7(Ce：LPS)晶体．通过x射线粉末衍射分析，晶体结构属单斜晶系的C21m空间群·光学显微镜下可观测到晶体的(110)解理．在室温下测试了Ce：LPS晶体的吸收光谱、激发光谱和发射光谱。结果表明，Ce：LPS晶体的吸收峰只有两个，分别位于302和349nm，且与激发峰的位置一致，归因于Ce^3+的4f^1→5d^1跃迁的特征吸收所致．发射光谱具有Ce^3+典型的双峰特征，经Gaussian多峰值拟合，带状谱是由384和407nm两个发射峰叠加而成，且后者的强度

YAP：Ce闪烁晶体的光致激发荧光衰减常数测量

用波长为266nm的激光激发不同尺寸、不同掺Ce^3＋浓度的YAP：Ce闪烁晶体，测量其光致激光荧光衰减常数，测量结果表明：YAP：Ce闪烁晶体的光致荧光衰减常数约为18．2ns，且与实验晶体厚度及Ce^3＋掺杂浓度（0．1％～0．6％原子分数）无关。

Spectroscopic properties of Ce : YAP scintillation crystal grown by temperature gradient technique

Spectroscopic properties of Ce-doped yttrium orthoaluminate (Ce:YAlO3 or Ce:YAP) crystals grown by temperature gradient technique (TGT) were investigated, and the effects of the growth conditions on the properties were analyzed.. Methods of optical absorption (OA), photoluminescence (PL), photoluminescence decay (PLD), X-ray excited luminescence (XL) and cathodeluminescence (CL) were used in these investigations. The results showed that the absorption band peak at 202, 394 and 532 nm originated from F and F+ color center induced by the weak reducing growth atmosphere, green emission band near 500 ran derived from Ce3+ -Ce3+ pairs and band at 650 similar to 850 run from some unintentional impurity in crystals.

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.

红外飞秒激光诱导Ce^3＋掺杂闪烁晶体的上转换发光研究

本文研究了红外飞秒激光照射下Ce^3＋ 掺杂的YAP和LSO两种闪烁晶体的上转换发光现象.实验发现在飞秒激光泵浦下,这两种晶体的荧光均来自于Ce^3＋离子的5d-4f跃迁.荧光强度与泵浦光功率之间的依赖关系揭示了Ce^3＋：YAP和Ce^3＋：LSO晶体的上转换过程皆由三光子吸收过程所主导.分析表明,Ce^3＋：YAP和Ce^3＋：LSO晶体中的三光子吸收是三光子同时吸收.

Ce：YAP晶体中的孪晶缺陷

The twin defects in Ce:YAP were investigated by using synchrotron radiation topography and etch figures. The results show that the twins are {101} and {121} types, and the exchange of neighboring lattice parameters is considered to be the intrinsic factor for twining. Based on such analysis, the twin structure model was established. Otherwise, the growth experiment results show that the abrupt change of growth rate during shoulder formation tends to cause twining.

国产YAP：Ce闪烁晶体的相对探测能力测量

为适应在n、γ昆合脉冲辐射场中对低强度快脉冲y辐射测量的需要，近年国内新研制出实用型YAlO3：Ce（YAP：Ce）快响应无机闪烁晶体。我们使用脉冲线性电流大于1．5A的光电倍增管，分别配置这种晶体以及CeF3、NaI等晶体构成闪烁探测器，在放射性标准源场中，对晶体的相对探测能力进行测量。测量结果表明：国产新型YAP：Ce无机晶体对这1．25MeV射线的探测能力比同体积的CeF3平均高一个量级，是同体积NaI的40％左右；当晶体厚度小于2mm时，YAP：Ce与CeF2、NaI的输出比值分别大于16和44％，说明厚度越薄晶体的相对探测能力越强。