Effect of Ca2+ and Mg2+ ions on the sintering and spectroscopic properties of cr-doped yttrium aluminum garnet ceramics

In this work, we investigated the effects of Ca²⁺ and Mg²⁺ ions and annealing temperature on the spectroscopic parameters of chromium-doped yttrium aluminum garnet ceramics (Cr:YAG). Samples were obtained with either a separate or a simultaneous addition of calcium and magnesium oxides. To achieve this, aqueous suspensions were prepared using Y₂O₃, Al₂O₃, Cr₂O₃, MgO, and CaO high-purity powders as raw materials. The obtained suspensions were freeze-granulated, pressed into pellets, debinded, and subjected to reactive sintering in vacuum at 1715°C for 6 h. Each material was annealed in air with temperatures between 1300 and 1700°C. Samples were also compared to Cr:YAG ceramics with the addition of silica as a sintering aid. All the materials obtained were then exposed to 445 nm excitation, and emission spectra in the visible and infrared wavelengths were recorded. The results showed that the emission spectra of Cr:YAG ceramics varied according to the annealing conditions: as-sintered samples exhibited strong emissions of around 680 nm and, after air annealing, of around 1400 nm. This phenomenon is attributed to the Cr³⁺→Cr⁴⁺ transition. Samples doped solely with MgO exhibited the highest emission intensity in the infrared region. Thus, Mg²⁺ ions provided the best conversion efficiency of chromium ions.     

YAG掺铷——钇铝石榴石激光晶体胶粘剂

YAG掺铷——钇铝石榴石激光晶体胶粘剂以丁腈改性环氧树脂,酚醛变性胺为固化剂,用于掺铷——钇铝石榴石激光晶体与钢套粘接,安装在陕西省人民医院YAG激光医用治疗机,临床应用3年,效果很好。后中国电子科技集团第二十七研究所从1990年开始用YAG激光胶粘剂粘接各类激光产品至今,经高低温试验、振动试验、冲击试验等各项性能测试及15年来工程应用证明,在各类激光产品中从未出现开裂、脱胶现象,性能稳定可靠,其粘接强度、耐冲击、耐振动、耐高低温变化、耐水、耐化学介质、耐光、耐老化性能均好,能满足生产要求,用途广泛,符合激光及各种工程应用。文中详述了酚醛变性胺固化剂的选择及该胶粘剂的性能。     

Unveiling the presence of mixed oxidation states of Europium in Li7+δEuxLa3−δZr2−δO12−δ garnet and its impact on the Li-ion conductivity

Recently, lanthanides have been employed by researchers to examine their impact on the structure and properties of Li₇La₃Zr₂O₁₂ (LLZO) garnets. In this regard, we developed Europium oxide (Eu₂O₃) doped LLZO (Li_7+δEu_xLa_3−δZr_2−δO_12−δ) solid electrolyte which demonstrates a cubic phase with the symmetry of Iad (No.230) at room temperature. In this investigation, different concentrations of Eu ranging from 0.1 to 0.6 atoms per formula unit (pfu) were doped into Li₇La₃Zr₂O₁₂ to evaluate the impact of Eu on the stability of the cubic phase and thereby the ionic conductivity. The results unveiled that upon doping Eu³⁺ ions, the Eu²⁺ state is also formed and is then self-doped into the structure in which Rietveld refinement coupled with XPS, EPR, and solid-state NMR suggests that Eu³⁺ ions most probably partially occupy Zr⁴⁺ (16a) site, the Eu²⁺ ions occupy La³⁺ (24d) site, and the Li⁺ ions occupy two different sites (24d and 96h). It was further found that such a site preference induces distortion at LaO₈ polyhedrons opening up the neck for Li-ions diffusion, thereby enhancing the ionic conductivity. Moreover, it was revealed that Li-ions probably hop from 96h to 24d and then to 96h site to generate the Li-ion movement. Overall, by introducing Eu ions into the LLZO structure, an enhanced bulk ionic conductivity of 0.30 × 10⁻³ S/cm at 298 K with a minimum electronic conductivity of 2.547 × 10⁻⁹ S/cm at 298 K was achieved.     

Bismuth-activated,narrow-band,cyan garnet phosphor Ca3Y2Ge3O12:Bi3+ for near-ultraviolet-pumped white LED application

Herein, a novel Bi³⁺-activated Ca₃Y₂Ge₃O₁₂ (CYGO) narrow-band cyan-emitting phosphor was synthesized. It can be excited from 320–420 nm, and the strongest excitation peak is located at 370 nm, which is suitable for current near-ultraviolet (NUV) chips perfectly. The full width at half maximum is at 52 nm. By analyzing the crystal structure of the sample, we infer that the Bi³⁺ ions replace the Y³⁺ site to form a highly symmetrical BiO₆ octahedron. The time-resolved photoluminescence (TRPL) spectra of CYGO: Bi³⁺ reveal that the only a single emission center exists in the host lattice. A warm white light–emitting diode (WLED) device with a low correlated color temperature (3148 K) and a high color rendering index (90.2) was fabricated by using the as-prepared sample, and the significant thermal stability of CYGO: Bi³⁺ guarantees its potential application in WLEDs. It is verified that the structure with only one crystallographic Y site for Bi³⁺ dopant occupation and highly symmetrical and dense structure is conducive to realize narrow-band emission, which will provide experience for researchers to explore more Bi³⁺-activated phosphors used for high-end lighting.     

石榴石中Cr^3＋的电子结构与晶场强度的关系

本文对掺铬的GGG(Ca,Mg,Zr),GGG,YGG和YAG四种晶体进行了自旋极化的SCC-DV-X_α计算。首次报道了它们的10Dq计算值,与实验值符合得很好,并讨论了中心离子和配位体之间的距离与该计算值的关系。还计算得到了二重态~2E_3的能量值,从而阐明了YAG_2cr~(3+)只能发射窄带荧光,而GGG(Ca,Mg,Zr):Cr~(3+)能发射强的宽带荧光的机理。     

以碳酸氢铵为沉淀剂制备纳米钇铝石榴石粉体

以碳酸氢铵为沉淀剂,硝酸盐为原料,采用沉淀法,通过仔细控制沉淀过程的工艺参数,得到了煅烧后可直接生成纯相YAG的前驱体沉淀物,前驱体经过900℃煅烧即可获得纳米YAG粉体.BET,TEM和XRD的测试结果表明纳米YAG粉体的晶粒尺寸为67～175nm,晶粒形态为球形,分散性良好.粉体达到完全致密化的最低烧结温度为1450℃.所获得的粉体经过1700℃真空烧结3h,烧结体具有一定的透明度.研究表明,这种纳米YAG粉体所具有的良好烧结活性与粉体的纳米晶粒尺寸,球形晶粒形态及极佳的分散性有关.     

运用X射线荧光光谱法对石榴石分类鉴定

本文介绍了运用X射线荧光光谱法对石榴石的化学组成元素进行剖析（定性及半定量分析）,通过化学组分的不同来对石榴石进行分类、鉴定。     

共沉淀法合成钇铝石榴石纳米粉体及透明陶瓷的制备

以硝酸铝[Al(NO3)3·H2O]和硝酸钇[Y(NO3)3·6H2O]为原料、以碳酸氢铵[NH4HCO3]为沉淀剂,硫酸铵[(NH4)2SO4]为分散剂,用共沉淀法合成钇铝石榴石(yttrium aluminum garnet,YAG)纳米粉体.用X射线衍射仪、红外光谱仪、热分析仪和场发射扫描电镜等测试手段对YAG前驱体和煅烧后的粉体进行表征.结果表明:前驱体经过1 000℃煅烧5h后已完全转变成纯立方相YAG,所得的粉体分散性好、无团聚、形状近似球形、平均颗粒尺寸约为100 nm.以该YAG粉体为原料,正硅酸乙酯[Si(OC2H5)4,TEOS]为添加剂,用真空烧结技术在1 700～1 800℃煅烧20h制备YAG透明陶瓷.YAG陶瓷样品的平均晶粒尺寸为10 μm,存在少量气孔相和杂质相.为了提高YAG陶瓷的透过率,需要进一步优化陶瓷的制备工艺.     

武安上泉石榴石矿地质特征

讨论了武安上泉石榴石矿床的埋藏特征、与围岩的接触关系、矿石特征,并通过矿石的室内选矿分析,探讨其开发利用     

激光透明陶瓷研究的历史与最新进展

由于透明陶瓷具有许多比单晶优越的性能,因此透明多晶陶瓷激光器成为近年来二极管泵浦固态激光器领域的研究焦点.目前,在Nd:YAG陶瓷激光器中,已获得高于1 kw的高激光输出功率和高于65%的斜率效率,在Yb掺杂的倍半氧化物陶瓷激光器中,实现了二极管泵浦的超快飞秒锁模激光输出以及82.4%的所有陶瓷激光器中最高的斜率效率.报道了中国近来在Nd:YAG和Yb/Nd掺杂的氧化镧钇透明陶瓷方面的研究进展,由中国科学院上海硅酸盐研究所制备的Nd:YAG陶瓷激光器最大激光输出斜率效率为23.2%,由上海大学制备的一种新的Yb:Y1.8La0.2O3陶瓷激光器最大激光输出斜率效率达到52%.