温度梯度法生长BaY2F8晶体

应用温度梯度法生长了BaY2F8单晶.实验表明:温度梯度、降温速率、坩埚形状和尺寸是影响BaY2F8晶体生长的重要因素.温度梯度为6 ℃/mm,降温速率小于6 ℃/h,用相对较小的坩埚圆锥角度,可以获得质量较好的BaY2F8单晶体.X射线定向分析表明:温度梯度法生长的BaY2F8晶体的生长轴平行于[001]方向.结合晶体结构图分析,可认为晶体的[001]方向为结构的强键延展方向,是晶体生长的优势方向.     

Growth and Spectral Properties of Sm^（3＋）：YAl3（BO3）4 Crystal

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）。     

Er^3＋掺杂量对Er^3＋：BaY2F8晶体上转换发光性能的影响

利用温度梯度法生长了Er3＋：BaY2F8晶体。测量了样品的吸收谱、上转换荧光发射谱和上转换发光强度与激光泵浦功率的对数关系;分析了Er3＋的上转换可见发光机制和Er3＋掺量对Er3＋：BaY2F8晶体发光强度的影响。结果表明,在相同泵浦功率的980 nm光激发下的Er3＋：BaY2F8晶体的上转换发射谱中,552 n...     

Growth and Spectral Analysis of Pr^3＋-Doped KYb（WO4）2 Laser Crystal

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。     

Synthesis and Luminescence Properties of Red Long Afterglow Phosphor Y2O2S：Eu3＋,Mg2＋,Ti4＋by Sol-Gel Process

以金属硝酸盐和钛酸丁酯为原料,乙酰丙酮为螯合剂,采用溶胶–凝胶法制备了 Y2O2S：Eu3＋,Mg2＋,Ti4＋红色长余辉发光粉体。采用 X 射线衍射仪、扫描电子显微镜和荧光分光光度计对不同温度合成的样品性能进行测试与表征。结果表明：干凝胶在 600 ℃保温 2 h 生成了立方相的前驱体Y2O3：Eu3＋,Mg2＋,Ti4＋。前驱体在 1050～1150 ℃硫化后的产物为 Y2O3与 Y2O2S 的混合相,在 1 200 ℃时,硫化生成纯相的 Y2O2S：Eu3＋,Mg2＋,Ti4＋,产物平均粒径约为 150nm,1300 ℃时再次出现 Y2O3相。与高温固相法相比,溶胶–凝胶法制备的样品主激发峰出现蓝移,主发射峰位于 616nm 和 626nm处,对应于 Eu3＋的5D0→7F2跃迁;硫化温度为 1200 ℃时,样品的余辉时间为 40min。     

Modification of Optical Properties of SrAl_2O_4：Eu~（2＋）,Dy~（3＋） Phosphor by Terbium Doping

以尿素为燃料,采用快速燃烧法在650℃合成了Tb3＋掺杂的SrAl2O4：Eu2＋,Dy3＋新型长余辉光致发光材料。研究了Tb3＋掺杂对Eu2＋,Dy3＋共激活的铝酸盐长余辉发光材料的发光特性的影响。X射线衍射分析结果表明：当Tb3＋的掺杂量x=0.17%时,合成的样品结构为单相SrAl2O4单斜晶系。光致发光测试结果表明：样品的激发光谱为峰值位于345nm附近的连续宽带谱,发射光谱为峰值位于510nm左右的连续宽带谱。余辉衰减曲线结果表明：Tb3＋的适量掺杂可以提高铝酸锶的余辉性能。与SrAl2O4：Eu2＋,Dy3＋相比,掺杂Tb3＋有利于形成结晶度良好的固溶体,样品中的晶体细密紧凑,颗粒粒径约为100nm。     

Preparation and Properties of （Na0.50＋xK0.50-2xLix）Nb0.9Ta0.1O3 Lead-Free Piezoelectric Ceramics by Sol-Gel Method

采用溶胶–凝胶法制备Li＋取代（K0.5Na0.5）＋及Ta5＋取代Nb5＋的（K0.5Na0.5）NbO3陶瓷粉体,采用无压烧结工艺制备（Na0.50＋xK0.50–2xLix）Nb0.9Ta0.1O3（x=0,0.02,0.04）陶瓷样品。研究了前驱体煅烧温度对陶瓷粉体物相组成的影响。分析了不同Li＋掺杂量对样品物相组成、微观结构、体积密度及电学性能的影响。结果表明：前驱体的最佳煅烧温度为600℃,通过透射电子显微镜分析陶瓷粉体的粒径为49nm;不同Li＋掺杂量制备的（Na0.50＋xK0.50–2xLix）Nb0.9Ta0.1O3陶瓷样品均为正交相钙钛矿结构;随着Li＋掺杂量的增加,（Na0.50＋xK0.50–2xLix）Nb0.9Ta0.1O3陶瓷的体积密度先增大后减小,介电常数逐渐升高,压电常数先降低再升高,剩余极化强度逐渐升高。Li＋掺杂量x为0.04时样品的压电常数（d33=94pC/N）、相对介电常数（εr=684.33）及剩余极化强度（Pr=98.27μC/cm2）较好。     

掺铥氟化钇钡晶体的生长和光谱性能

采用提拉法生长了掺铥氟化钇钡（Tm3＋：BaY2F8,Tm：BYF）激光晶体。通过X射线衍射和光谱测试研究了晶体的相组成和光谱特征。结果表明：晶体属于单斜晶系,空间群C2/m,计算的晶胞参数：a=0.699 28 nm,b=1.052 93 nm,c=0.427 51 nm,β=99.69°。在吸收光谱中,室温下791...     

Electrical Properties of Sr0.7Ba0.3TiO3 Ceramics Doped with Nb2O5, 3Li2O · 2SiO2, and Bi2O3

The electrical properties of Sr_0.5Ba_0.3TiO₃ in the presence of Nb₂O₅ as a donor, 3Li₂O · 2SiO₂ as a sintering agent, and Bi₂O₃ as a dopant have been studied. When the compositions of the ceramics were 1 mol Sr_0.7Ba_0.3TiO₃+ 0.5 mol% Nb₂O₅+ 2 mol% 3Li₂O · 2SiO₂+ 0.2 mol% Bi₂O₃, the ceramics were sintered at 1100°C and exhibited the following characteristics: apparent dielectric constant ɛ, 25000; loss factor tan δ, 2%; insulating resistivity ρ_j, 10¹⁰Ω· cm; variation of dielectric constant with temperature Δɛ/ɛ (−25° to +85°C), +10%, −14%. ɛ and tan δ show only small changes with frequency. The study shows this ceramic can be used in multilayer technology.     

Determination of Inversion Temperature of Sb2O3-Doped BaTiO3 Positive Temperature Coefficient of Resistivity (PTCR) Ceramics by the Finite Difference Method

The effect of the cooling rate on the PTCR (positive temperature coefficient of resistivity) characteristics of 0.1 mol% Sb₂O₃-doped BaTiO₃ ceramics has been investigated. Resistances both below and above the Curie temperature were increased by slow cooling, which indicated that the resistive layer width at the grain boundary increased as the cooling rate decreased. Concentration profiles of the Ba vacancies as a function of distance from the grain boundary have been simulated by the finite difference method. The inversion temperature of the 0.1 mol% Sb₂O₃-doped BaTiO₃ system was determined to be 1160°C from the measured electrical properties and computed concentration profiles.     

Fabrication and Electrical Properties of Textured Sr0.53Ba0.47Nb2O6 Ceramics by Templated Grain Growth

Textured Sr_0.53Ba_0.47Nb₂O₆ ceramics with a relative density of >95% were fabricated using templated grain growth (TGG). Acicular KSr₂Nb₅O₁₅ template particles synthesized via a molten salt process were aligned by tape casting in a mixture of solid-state-synthesized SrNb₂O₆ and BaNb₂O₆ powders. The resulting ceramics possessed strong fiber texture along the polar axis ([001]) of the strontium barium niobate. Samples with 15.4 wt% templates attained a textured fraction of 0.82 after sintering at a temperature of 1450°C for 4 h. These materials showed peak dielectric constants of 7550 at 1 kHz, remanent polarizations of 13.2 μC/cm², saturation polarizations of 21 μC/cm² (60%–85% of the single-crystal value), piezoelectric strain coefficients of 78 pC/N (70%–85% of the single-crystal value), and room-temperature pyroelectric coefficients of 2.9 × 10⁻²μC·(cm²·°C)⁻¹ (52% of the single-crystal value). These results show that TGG is a viable option for accessing single-crystal properties in polycrystalline ceramics.     

Mechanism for the Peritectic Reaction and Growth of Aligned Grains in YBa2Cu3O6+x

It is experimentally observed that the peritectic reaction, 211 + liquid → 123, can be driven essentially to completion in 1 h at an undercooling of only ∽30°C. The kinetic data, together with the observed microstructures, are inconsistent with the normal mechanism of the peritectic reaction. It is proposed that the mechanism of the reaction involves dissolution of 211 particles into the liquid and precipitation of solid 123. The aligned grain structure is explained through sympathetic nucleation of new 123 grains on existing grains.     

垂直梯度凝固法生长PbWO_4∶(F,Y)晶体的光学性能(英文)

采用垂直梯度凝固法成功生长出直径为27mm、长为110mm,具有可控形状和形态的F-和Y3+共掺钨酸铅[PbWO4∶(F,Y)]晶体。通过透射光谱、荧光光谱、光产额、衰减时间等对钨酸铅晶体光学性能进行了表征。结果表明:与纯钨酸铅晶体相比,垂直梯度凝固法生长的PbWO4∶(F,Y)晶体在320~420nm的短波范围的光学透过率明显提高,光吸收边更尖锐;荧光光谱为350~580nm范围的宽峰,发射主峰为420nm;光产额达到50p.e/MeV(1 000ns内),发光衰减时间为5ns。     

Growth of β-Alumina (Na2O · 11Al2O3) Single Crystals by the Flux Method

The crystal-growth process and growth conditions of β-alumina (Na₂O · Al₂O₃) were investigated using the Na₂B₄O₇-Na₃AlF₆ flux method. β-Alumina (electric fusion brick) was used as both nutrient and seed. Weight loss of the flux varied widely for various runs: ≅ 10 wt% of flux evaporated at 100 h, ≅ 17 wt% at 150 h, and 43 wt% at 600 h. When β-alumina crystal was grown, only 20 wt% Na₂B₄O₇ was added to the Na₃AlF₆ flux. The linear growth rates of the β-alumina single crystal grown by an Na₃AlF₆-20 wt% Na₂B₄O₇ flux method at 1040°C and Δ t = 18°C were ≅ 1.0 × 10⁻³ mm/h ( a face) and ≅0.3 × 10⁻³ mm/h ( c face). The β-alumina single crystals grown were bounded by only c [001] and a [100] and were colorless and transparent.