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采用助熔剂法生长高质量的Sm3+:YAl3(BO3)4晶体,并通过吸收光谱、荧光光谱对它的光谱特性进行表征,采用Judd–Offelt理论分析了该晶体的光谱参数。结果表明:Sm:YAl3(BO3)4晶体的t(t=2,4,6)参数分别为2=0.058×10–20,4=1.28×10–20,6=1.06×10–20。6H7/2能级的辐射寿命为520.2μs。热学性能测试表明:Sm:YAl3(BO3)4晶体具有较高的热导率,沿c轴方向是5.30W/(m K)。 相似文献
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用高温固相还原法合成了无稀土激活离子Y2O2S∶0.09Ti长余辉发光材料,研究了 Li2CO3,Na2CO3,K2CO3,K3PO4和K2HPO4等 5种助熔剂对Y2O2S∶Ti磷光体发光性能的影响。结果表明:除了 K2HPO4外,加入 Li2CO3,Na2CO3, K2CO3与 K3PO4助熔剂均可得到单相Y2O2S∶Ti晶体。发射光谱结果显示:不同助熔剂的加入并没有改变样品发射谱主峰位置(565 nm),但对其峰强度产生明显影响。助熔剂也显著改善了Y2O2S∶Ti的余辉亮度,特别是Li2CO3。10 min衰减时,Y2O2S∶Ti样品的余辉亮度从加 K2CO3助熔剂的0.15 mcd/m2增加到加Li2CO3助熔剂的10.1 mcd/m2。用紫外光激发样品,移去光源后,加Li2CO3助熔剂合成的样品在暗室中的余辉时间可持续达 5 h(0.32 mcd/m2) 。 相似文献
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用高温固相还原法合成了无稀土激活离子Y2O2S:O.09Ti长余辉发光材料,研究了Li2CO3,Na2CO3,K2CO3、K3PO4和K2HPO4等5种助熔剂对Y202S:Ti磷光体发光性能的影响。结果表明:除了K2HPO2外,加入Li2CO3,Na2CO3,K2CO3与K3PO4助熔剂均可得到单相Y2O2S:Ti晶体。发射光谱结果显示:不同助熔剂的加入并没有改变样品发射谱主峰位置(565nm),但对其峰强度产生明显影响。助熔剂也显著改善了Y202S:Ti的余辉亮度,特别是Li2CO3。10min衰减时,Y2O2S:Ti样品的余辉亮度从加K2CO3助熔剂的0.15mcd/m^2增加到加Li2CO3助熔剂的10.1mcd/m^2。用紫外光激发样品,移去光源后,加Li2CO3助熔剂合成的样品在暗室中的余辉时问可持续达5h(0.32mcd/m2). 相似文献
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《硅酸盐学报》2012,40(9)
以 K2W2O7为助熔剂,采用泡生法生长出了 Pr3+掺杂量为 5% (摩尔分数)的 KYb(WO4)2(Pr:KYbW)自激活激光晶体。X 射线衍射分析表明:生长的晶体为单斜晶系的 Pr:KYbW,晶格常数为 a = 1.065 nm、b = 1.031 nm、c = 0.753 nm、β = 130.65°。由样品的 Raman 光谱和红外光谱确认 Pr:KYbW晶体内共有 WO6和 YbO8两种畸变多面体结构,验证了晶体中钨氧桥键的存在。吸收光谱表明:在 945、975nm 处出现了 2 个最强的吸收峰,对应于Yb3+的2F7/2→2F5/2能级跃迁。晶体的上转换荧光谱表明:在 481nm 处的蓝光来自于 Pr3+的3P0→3H4能级跃迁;在 645nm 处的红光来自于 Pr3+的3P0→3F2能级跃迁。 相似文献
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采用高温固相法合成了SrMoO4:Dy3+荧光粉。在紫外光(λ=353nm)激发下,该样品发射出Dy3+的特征光谱。用热分析仪、X射线粉末衍射和荧光光谱对样品的结构、性能等进行了研究,考察了Dy的掺杂量、不同助熔剂对样品的结构和性能的影响,并讨论Dy3+浓度猝灭机理。研究表明:合成过程中添加适量的复合助熔剂Li2CO3+H3BO3,并当Dy3+的掺杂量为4%(摩尔分数)时,样品的荧光强度最强。这也说明了能量从基质MoO42–传递到Dy3+是十分有效的。 相似文献
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采用助熔剂法生长了0.5%(质量分数,下同)Cr4+:Ca2GeO4激光晶体。用X射线衍射(X-ray diffractometer,XRD)、吸收光谱及荧光光谱研究了晶体的相组成和光谱性能。XRD分析表明,获得的晶体为低温γ-Ca2GeO4相,镁橄榄石结构,空间群为Pbam。光谱分析表明:Cr4+:Ca2GeO4晶体在600~800 nm范围内的吸收峰对应Cr4+的3A2→3T1能级跃迁;晶体在1 000~1 200 nm的近红外区域的弱吸收带归因于Cr4+离子的3A2→3T2能级跃迁。室温下0.5%Cr4+:Ca2GeO4晶体荧光光谱的最强荧光发射峰值位于1 317 nm处,这归属于Cr4+的3T2→3A2能级跃迁,荧光寿命为7.9μs,发射截面为4.61×10–19 cm2。 相似文献
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通过微波溶剂热法合成梭状 NaLa(MoO4)2粉体,研究了乙二醇与水的体积比、反应温度和反应物浓度等参数对产物形貌和尺寸的影响。利用X 射线衍射仪、扫描电子显微镜、双光束紫外–可见分光光度计和荧光光谱仪对产物的物相、结构、形貌和发光性能进行了研究。结果表明:在 150 ℃微波加热 6h,可合成出尺寸(长轴为 2μm、短轴为 0.3μm)均匀的四方相四棱梭状 NaLa(MoO4)2;Eu3+掺杂后,NaLa(MoO4)2的四方相白钨矿结构没有改变;对 NaLa1–x(MoO4)2:xEu3+的荧光光谱测试表明,其在 294nm 和 393nm 波长的紫外激发下,发射波长为 615nm 的红光;Eu3+在 NaLa1–x(MoO4)2:xEu3+(x = 0.025~0.200)中没有明显的浓度猝灭。 相似文献
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Yuan Yao Yong Li Ningning Sun Jinhua Du Xiaowei Li Liwen Zhang Qiwei Zhang Xihong Hao 《Ceramics International》2018,44(6):5961-5966
[0.9(0.94Na0.5Bi0.5TiO3?0.06BaTiO3)?0.1NaNbO3]-xZnO (NBT-BT-NN-xZnO, x=0, 0.5 wt%, 1.0 wt%, 1.5 wt%, and 2.0 wt%) ferroelectric ceramics were fabricated using a conventional solid-state reaction method. The effects of ZnO content on dielectric, energy-storage and discharge properties were systematically investigated. Dielectric constant and difference between maximum and remanent polarization were significantly improved by ZnO doping. Dielectric constant of NBT-BT-NN-1.0-wt% ZnO was 3218 at 1 kHz and room temperature, i.e. one time bigger than that of pure NBT-BT-NN ceramic. As a consequence, a maximum energy-storage density of 1.27 J/cm3 with a corresponding efficiency of 67% was obtained in NBT-BT-NN-1.0-wt% ZnO ceramic. Moreover, its pulsed discharge energy density was 1.17 J/cm3, and 90% of which could be released in less than 300 ns. Therefore, ZnO doped NBT-BT-NN ceramic with a large energy-storage density and short release time could be a potential candidate for applications in high energy-storage capacitors. 相似文献
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用传统固相烧结法制备了Bi5–xEuxFe0.5Co0.5Ti3O15(BEFCT–x:x=0,0.35,0.55,0.85)陶瓷样品,对比研究了它们的结构和电磁性能。X射线衍射分析表明:掺杂未导致明显杂相,材料的剩余极化(2Pr)随掺杂量的增加呈先增加后减小的变化趋势,在Eu掺杂量为0.55时,材料的2Pr达到最大值,为11.2μC/cm2,升幅达143%,可以由Eu掺杂导致氧空位的抑制和铋氧层的破坏所形成的竞争机制解释。随Eu含量的增加,材料的剩余磁化单调上升,最大达到0.28 A m2/kg,比未掺杂时增加了2个数量级,从晶格失配、耦合增强以及共生结构等方面的综合效果解释了这一现象。材料的介电温度谱显示,Eu掺杂未明显损害材料的热稳定性,Eu掺杂所导致的介电损耗行为可能与氧空位或其他点缺陷有关联。 相似文献
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Nanosized Eu2O3 and CeO2 co-addition CoZn ceramics have been achieved via a hydrothermal method by adjusting the mol ratios of Eu and Ce. The as-prepared samples were characterized by X-ray diffraction (XRD), Transmission electron microscopy (TEM), Fourier transform infrared (FTIR), Vibrating sample magnetometer (VSM) and Infrared emission measurement (IRE-2). The particle morphologies of the as-prepared samples evolve from spherical, to self-assembled nanoparticles, and irregular nanoparticles when the mol ratios (x) of Eu and Ce was changed from 0:10 to 10:0. Correspondingly, the main phases of the as-prepared samples change from both cubic spinel CoFe2O4 and CeO2, pure cubic cerianite CeO2, to amorphous. Meanwhile, the as-prepared samples appear transformed from a ferromagnetic behavior with a saturation magnetization 66.4 emu/g to a paramagnetic behavior with a saturation magnetization of 0.55 emu/g at turning point x=3.5:6.5. While the infrared emissivity is increasing as the x from 0:10 to 3.5:6.5, reach the maximum at 3.6:6.4, and then remain stable when further increasing x till 10:0. Those may be due to the amorphous tendency rising and the particle sizes gradual decreasing with x increasing from 0:10 to 10:0. What is more important is that the solvothermal method is proved to be an efficient way to prepare CoZn nano-ceramics in this study which may open new pathways to magnetic and far infrared therapy. 相似文献
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Bin Li Guangqi Li Junhong Chen Haiyang Chen Xinming Xing Xinmei Hou Yong Li 《Ceramics International》2018,44(8):9395-9400
Elongated β–Si3N4 crystals have a significant influence on the mechanical property of Fe–Si3N4 composite. In this paper, the formation mechanism of elongated β–Si3N4 crystals in Fe–Si3N4 composite was investigated. During the preparation process, β–Si3N4 crystals developed in a spiral and layer growth mechanism in the dense areas. They kept growing from the dense areas and formed radially distributed elongated crystals with hexagonal prismatic morphology as time went on. As for the formation mechanism, the (100) crystal plane of β–Si3N4 from Si-N-O melt is mainly the vicinal crystal planes growth with different angles from the (100) crystal plane. At the later stage, the crystallization and the diffusion forces in Si-N-O molten phase decreased. However, the short range diffusion remained active and resulted in the gradient distribution of N content near the boundary. With the temperature decreasing, the disappearance of the short range diffusion implied the end of the crystallization process of the elongated β–Si3N4 crystals. 相似文献
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A robust strategy has been developed to fabricate Na2Li2Ti6O14@Li0.33La0.56TiO3 composites as promising anode materials for lithium-ion battery. Li0.33La0.56TiO3 modification does not change the basic structure of Na2Li2Ti6O14 but enhances the lattice parameter because few trivalent lanthanum ions enter the crystal lattice of Na2Li2Ti6O14. All samples show similar morphology with a narrow size distribution ranged from 100 to 500?nm. HRTEM test demonstrates that a good conductive connection between the Na2Li2Ti6O14 and Li0.33La0.56TiO3 layer is successfully formed. The electrochemical tests show that Na2Li2Ti6O14@Li0.33La0.56TiO3 (5?wt%) sample exhibits the lowest charge-transfer resistance, highest reversibility of lithium insertion/extraction, and the largest Li-ion diffusion coefficient among all samples, and then shows the best electrochemical activity. Hence, the Na2Li2Ti6O14@Li0.33La0.56TiO3 (5?wt%) electrode reveals the largest lithiation and delithiation capacities at each current density. The Na2Li2Ti6O14@Li0.33La0.56TiO3 (5?wt%) shows excellent cycling stability with a delithiation capacity of 166.8?mAh?g?1 at 500?mA?g?1 after 100 cycles. However, the corresponding delithiation capacity of pristine Na2Li2Ti6O14 is only 136.9?mAh?g?1 after 100 cycles. Li.33La.56TiO3 modification is a direct and powerful design method to enhance the delithiation and lithiation capacities and cycling stability of Na2Li2Ti6O14. 相似文献
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Huan He Junfeng Li Lei Liu Shanshan Bao Xianfei Chen Peicong Zhang Wentao Zhang Xuefei Lai 《Ceramics International》2018,44(5):5070-5075
A series of Eu3+-doped C12H18Ca3O18 phosphors were synthesized through a facile hydrothermal method and the properties of as-prepared phosphors were explored by X-ray diffractometer (XRD), scanning electron microscope (SEM), and photoluminescence (PL) spectrometer. The exploration results indicated that the C12H18Ca3O18:Eu3+ had been successfully synthesized. The morphology of C12H18Ca3O18:Eu3+ was a strip with the size of 100–4000 nm × 50–400 nm × 50–200 nm and the ratio of length to width of 2–80. The strongest emission peak of C12H18Ca3O18:Eu3+ around 620 nm was ascribed to 5Do→7F2 transition of Eu3+, and the peaks centered at 590, 653 and 694 nm respectively corresponded to 5Do →7F1, 7F3, and 7F4 transitions. C12H18Ca3O18: Eu3+ gave the red light emission, as indicated by color coordinate analysis. The photoluminescence intensity of the phosphors prepared under the Eu3+ concentration of 6% was the highest. The crystal structure of C12H18Ca3O18:Eu3+ was changed after europium ions occupied the lattice position of calcium ions. Europium ion could displace calcium arbitrarily. As a new kind of matrix, calcium citrate possesses the properties of both organic and inorganic compounds and the luminescent C12H18Ca3O18: x Eu3+ particles may be applied in biological fluorescent tags and luminescent materials. 相似文献
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Polycrystalline Ni doped Na.5Bi0.5TiO3 samples (Na0.5Bi0.5)Ti1-xNixO3, (x?=?0.5, 0.10, 0.15) have been prepared by solid state reaction. The appearance of the additional peak in X-ray diffraction pattern indicates the ordering of Ti4+ and Ni2+ ions. Polygonal grains are converted into flakes with an increase of Ni concentration. Replacement of Ti4+ by Ni2+ strongly modifies the relative contribution of two peaks in the Raman bands within 200–400?cm?1. Oxygen vacancy is observed in X-ray photoelectron spectrum to maintain charge neutrality due to aliovalent doping. Broad diffuse phase transition centered at the dielectric constant maximum indicates relaxor behaviour. Comparison between impedance and electric modulus spectrum suggests non-Debye relaxation. The ac conductivity follows the power law with the frequency exponent lies 0.52???0.72. The generation of holes by divalent Ni dopant at tetravalent Ti sites enhances optical band gap. 相似文献
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Ca5Zn4-xMgxV6O24 (x?=?0–3) microwave dielectric ceramics with low sintering temperature were synthesized via the conventional solid-state reaction. Effects of the substitution of Mg2+ for Zn2+ on crystal structures and microwave dielectric properties were investigated. XRD and Rietveld refinement showed the solid solution single phase formed when 0?≤?x?≤?2, but a few ZnO was observed when x?=?3. Meanwhile, the lattice parameters were found to decrease monotonously with Mg content increasing. The vibration modes of Raman were confirmed and the relationship with microwave dielectric properties was analyzed. Appropriate substitution of Mg2+ improved the packing fraction, the cation ordering degree, and the Y-site bond valence, contributing to high Q×f and low | τf |. However, the εr reduced with the increasing content of Mg2+ due to the decrease of ion polarizability. Finally, the best microwave dielectric properties were achieved at x?=?2 with εr =?11.0, Q?×?f?=?66,365?GHz (at 10.0?GHz), and τf =??80.4?ppm/°C. 相似文献
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Yongling Ding Aiqin Zhang Yanmin Wang Deming Wang Qian Yao Changhong Yang Panpan Lv Huadong Sun 《Ceramics International》2018,44(18):22406-22411
Highly (l00)-oriented Ni-doped Na0.5Bi0.5TiO3 (NBTNi) thin films with different A-site cation nonstoichiometry were deposited on the LaNiO3 (100)/Si substrates. We find that low levels of Na/Bi nonstoichiometry in the original composition of NBTNi films have obvious influence on the crystal structure and ferro-/dielectric properties. Na deficiency or Bi excess can lower the leakage current compared to the stoichiometric sample due to the decreased oxide-site vacancies. However, the mechanisms for the two types of films are different. That is, the mobile oxygen vacancies are tied by the Na vacancies in Na deficiency film whereas the formation of oxygen vacancies is suppressed for Bi-rich film. A good combination of ferroelectric property (Pr = 22.7?μC/cm2) and dielectric property (εr = 360 and tan?δ?=?0.11) can be achieved in Bi-rich NBTNi (Na0.5Bi0.54TNi) film. Besides, the effect of voltage and frequency on the capacitance and dielectric tunability for the Na0.5Bi0.54TNi film is investigated solely. These results show that NBT-based thin film is quite flexible in A-site nonstoichiometry, which provides a broad space for performance improvement. 相似文献