Preparation and properties of AgNiF3 crystals

Transparent single crystals of AgNiF₃ up to 3 mm on an edge have been grown by slow cooling from AgF flux. The crystals are tetragonal, space group D⁶₄-p4₂2₁2, with cell constants $\text{a}\text{= 5.56}\text{A}\text{?}$ and $\text{c}\text{= 7.86}\text{A}\text{?}$. The material has an optical absorption spectrum typical of divalent nickel in octahedral coordination with fluoride ions. A noncollinear antiferromagnetic transition at 197°K is observed.     

Crystal growth and scintillation properties of Er-doped Lu3Al5O12 single crystals

Er-doped Lu₃Al₅O₁₂ (Er:LuAG) single crystalline scintillators with different Er concentrations of 0.1, 0.5, 1, and 3% were grown by the micro-pulling-down (μ-PD) method. The grown crystals were composed of single-phase material, as demonstrated by powder X-ray diffraction (XRD). The radioluminescence spectra measured under ²⁴¹Am α-ray excitation indicated host emission at approximately 350 nm and Er³⁺ 4f-4f emissions. According to the pulse height spectra recorded under γ-ray irradiation, the 0.5% Er:LuAG exhibited the highest peak channel among the samples. The γ-ray excited decay time profiles were well fitted by the two-component exponential approximation (0.8 μs and 6-10 μs).     

Crystal growth and scintillation properties of Ce and Eu doped LiSrAlF6

Ce and Eu doped LiSrAlF₆ (LiSAF) single crystals for the neutron detection with different dopant concentrations were grown by the micro-pulling-down method (μ-PD). In Ce:LiSAF, intense emission peaks due to Ce³⁺ 5d-4f transitions were observed at approximately 315 and 335 nm in photo- and α-ray induced radio-luminescence spectra. In case of Eu:LiSAFs, an intense emission peak at 375 nm due to Eu²⁺ 5d-4f transition was observed in the radio-luminescence spectra. The pulse height spectra and decay time profiles were measured under ²⁵²Cf neutron irradiation to examine the neutron response. The Ce 3% and Eu 2% doped LiSAF showed the highest light yield of 2860 ph/n with 19 ns main decay time component and 24,000 ph/n with 1610 ns.     

Synthesis and scintillation properties of CsGd2Cl7:Ce for gamma ray and neutron detection

In this work, we report on optical and scintillation properties of a new scintillation material CsGd₂Cl₇:Ce. Crystals were grown in vacuum sealed ampoules, and the response to gamma rays and thermal neutrons was characterized. The scintillation light yield was ∼38,000 ph/MeV, and the primary decay time was 60 ns under γ-ray excitation. A thermal neutron response resulting from capture by ¹⁵⁷Gd and ¹⁵⁵Gd and subsequent emission of conversion electrons and X-rays was observed. The crystals exhibited a layered structure with cleavage planes and relatively low hygroscopicity.     

Ce:Eu:LiNbO3晶体制备及光折变性能

为了昨到光折变性能优良的晶体材料，在LiNbO3中掺进CeO2和Eu2O3，生长Ce:LiNbO3和Ce:Eu:LiNbO3单晶体，对晶体进行极化和氧化还原处理，并利用XRD、UV-VIS及二波耦合光路测试了晶体的晶格常数、吸收光谱、指数增益系数和响应时间。结果表明，Ce:Eu:LiNbO3晶体的晶格常数比Ce:LiNbO3晶体小，其吸收边比CeLiNbO3晶体红移更多，指数增益系数比Ce:LiNbO3晶体大，而响应时间比Ce:LiNbO3晶体的要短，Ce:Eu:LiNbO3是优良的光折变晶体材料。     

Crystal growth and scintillation properties of Nd-doped Lu3Al5O12 single crystals with different Nd concentrations

Nd 0.1%, 0.5%, 1% and 3% doped Lu₃Al₅O₁₂ (Nd:LuAG) single crystals were grown in the nitrogen atmosphere by the micro-pulling down (μ-PD) method. The grown crystals had a single-phase confirmed by powder XRD analysis. In absorption spectra, some weak absorption lines due to Nd³⁺ 4f-4f transitions were observed and their intensity increased with the increase of Nd concentration. When excited by ²⁴¹Am α-ray, a broad emission peak due to defects in the host lattice at 320 nm and some sharp lines due to Nd³⁺ 4f-4f transitions at wavelength longer than 400 nm were observed. The decay time profiles of Nd:LuAG under γ-ray excitation were well approximated by two exponential function of 340-760 ns and 3-5 μs for each sample. By pulse height measurement using ¹³⁷Cs, Nd 0.5%:LuAG showed the highest light yield of 7600 ± 760 photons/MeV.     

Investigations of optical and scintillation properties of Tm-doped YAlO3

Pure, 0.1, 0.5 and 1 mol% Tm-doped YAP single crystalline scintillators were grown by the μ-PD method. The XRD analysis confirmed the lattice constants decrease with the Tm concentration. In the transmittance measurement, the absorption bands due to the Tm³⁺ 4f-4f transitions were observed at 265, 360, 485, 690 and 800 nm and they were ascribed to the transition from the ³H₆ ground state to its ¹I₆, ¹D₂, ¹G₄, ³F₃ and ³H₄ excited states, respectively. Strong emission peak due to the ¹I₆-³F₄ transition of Tm³⁺ appeared at 350 nm under X-ray irradiation. The photoluminescence decay time constants related to this transition were evaluated to be from 15.3 to 17.3 μs and the scintillation decay time constants under gamma-ray excitation were estimated to be from 17.5 to 18.8 μs. The Tm 1% doped crystal exhibited the highest light yield of 15, 100 ± 1500 photons/MeV when excited by ¹³⁷Cs gamma-ray radiation.     

Ce:Fe:LiNbO3晶体光栅热固定的研究

在LiNbO3晶体中掺进CeO2和Fe2O3,以Czchralski法生长CeFeLiNbO3晶体,对晶体进行氧化还原处理.测试CeFeLiNbO3晶体的吸收光谱,发现CeFeLiNbO3晶体的吸收边相对LiNbO3晶体发生红移.氧化态的CeFeLiNbO3晶体的吸收边相对还原态的CeFeLiNbO3晶体发生紫移.采用热固定法测试CeFeLiNbO3晶体(氧化,生长,还原)的显影效率.CeFeLiNbO3晶体(还原)的显影效率低于CeFeLiNbO3晶体(氧化)的显影效率.测算并推导出热固定光栅在常温下的寿命.     

Optical properties of Sm doped Mg:LiNbO3 and Zn:LiNbO3 single crystals

Sm³⁺ doped Mg:LiNbO₃ and Zn:LiNbO₃ are grown by Czochralski method. Optical transmittance and emission spectra are measured and Judd-Ofelt theory is applied to determine phenomenological intensity parameters, oscillator strengths, radiant transition rates, total radiant lifetimes, and branching ratios. The calculations show that Judd-Ofelt parameters with the relation of Ω₄ > Ω₂ > Ω₆ exist, and ΣΩ_ξ (ξ = 2, 4 and 6) in Sm:Zn:LiNbO₃ decreases. Fluorescence spectra indicate that visible fluorescence of Sm³⁺ is made up of 570, 606, 613 and 654 nm emission bands in these crystals under 409 nm excitation.     

Influence of Ce on the luminescence properties of Er/Yb:YVO4 crystals

YVO₄ single crystals doped with Ce³⁺, Er³⁺ and Yb³⁺ ions were grown by the Czochralsski technology. The luminescence properties of Er³⁺/Yb³⁺:YVO₄ single crystals with different concentration of Ce³⁺ were studied, and the energy transfer mechanism between Er³⁺, Yb³⁺ and Ce³⁺ was discussed based on their energy level properties. The branching ratios of the ⁴I_11/2 → ⁴I_13/2 transition in different samples were calculated. The results indicate that codopants of Ce³⁺ greatly enhance the population rate of the ⁴I_13/2 level due to the fast resonant energy transfer between Er³⁺ and Ce³⁺, i.e., ⁴I_11/2(Er³⁺) + ²F_7/2(Ce³⁺) → ⁴I_13/2(Er³⁺) + ²F_5/2(Ce³⁺).     

Preparation and characterization of belt-like Sb2Se3 crystals

Orthorhombic Sb₂Se₃ belts are synthesized via a hydrothermal treatment at 200 °C and pH = 9-10 for 16 h. Transmission electron microscopic (TEM) images show that as-obtained Sb₂Se₃ belts are with a typical width in the range of 200-400 nm and length up to 20 μm. High-resolution transmission electron microscopic (HRTEM) studies reveal that the Sb₂Se₃ are oriented in the [001] growth direction. The influences of poly vinyl alcohol (PVA) and the reaction conditions on the formation of belt-like Sb₂Se₃ microstructures are discussed.     

Application of photoconductivity measurements to photodynamic processes investigation in LiYF4:Ce and LiLuF4:Ce crystals

Photoconductivity measurements are applied to the studies of photodynamic processes in LiYF₄:Ce³⁺ and LiLuF₄:Ce³⁺ crystals undergoing ultraviolet irradiation. Photoconductivity spectra were registered by means of microwave technique under irradiation at 220-320 nm at the room temperature. Photoconductivity signal appeared at ∼300 nm and monotonically increased with the shortening of wavelength. Pumping energy dependencies of photoconductivity within 225-305 nm spectral range were registered and revealed the change of the dependence degree from quadratic at longer wavelengths through linear to saturation-like at shorter ones. Numerical simulation based on four-level model of photodynamic processes was performed. Values and spectral distributions of probabilities of different types of photodynamic processes for 225-295 nm were estimated. Ce³⁺ ions excited-state photoionization cross-section spectra in both investigated materials revealed a band with a peak around 270 nm most probably corresponding to 5d-6s transition of Ce³⁺. Recombination cross-section in Ce:LiLuF₄ appeared to be two orders of magnitude higher than in Ce:LiYF₄. A complete energy level diagram of “Ce³⁺ ion-LiYF₄ crystal” system has been proposed.     

Luminescence and scintillation properties of rare-earth-doped LuF3 scintillation crystals

The Nd-doped and Er-doped LuF₃ single crystals were grown by the micro-pulling-down method to study their scintillation properties in the vacuum-ultraviolet (VUV) region. The doubly Nd–Er codoped single crystal was grown to study possibility of scintillation performance improvement by energy transfer from Er³⁺ to Nd³⁺ ions. The LiF flux was to avoid phase transition below melting temperature. The 1%Nd-doped sample showed the highest overall scintillation efficiency under X-ray excitation which was 7 times as high as that of the LaF₃:Nd 8% standard. The leading Nd³⁺ 5d–4f emission was situated at 176 nm, while the Er³⁺ 5d–4f emission for Er-doped samples was observed at 163 nm, which better matches the sensitivity of some VUV-sensitive photodetectors. The optimum Er concentration was determined to be around 1–3 mol%. No Er³⁺ 5d–4f emission was observed for the doubly Er,Nd-codoped sample due to energy transfer from the Er³⁺ to Nd³⁺ ions. Slight improvement of the light yield was observed in the doubly-doped sample with respect to the Nd-only doped one.     

Dielectric and photoconducting properties of Ga2Te3 and In2Te3 crystals

Single crystals of defect III–VI semiconductors Ga₂Te₃ and In₂Te₃ have been grown by the Bridgman method. Capacitance vs frequency measurements have been carried out from which the low frequency dielectric constants ?₅ have been determined to be 10.95 ± 0.26 and 12.3 ± 0.13 respectively. These values are compared with the high-frequency dielectric constants ?₆₀ calculated from the Phillips' model. Dark conductivity and photoconductivity have been studied as a function of annealing upto 210°C, maxinum photosensitivity being obtained for both crystals for T_anneal = 80°C. This behaviour has been related to lattice ordering through x-ray diffraction studies. Measurements of photo conductive gain indicate carrier life-times of 2 × 10^?4s and 5 × 10^?4s respectively at room-temperature.     

Spectroscopic and laser properties of SrLaGa3O7:Pr crystals

The spectroscopic properties of trivalent praseodymium (Pr³⁺) doped SrLaGa₃O₇ (SLG) crystals have been investigated at various temperatures. Absorption, emission, excitation and lifetime measurements have been performed and discussed in the framework of the Judd-Ofelt approach. Stimulated emission cross sections for the strongest transitions of Pr³⁺ ion have been calculated. Stimulated emission has been observed for the first time in Pr³⁺ doped SLG crystal, we have obtained laser operation at 488 n, at cryogenic temperatures and at 645 nm at room temperature.     

Ti-HA-BaTiO_3生物复合材料的制备与性能

为进一步提高骨修复材料的骨诱导性能,引入了BaTiO_3压电涂层。首先,通过等离子喷涂法在Ti基体上制备羟基磷灰石(HA)、Ti-HA和Ti-HA-BaTiO_3这3种生物涂层;然后,采用正交试验设计优化了喷涂工艺参数,用SEM/EDS对涂层的形貌和成分进行了表征,并通过划痕试验测试了涂层与基体的结合强度;最后,进行了细胞培养试验,用CCK-8法对细胞毒性进行了评价,并在SEM下观察了细胞的粘附形态。结果显示:细胞带有伪足,呈梭形和不规则多边形,且粘附在Ti-HA-BaTiO_3复合涂层表面;细胞伸展形态良好,涂层的细胞毒性等级不高于1级。可见,Ti-HA-BaTiO_3复合材料可以作为临床植入材料应用。     

Crystal growth and scintillation properties of Nd:CaF2

Nd³⁺ doped CaF₂ single crystal scintillator has been investigated. We tried to grow 1%, 5%, 10%, 20%, 30% and 40% Nd³⁺ doped CaF₂ single crystals by the simple melt-solidifying method. Powder X-ray diffraction (XRD) patterns were measured to identify the phase of all the samples. The XRD patterns of all the samples were similar to CaF₂. Those samples are compared in terms of their X-ray-excited radioluminescence spectra, transmittance, α-ray-excited decay time and light yield. When the X-ray is used for excitation, luminescence is observed in the VUV region. Transmittance of the crystals is more than 70% at wavelengths longer than about 180 nm. In the decay kinetics, the fast components of the samples are distributed in less than 25 ns time range and the slow components of sample are distributed in more than 90 ns. These decay times became shorter with increasing Nd³⁺ concentration. They are related to the Nd³⁺ 5d-4f VUV emission. The light yields of samples are distributed in 5-2500 photon/5.5 MeV α-ray and decrease with increasing Nd³⁺ concentration.     

Ce对Na0.5Bi0.5TiO3粉体的掺杂和扩渗改性研究

为改善Na0.5Bi0.5TiO3材料的电性能,采用溶胶-凝胶法制备了Na0.5Bi0.5TiO3粉体.通过液相Ce掺杂和气相Ce扩渗两种方法,对Na0.5Bi0.5TiO3粉体进行了改性,采用扫描电子显微镜(SEM)、X射线衍射仪(XRD)、阻抗分析仪和电阻仪对改性前后Na0.5Bi0.5TiO3粉体的组成、结构和电性能的变化进行了研究.结果表明:Ce元素的添加有助于Na0.5Bi0.5TiO3粉体电阻率的降低,而扩渗改性使电阻率的降低更为显著,经600℃扩渗的Na0.5Bi0.5TiO3粉体的电阻率由3.71×106Ω.m降至2.39×101Ω.m;稀土Ce掺杂使Na0.5Bi0.5TiO3的介电常数减小,而Ce扩渗使Na0.5Bi0.5TiO3的介电常数显著增大;Ce掺杂使粒径更加均匀,而随着气相扩渗温度的提高,晶粒粒径逐渐变大;Ce掺杂没有改变Na0.5Bi0.5TiO3的主晶相结构,但Na0.5Bi0.5TiO3粉体经Ce扩渗后,出现了单质Bi及Bi2Ti2O7、Na2Ti9O19、Na2Ti6O13的特征峰.