掺杂LiNbO3晶体的光折变性能

在LiNbO3中掺进CeO2 ,MnCO3生长Ce∶LiNbO3和Ce∶Mn∶LiNbO3晶体 ,晶体被极化和还原处理。X射线衍射仪测试晶体的晶格常数 ,采用UV -Spectrophotometer测试晶体的吸收光谱。讨论了掺杂离子对晶格常数的影响、掺杂离子在晶体中的占位及使LiNbO3晶体吸收边发生红移的机理。利用二波耦合实验测试了晶体的指数增益系数、衍射效率和响应时间 ,结果表明 :Ce∶Mn∶LiNbO3晶体的最大指数增益系数达到 2 2cm- 1 ,Ce∶LiNbO3晶体的最大指数增益系数为 17cm- 1 ;Ce∶Mn∶LiNbO3和Ce∶LiNbO3晶体的有效载流子浓度分别为 0 .4× 10 1 5cm- 3和 0 .2× 10 1 5cm- 3;最大衍射效率分别为 85 %和 72 % ;Ce∶LiNbO3和Ce∶Mn∶LiNbO3晶体的二波耦合响应时间分别为 3min和 3.5min。与Ce∶LiNbO3晶体相比 ,Ce∶Mn∶LiNbO3是性能更为优良的光折变晶体     

近化学计量比Mn:Fe:LiNbO3晶体的生长及其光学性能

采用助熔剂提拉法,从掺入0.1%(摩尔分数)Fe2O3,0.2% MnO和11.2% K2CO3的同成分LiNbO3熔体中生长出高质量近化学计量比Mn:Fe:LiNbO3晶体.采用提拉法生长了相同掺杂的同成分晶体.与同成分晶体相比较,近化学计量比晶体的紫外吸收发生紫移,红外吸收变窄.利用二波耦合光路测试了晶体的衍射效率、增益系数和响应时间.结果显示:近化学计量比晶体的增益系数和衍射效率分别达到25 cm-1和68.3%,响应时间为亚秒级.     

掺铁近化学计量比铌酸锂晶体的生长及其光学性能研究

在LiNbO3(LN)中掺进0．01％Fe3O3(质量分数)和10．9％K2O(摩尔分数)助熔剂，用顶部籽晶(TSSG)法生长近化学计量比掺铁铌酸锂(SLN：Fe)，以及采用Czochralski法生长同成分掺铁铌酸锂(CLN：Fe)。测试了晶体的晶格常数、吸收光谱和红外光谱。Li^ 取代反位铌(NbLi^4 )和占据锂空位，使SLN：Fe晶体的晶格常数变小。SLN：Fe晶体的吸收边相对于CLN：Fe晶体发生了紫移。SLN：Fe晶体的OH吸收峰移到3466cm^—1。利用二波耦合光路测试了晶体的指数增益系数和响应时间，计算了有效裁流子浓度。测试结果表明：SLN：Fe晶体的指数增益系数达到28cm^—1，而CLN：Fe晶体的指数增益系数为18cm^—1；SLN：Fe晶体的响应速度比CLN：Fe晶体提高了1个数量级。     

Zn:Ce:Fe:LiNbO_3晶体的光折变异常温度特性

在LiNbO3(LN)中掺入摩尔分数为2%的Zn,质量分数(下同)为0.1%的Ce和0.03%的Fe,采用提拉法生长具有不同摩尔比n(Li)/n(Nb)=0.94、1.10、1.25、1.40的Zn:Ce:Fe:LiNbO3晶体。采用二波耦合光路测试晶体的指数增益系数,利用四波混频光路测试晶体的位相共轭性能。随着n(Li)/n(Nb)增加,Zn:Ce:Fe:LiNbO3晶体指数增益系数和响应速率增加,位相共轭反射率增加。研究Zn:Ce:Fe:LiNbO3晶体光折变温度效应时发现:在55、70℃和110℃,在指数增益系数(Γ)–温度(T)曲线和位相共轭反射率(R)–T曲线上出现峰值,即晶体的指数增益系数和位相共轭反射率增加。采用结构相变解释了Zn:Ce:Fe:LiNbO3晶体的异常温度特性。     

近化学计量比Cu:Fe:LiNbO3晶体的生长及蓝光优化光折变性能

以K2O为助溶剂在LiNbO3中掺入0.15%(质量分数,下同)CuO,0.03%和0.05%Fe～03,用顶部籽晶溶液生长法生长近化学计量比Cu:Fe:LiNbO3晶体.以Ar+激光器的488nm激光为光源测试Cu:Fe:LiNbO3晶体的光激载流子类型,采用二波耦合光路测试了晶体的光折变存储性能,并与633nm红光...     

反钙钛矿结构锰氮化合物奇特的热膨胀性质(英文)

通过变温X射线衍射技术研究了反钙钛结构Mn3XN(X=Ga,Zn,Sn,Cu)化合物的热膨胀性质.随着温度的升高,此类材料在磁相变附近有时会伴随人的品格收缩,即负热膨胀效应.尽管如此,晶格收缩并不总是发生,如:Mn3ZnN,Mn3CuN,Mn3SnN.对这种独特的热膨胀性质与X位 置元素价电子数之间的关系进行了讨论.结果表明:3价元素更有利于此类化合物产生负热膨胀效应.通过X位置无素掺杂,可调控此类材料的负热膨胀系数和温区.Mn3Zn0.5Ge0.5N的负热膨胀系数可达-7.15×10-6/K,温区扩展到100K左右.此外,还发现Mn3GaN和Mn3Zn0.7Sn0.3N在室温附近, 晶胞常数随温度的升高几乎保持不变,显示为近零膨胀.     

In:Fe:Cu:LiNbO_3晶体光损伤阈值和非挥发性全息存储

在LiNbO3(LN)中掺入摩尔分数分别为0,0.25%,1.5%,1.75%的In2O3、质量分数为0.1%的Fe2O3和0.05%的CuO,用提拉法生长了系列 In:Fe:Cu:LiNbO3(In:Fe:Cu:LN)晶体.采用Sanarmont补偿法和透射光束图像畸变法,测试In:Fe:Cu:LN晶体的光损伤阈值,基于Scalar表达式,讨论了晶 体光损阈值变化的机理.结果表明:3%In:0.1%Fe:0.05%Cu:LN晶体光损伤阈值比LN晶体高2个数量级,3%In3+达到阈值浓度.采用0.1%Fe:0.05%Cu:LN 晶体和0.5%In:0.1%Fe:0.05%Cu:LN晶体作为存储介质,Fe2+/Fe3+作为浅能级,Cu+/Cu2+作为深能级,以氪离了激光(蓝光)作开关光,氦-氖激光(红光)作为记录光,完成双光子固定非挥发性存储实验.实验表明:0.5%1n:0.1%Fe:0.05%Cu:LN晶体存储记录速度比Mn:Fe:LN晶体提高1个数量级.     

掺镁近化学计量比LiTaO3晶体的生长及光学性能

在同成分LiTaO3熔体中掺入一定剂量的K2O,采用顶部籽晶提拉法生长掺镁近化学计量比LiTaO3晶体.对晶体分别进行光谱分析,畴结构和抗光损伤阈值的测定.结果表明:与同成分掺镁LiTaO3晶体相比较,其紫外吸收边出现明显蓝移,红外吸收峰变弱.腐蚀晶片的晶相显微镜观察结果表明:掺镁近化学剂量比晶体的畴结构是较为规则的六边形;晶体的抗光致散射能力明显提高.     

Zn2+掺杂Mn:Fe:LiNbo3晶体的特性和非挥发性全息存储

在铌酸锂LiNbo3(LN)中掺入摩尔分数为0.1%MnO,质量分数为0.03?2O3和摩尔分数分别为1%,3%和7%ZnO,用提拉法生长Zn:Mn:Fe:LN晶体.测试了晶体的红外光谱,发现7%Zn:Mn:Fe:LN晶体 OH-吸收峰位置移到3 529 cm-1.用光斑畸变法测量晶体的抗光损伤能力.结果表明:7%Zn:Mn:Fe:LN晶体的抗光损伤能力比Ma:Fe:LN晶体提高1个数量级以上.探讨了Zn:Mn:Fe:LN晶体OH-吸收峰移动和抗光致散射能力增强的机理.以He-Ne激光作记录光,高压汞灯紫外光作开关光,用双光子固定法测量了Zn:Mn:Fe:LN晶体的二波耦合衍射效率,以Mn:Fe:LN和1%Zn:Mn:Fe:LN晶体作为存储介质实现了非挥发性存储. 体.测试了晶体的红外光谱,发现7%Zn:Mn:Fe:LN晶体 OH-吸收峰位置移到3 529 cm-1.用光斑畸变法测量晶体的抗光损伤能力.结果表明:7%Zn:Mn:Fe:LN晶体的抗光损伤能力比Ma:Fe:LN晶体提高1个数量级以上.探讨了Zn:Mn:Fe:LN晶体OH-吸收峰移动和抗光致散射能力增强的机理.以He-Ne激光作记录光,高压汞灯 外光     

Mg:Mn:Fe:LiNbO3晶体的全息存储性能

在同成分铌酸锂晶体中掺入0.03?2O3和0.1%MnO2(质量分数),分别掺入0,1%,3%,4.5%,6%的MgO(摩尔分数),用提拉法生长了一系列Mg:Mn:Fe:LiNbO3晶体.检测了Mg:Mn:Fe:LiNbO3晶体的红外光谱和抗光损伤能力.掺0,1%,3%,4.5%Mg的Mg:Mn:Fe:LiNbO3晶体的OH-红外振动峰位于3484cm-1,而掺6%Mg的Mg:Mn:Fe:LiNbO3晶体红外振动峰移到3 535gm-1.采用波长为632nm的He-Ne激光器作为光源,通过二波耦合方法测试晶体的全息存储性能.结果表明:Mg:Mn:Fe:LiNbO3晶体的写入时间和动态范围随掺镁量的增加而显著减小,而光折变灵敏度略有上升,抗光损伤性能增强,其中掺镁量为3%Mg:Mn:Fe:LiNbO3晶体更适合作为全息存储介质.     

In:Ce:Mn:LiNbO3晶体的全息存储性能

原料采用固液同成分配比,在LiNbO3（LN）晶体中掺入质量分数为0．1％CeO2和0．015％MnCO3,摩尔分数分别为0,1％,2％和3％的In,用提拉法生长In：Ce ：Mn ：LN晶体。测试了In ：Ce ：Mn ：LN晶体的红外透射光谱和抗光损伤能力。结果表明：3％In ：Ce ：Mn ：LN晶体的OH振动吸收峰紫移到3508cm^-1位置;其抗光损伤能力比Ce ：Mn ：LiNgO3晶体提高2个数量级以上。利用二波耦合光路测试晶体的写入时间（τw）、擦除时间（τc）和衍射效率（η）,计算晶体的动态范围（M^#）,研究In^3＋掺量对Ce ：Mn ：LN晶体光折变性能的影响。结果表明：In ：Ce ：Mn ：LN晶体是比Ce ：Mn ：LN晶体综合性能更好的全息存储材料。     

稀土掺杂对绿色荧光粉BaAl12O19:Mn性能的影响

研究了Mg，La，Ce掺杂对BaAO19：Mn晶体结构和发光性能的影响。晶体结构的研究结果发现：La、Ce取代了部分Ba的晶格位置，Mg和Mn取代了部分Al的晶格位置，Ce和La对Ba的取代使得BaAl12O19：Mn晶胞体积减小，Mg的掺杂使得BaAl12O19：Mn晶胞体积增大。发光性能的测试结果表明，在一定的浓度范围内，Mg，La，Ce都有效地提高了BaAl12O19：Mn在真空紫外下的发光强度。     

Optical dispersion and bandgap of pure and Mn-doped 0.92Na0.5Bi0.5TiO3-0.08K0.5Bi0.5TiO3 lead-free single crystals

Optical properties of lead-free ferroelectric pure and Mn-doped 0.92Na_0.5Bi_0.5TiO₃-0.08K_0.5Bi_0.5TiO₃ (NBT-8KBT) single crystals have been investigated systematically. Refractive index and extinction coefficient were measured and the critical parameters are obtained by modified Sellmeier dispersion equations and single-oscillator dispersion relation. The decline of refractive index for Mn:NBT-8KBT could be related to the lattice distortion of the Mn ions doping. High transmittance (>70%) over the transparent region (>400 nm) was found in the pure NBT-8KBT, higher than that of Mn:NBT-8KBT, which could be caused by the increase of domain wall density. An about 100 nm red-shift of absorption edge was observed in the Mn:NBT-8KBT single crystal, which is located in the visible region. Optical bandgap energies calculated through Tauc equation and a large bandgap difference of 2.96 and 2.62 eV occurs in the NBT-8KBT and Mn:NBT-8KBT, respectively, which illustrates the modulation of the band structures by Mn doping.     

Dielectric and Pyroelectric Properties of 〈111〉-Oriented Fe-Doped 0.62Pb(Mg1/3Nb2/3)O3–0.38PbTiO3 Single Crystals

Fe-doped 0.62Pb(Mg_1/3Nb_2/3)O₃–0.38PbTiO₃ (PMN–0.38PT) single crystals were grown by a modified Bridgman technique. Two kinds of single crystals with different iron ion molar ratios, (i) 0.2 mol% and (ii) 1.0 mol%, were obtained. The effect of doping iron ions on the dielectric and pyroelectric properties of the 〈111〉-oriented PMN–0.38PT single crystals was examined. The temperature of the permittivity maximum ( T _m) exhibits no dispersion behavior and decreases with increasing doping concentration. The dielectric loss of the 0.2 mol% Fe-doped PMN–0.38PT single crystal is much lower than that of the high dopant content crystal (1.0 mol%) and undoped crystal, which makes it possess excellent pyroelectric performance. By a dynamic method, the measured pyroelectric coefficient and detectivity figure of merit ( F _D) of 0.2 mol% Fe-doped PMN–0.38PT single crystal are 439 μC/m²·K and 56.3 μPa^−1/2, respectively, both better than those of widely used pyroelectric single crystal LiTaO₃. The results imply that the single crystal is a promising candidate for infrared detectors and other pyroelectric applications. The mechanism of doping effect was also discussed based on the principles of crystal chemistry.     

Transition metal doped ZnO nanoparticles with enhanced photocatalytic and antibacterial performances: Experimental and DFT studies

Transition metal doped ZnO (TM-ZnO) nanoparticles with 3% dopant content are successfully prepared via a simple solvothermal route. This work highlights Mn, Fe, Co, Ni or Cu ions as the dopant transition metals. The as-prepared samples are wurtzite phase ZnO crystals, and the average sizes of undoped ZnO and TM-ZnO nanoparticles range from 200 nm to 400 nm. XPS studies confirm that the transition metal ions are successfully doped into the crystal lattice of ZnO. The band gaps of the undoped ZnO and TM-ZnO crystals are calculated by using UV-DRS spectroscopic measurements. The visible light response of ZnO nanomaterials is improved by doping transition metal ions. For investigating the influence of transition metal doping on the photocatalytic performance of ZnO, the photodegradation rate of methylene blue (MB) is investigated under simulated sunlight irradiation. The photocatalytic properties of ZnO doped with transition metals are improved at different degrees, among which Cu-doped ZnO exhibits the best photocatalytic performance. Based on density functional theory (DFT) calculation result, a possible photocatalytic mechanism is proposed. Furthermore, the antibacterial performance of Cu-doped ZnO is investigated by selecting E. coli, under simulated sunlight irradiation and remarkable sterilization of E. coli is achieved.     

二氧化碳逆水煤气变换催化剂制备与性能

CO_2由于热力学稳定性和动力学惰性,难以高效活化。采用并流沉淀法制备锆酸钡(BaZrO_3)催化剂并用于逆水煤气变换反应,结合物化表征和性能评价考察离子掺杂对催化活性、催化剂结构和还原性能的影响以及水热处理对催化剂结构和性能的影响。结果表明,过渡金属离子掺杂BaZrO_3催化剂产生晶格氧空位,提高CO_2转化率,以Mn离子掺杂的催化剂性能最好。晶格掺杂不会改变催化剂晶相结构,但增强晶格氧迁移能力,促进催化剂容易还原,进而显著提高逆变换催化活性。催化剂经水热处理可消除游离杂相,产物选择性提高至99.4%。优化条件下,Mn掺杂BaZrO_3催化剂上CO_2转化率大于48%,CO选择性大于99%,催化剂稳定性好,具有良好的应用前景。     

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...     

Dielectric and thermal expansion properties of LHPG grown potassium lithium niobate single crystals

Compositions of potassium lithium niobate K₆Li_4+xNb₁₀O₃₀ (x for excess mole % of Li₂O) with tetragonal tungsten bronze structure were prepared as crystal fibers by the Laser Heated Pedestal Growth technique. The lattice constants of KLN were measured by using X-ray diffraction and typical values for a = 12.5703 ± 0.0018 and c = 3.9485 ± 0.0012 were measured. This paper reports the dielectric permittivity measurements on single crystal along the a- and c- axis in the temperature range of 90-450K and frequency range of 10²-10⁵ Hz. The dielectric permittivity at room temperature along a- and c- axis was 430 and 330 respectively. Mechanism for the low temperature dielectric relaxation will be discussed. Thermal expansion behavier in the a- and the c-direction will also be reported.