Microstructure and luminescence of transparent glass ceramic containing Er:BaF2 nano-crystals

Transparent BaF₂-SiO₂ glass ceramics doped with different content of Er³⁺ were prepared by sol-gel method. The microstructural evolution of the samples was studied with X-ray diffraction (XRD), transmission electron microscope (TEM), absorption and infrared spectra (IR). BaF₂ nano-crystals with 2-15 nm in size, depending on the crystallization temperature, distributed homogeneously among the amorphous silica matrix. The BaF₂ lattice parameters decreased with the increasing of Er³⁺ doping, indicating the incorporation of Er³⁺ into nano-crystals, which was further confirmed by energy dispersive X-ray spectroscopy (EDS) and absorption spectra analysis. The upconversion emissions of Er³⁺ emerged under the excitation at 980 nm for glass ceramic heat-treated at 800 °C.     

Red luminescence in MgO-GeO<Subscript>2</Subscript> gel glasses and glass ceramics doped with Mn ions prepared by sol-gel method

To obtain red luminants, MgO-GeO₂ gel glasses and glass ceramics doped with manganese ions were prepared by a sol-gel method and their properties were investigated by measuring X-ray diffraction (XRD), electron spin resonance (ESR), and luminescence and excitation spectra. Under UV irradiation at 254 nm, the gel glasses and glass ceramics showed red luminescence at 620–665 nm, the intensity of which became strong with increasing the heat-treatment temperature. A glass ceramic with the composition 1.0MnO-25MgO-75GeO₂ heat treated at 1000°C exhibited the strongest red luminescence at 661 nm. From the results of XRD and ESR, this luminescence is found to be due to the transition from the ⁴T_1g to the ⁶A_1g state of octahedrally coordinated Mn²⁺ ions located in MgGeO₃ polycrystals. The luminescence wavelength of the glass ceramics (∼665 nm) is long compared with Eu³⁺-containing phosphors (612 nm), therefore the glass ceramics can be expected for red luminants.     

锆硼陶瓷材料中总硼分析方法研究

对锆硼陶瓷材料中总硼的分析方法进行了研究，采用硫酸和硫酸铵及重铬酸钾氧化两步溶解法分解样品，氮气载带硼酸三甲酯蒸馏分离硼与锆（氦气流速150mL/min水溶加热，NaOH溶液吸收），材料中成分为Zr粉＋B4C粉，Zr含量≥99％（ut），经阳离子交换法除去吸收液中Na后采用ICP-AES法测定硼。方法的相对标准偏差（n=6）小于2．0％；标准加入回收率为99％。     

电化学法制备生物活性陶瓷材料研究

利用电化学方法可以在温和条件下制备生物活性陶瓷涂覆层，从而避免了高温喷涂引起的相变和脆裂，并可在形状复杂的基底上得到均匀的沉积层．因此，近年来在金属表面电沉积生物活性陶瓷涂覆层的研究方面已引起高度重视［’－‘j，然而，目前大多数文献报道所采用的恒电位方法，在沉积过程中电极表面的喊度会发生较大的变化，难以得到组分均匀的沉积层．本文报道用恒电流模式在Ti－6A14V合金表面沉积羟基磷灰石生物陶瓷涂层．1实验部分Ti－6A14V合金为电沉积基底（直径为0．65cm），辅助电极为Pt电极，参比电极采用饱和甘汞电极（SCE）．…     

稀土气相扩渗BaTiO3基PTC陶瓷的NTCR效应

采用稀土气相扩渗法制备了La改性的BaTiO3基PTC陶瓷,并对其室温电阻率的变化及温-阻效应进行了研究.结果表明,BaTiO3基PTC陶瓷经La气相扩渗后,室温电阻率从2.7×109Ω.m下降到220Ω.m,在25-500℃范围内,电阻率随温度升高单调递减,从220Ω.m降至5.8Ω.m,产生了明显的NTCR效应.结合XRD,SEM,EDAX以及介电性能测试结果分析了La气相扩渗BaTiO3基PTC陶瓷NTCR效应的形成机理,建立了NTCR效应的物理结构模型.     

La_2Ti_6O_(15)-CeTi_(21)O_(38)-PbTiO_3 ceramics formed in gaseous penetration of La-Ce into PbTiO_3 and their electric properties

PbTiO3 ceramics, which are typical ferroelectric materials, are useful in various applied fields. For example, it has a very good candidacy for piezoelectric materials for high temperature and high sensibility. In recent years, the studies on doped PbTiO3 ceramics have received consid-erable attention[1—3]. The modified PbTiO3 ceramics doped with Ca2+, Sm3+, Y3+, Ce4+ etc. have some better properties: their Curies temperature decreases, their tetragonal distortion degree de-grades and th…     

共沉淀法制备掺钕钇铝石榴石透明激光陶瓷的研究

掺钕钇铝石榴石(Nd∶YAG)多晶透明陶瓷具有良好的化学稳定性、光学性能和耐高温性能,是一种很有前途的激光工作物质。以Al(NO3).9H2O,Y2O3,Nd2O3和NH4HCO3为原料,(NH4)2SO4为静电稳定剂,正硅酸乙酯为添加剂,采用共沉淀法和反滴定方式于1100℃合成出分散均匀、团聚程度轻、YAG立方晶相的Nd∶YAG纳米前驱体粉末,经1700℃真空烧结5 h制备出Nd∶YAG透明陶瓷材料。采用TG-DTA,XRD,TEM,FT-PL和FEG-ESEM等测试手段对Nd∶YAG陶瓷材料进行了表征。研究结果表明:前驱体粉末在800℃时为无定型态,当温度达到890℃时析出大量的YAlO3(YAP)和少量的Y3Al5O12(YAG)晶体,当温度达到1012℃时就全部转化为YAG立方晶相;前驱体纳米粉末中存在团聚。Nd∶YAG陶瓷材料的激光工作波长为1.065μm,和相同组分的单晶相比存在轻微的红移现象;随着透射光波长的增加,透光率逐渐增加,在可见光区透光率约为45%,在近红外光区透光率约为58%。     

Advanced ceramics and their basic products: A challenge to the analytical sciences

The analytical characterization required in the development and in the quality control of new ceramics is discussed. For the basic substances, the problems encountered in the development of routine techniques for a direct and reliable analysis of Al₂O₃, AlN, Si₃N₄, SiC, and ZrO₂ powders are reported. Among the atomic spectrometric methods, especially slurry atomization ICP-spectrometry is described. Also the problems encountered in the development of combined procedures as required for the characterization of reference samples are presented. Methods for the direct bulk analysis of ceramics and microdistributional analysis, as they are now under development with laser-based techniques and various probe techniques, are described as well.     

堇青石蜂窝陶瓷负载锰氧化物催化分解臭氧性能

为了提高臭氧分解催化剂的实际应用能力,通过采用过渡金属锰氧化物为原料与铝胶混合涂覆到堇青石蜂窝陶瓷载体表面,制备了不同锰氧化物负载的整体式催化剂。 然后在常温常压下考察了整体式催化剂分解臭氧的性能。 通过X射线衍射(XRD)、扫描电子显微镜(SEM)、拉曼(Raman)光谱、X射线光电子能谱仪(XPS)、BET比表面积法和程序升温还原技术(H₂-TPR)对催化剂进行了表征。 研究结果表明,不同锰氧化物催化剂的活性按以下顺序排列:氧化锰八面体分子筛(OMS-2)＞MnO₂＞Mn₂O₃＞Mn₃O₄＞MnO。 相比其它锰氧化物,OMS-2负载的整体式催化剂对臭氧的反应活性最高,这可能归因于OMS-2具有较大的比表面积和较好的还原性能,从而有利于表面氧空位的生成和参与臭氧分解反应。 研究结果为提高堇青石蜂窝陶瓷负载型整体式催化剂应用于臭氧分解的性能提供了理论依据。     

Influence of Oxygen Vacancies on the Luminescence Spectra of Thin Bi4Ge3O12 Films

Luminescence spectra of thin Bi₄Ge₃O₁₂ films annealed in air and in vacuum have been investigated. It has been established that the luminescence spectra for different forms of excitation consist of three bands with maxima at 2.70, 2.40, and 2.05 eV. The relation of the bands with maxima at 2.40 and 2.05 eV to the centers that incorporate an oxygen vacancy has been shown. The separated emission bands have been interpreted.