白光LED用红色荧光粉的研究进展

白光LED具有工作电压低、功耗低、可靠性高、使用寿命长、环境友好和高能效等一系列优点,是未来照明光源的发展方向。利用LED技术实现白光的方法主要有3种,其中采用蓝光、紫光及近紫外LED芯片激发红、绿、蓝等三基色或多基色荧光粉得到白光LED的技术具有成本低、显色性好等优势,是白光LED的主要发展方向。红色荧光粉在调制白光的色温及改善其显色性等方面起重要作用,其制备技术是目前制约自光LED大规模应用的关键技术,亟待解决。详细介绍了白光LED用红色荧光粉的十余个主要材料体系的发光性能、基本制备方法、取得的研发进展,简单探讨了其未来发展趋势。     

白光LED用Y3-xAl5O12：Ce3x＋材料发光性能的影响因素的研究

采用高温固相法,在氢氩混合气下还原制备了白光LED用荧光材料Y3-xAl5O12：Ce3x＋。研究了助熔剂用量、焙烧温度、保温时间等因素对材料发光性能的影响。研究表明,助熔剂用量、焙烧温度、保温时间对材料的发光性能影响较大,且均存在一个最佳值,当基质原料中Ce3＋掺杂量x为0.06,助熔剂用量为6%（质量）,焙烧温度为1300℃,保温时间为4 h时所得发光材料的性能最好。XRD测试表明,所制备的材料Y2.94Al5O12：Ce03.＋06属立方晶系。荧光光谱测试表明,在365 nm紫外光激发下,材料Y2.94Al5O12：Ce03.＋06呈现白光,其形成的宽带发射光谱的主发射峰波长分别约为427 nm和472 nm。     

Fe3+掺杂Li4Ti5O12的结构及电化学性能

采用高温固相法合成Li4FexTi5-xO12(x=0.025,0.1,0.2)负极材料。通过X射线衍射、扫描电镜、充放电性能测试等对掺杂Fe3+的Li4Ti5O12材料的组成、结构、形貌进行表征,并对其电化学性能进行研究。结果表明,所合成的材料具有良好的尖晶石结构,无杂相。适当Fe3+掺杂能细化材料,提高材料的电子导电性,使材料的循环性能得到改善。Li4Fe0.025Ti4.975O12的充电容量最佳,0.1C倍率下首次充电比容量达到162.5 mA.h/g,循环性能较好。     

0.5Y2O3/Al2O3-Cu/20Mo3SiC复合材料的热变形行为及热加工图

采用真空快速热压烧结法制备了0.5Y₂O₃/Al₂O₃-Cu/20Mo3SiC复合材料,在650～950℃温度范围和0.001～10 s^-1应变速率条件下,利用Gleeble-1500D数控动态-力学模拟试验机对0.5Y₂O₃/Al₂O₃-Cu/20Mo3SiC复合材料进行热变形试验,根据试验结果绘制了其真应力-真应变曲线。根据动态材料学模型,构建了复合材料的热加工图,确定其适宜的热加工参数。结果表明：0.5Y₂O₃/Al₂O₃-Cu/20Mo3SiC复合材料的真应力-真应变曲线存在典型的动态再结晶特征,其热激活能为211.109 kJ/mol,并构建了本构方程;基于动态材料模型构造的热加工图,确定了复合材料最佳的热加工工艺参数为：变形温度为725～950℃,应变速率为0.006～0.223 s^...     

白光LED用新型红色荧光粉SrMgSi2O6:Eu3+, M(M=Gd3+, Ti4+)的合成及性质

以Na2CO3为电荷补偿剂,采用凝胶-燃烧法合成新型红色硅酸盐发光材料SrMgSi2O6:Eu3+。用X射线粉末衍射仪、荧光分光光度计等对合成产物进行分析和表征。结果表明：SrMgSi2O6:Eu3+ 的晶体结构与Sr2MgSi2O7相同,同属四方晶系。样品SrMgSi2O6:Eu3+的激发光谱在220～300 nm出现一宽带吸收,归属于O2--Eu3+之间的电荷迁移,300 nm以后出现的锐线峰为Eu3+的f-f跃迁吸收峰,其最强锐线峰位于400 nm,因而,可以被InGaN管芯产生的紫外辐射有效激发。发射光谱由两个强发射峰组成,位于592和618 nm处,分别属于典型的Eu3+的5D0→7F1和5D0→7F2跃迁。此外,研究发现：共掺Gd3+或Ti4+均能敏化Eu3+的发光,可有效提高样品的红光发射。因此,SrMgSi2O6:Eu3+, M(M=Gd3+, Ti4+)有望成为一种与InGaN管芯匹配的白光LED用红色荧光粉     

黄色发光材料Gd2O3:Dy3+的水热法合成及发光性能

以尿素为沉淀剂,采用水热方法制备Gd2O3:Dy3+黄色发光粉。通过红外光谱、X射线衍射、扫描电镜以及荧光分光光度计对水热前驱体及目标产物进行分析表征。结果表明:水热前驱体为水合碳酸钆,经900℃焙烧后得到纯立方相的Gd2O3:Dy3+。其微观形貌为针状结构,长度约为10～200μm。Gd2O3:Dy3+的激发光谱由峰值为239,279,314,353nm的一系列激发峰组成,最强峰位于279nm处;发射光谱主要由两部分组成,分别为460～500nm的蓝光和560～590nm的黄绿光的发射峰(带),最强峰位于573nm处,归属为Dy3+的4F9/2-6H13/2跃迁。Dy3+的掺杂浓度对Gd2O3:Dy3+的发光强度有着重要的影响,发光强度随着Dy3+掺杂量的增加呈现先增大后减小的趋势,掺杂浓度为0.8%时发光强度最大,其浓度猝灭主要是由电偶极-电偶极相互作用所致。     

Dy3+掺杂γ-AlON基荧光粉的合成及其发光性能

以AlN、Al2O3、Dy2O3为原料,采用高温固相反应法在1900℃、5MPa氮气气氛条件下合成AlON:Dy3+荧光粉,研究了Dy3+掺杂离子浓度对荧光粉的物相组成和发光性能的影响。结果表明:当Dy3+掺杂浓度较低时(x=0.005～0.100)合成纯的AlON相,随着Dy3+掺杂浓度的增大(x=0.125～0.250),出现微量的DyAlO3相。该荧光粉在354nm处有最强激发,其在354nm激发下呈现3个发射峰,分别位于蓝光483nm(19F9/2→6H15/2)、黄光578nm(19F9/2→6H13/2)和红光670nm(19F9/2→6H11/2),其中在578nm处黄光为最强发射。随着掺杂离子Dy3+浓度的增大,其激发峰和发射峰的强度均表现出先增大后减小的变化规律,其中当x=0.050时,发射强度最高。     

烧结助剂Y2O3和Pr6O11对Al2O3陶瓷相对密度和热导率的影响

采用高分子网络法制备混合纳米粉体,研究稀土氧化物Y2O3和Pr6O11加入量对Al2O3陶瓷相对密度和热导率的影响。采用阿基米德方法测定样品的体积密度,利用激光脉冲法测量试样的热扩散率并计算得出热导率。结果表明:两种添加剂都可以降低Al2O3陶瓷的烧结温度,提高Al2O3陶瓷的热导率,其中Y2O3的促进作用较强;当保温时间相同、烧结温度为1 500~1 650℃时,Al2O3陶瓷的相对密度和热导率都随烧结温度的升高而增大;当烧结温度相同、保温时间为30~120 min时,Al2O3陶瓷的相对密度和热导率也随保温时间的延长而增大。     

绿色/红色长余辉材料γ-Zn3（PO4）2:Mn2+,Ga3+,Ho3+的合成及光谱性质

采用高温固相法合成了Mn2+单掺杂、Mn2+,Ga3+(Ho3+)共掺杂以及Mn2+,Ga3+,Ho3+三掺杂的γ-Zn3(PO4)2。在Mn2+单掺杂的样品中,发射峰位于620nm,该样品在紫外光照射样品后,发现存在红色余辉,余辉中心与荧光中心相同。当Mn2+,Ga3+(Ho3+)共掺杂时,样品同时存在峰值位于620nm的红光发射和峰值位于507nm的绿光发射,紫外光照射样品后,样品存在红色余辉及绿色余辉。Ga3+和Ho3+在基质中自身是不发光,作为共掺杂离子,不仅可以起到调节发光中心的作用,还形成了新的深度适合的陷阱,使得绿色余辉及红色余辉性能有了很大的提高。掺杂双陷阱离子Ga3+和Ho3+,样品余辉性能最佳。     

氧化钠对CaO-Al2O3-SiO2三元系铝酸钙形成规律的影响（英文）

利用XRD、SEMEDS和DSCTG技术研究了添加Na2O的CaO-Al2O3-SiO2体系中铝酸钙的形成规律。结果表明,当Al2O3与SiO2的质量比为3.0、CaO与Al2O3的摩尔比为1.0时,在1350°C烧结后的熟料主要由12CaO·7Al2O3、2CaO·Al2O3·SiO2和2CaO·SiO2组成。熟料中12CaO·7Al2O3的含量随着Na2O的增加而增加,2CaO·Al2O3·SiO2的含量随着Na2O的增加而降低。Na2O在12CaO·7Al2O3中形成固溶体,增加了其单位晶胞体积。DSC分析表明,Na2O不仅促进了12CaO·7Al2O3的形成,而且使C12A7的形成温度降低了30°C。烧结熟料中的氧化铝溶出性能随着Na2O的增加而大幅度提高。     

Luminescence and energy transfer of Mn and Tb in Y3Al5O12 phosphors

Mn²⁺ is an excellent luminescent ion with variable color from green, yellow to red in different hosts and has been widely utilized in recent years. The luminescent intensity of Mn²⁺ in many hosts is so low that the correlative application is restricted. In the present paper, two methods, i.e. employing a charge compensator and introducing a sensitizer, were adopted to enhance the luminescence of Mn²⁺ in Y₃Al₅O₁₂ (YAG). By employing Si⁴⁺ as a charge compensator, the doping content of Mn²⁺ (x) in Y₃Mn_xAl_5−2xSi_xO₁₂ can be lifted up to 0.4. Mn²⁺ in YAG emits orange light in a broad band. The peak wavelength shifts from 586 to 593 nm with the increasing x. The luminescent intensity of Mn²⁺ reaches its maximum when x = 0.1. Co-doping Tb³⁺ into Mn²⁺ doped YAG, the sensitization effect of Tb³⁺ on Mn²⁺ was observed clearly. The resonance energy transfer from Tb³⁺ to Mn²⁺ occurs because there is a well overlapping between emission spectrum of Tb³⁺ and excitation spectrum of Mn²⁺. A reasonable explanation for the sensitization effect of Tb³⁺ on the luminescence of Mn²⁺ was brought forward.     

Preparation and characterization of Y3Al5O12:Ce and Y2O3:Eu phosphors powders by combustion process

A nickel hydroxide, Ni(OH)₂, was prepared by microwave-assisted heating technique from nickel nitrate aqueous solution and sodium hydroxide (assigned as PM). Then, the as-prepared PM was oxidized by liquid oxidation with sodium hypochlorite (assigned as PMO). Further, pure nanocrystalline nickel oxide (NiO) particles were obtained from the as-prepared PMO by calcination at 300, 400, 500, 600, 650 and 700 °C (labeled as C300, C400, C500, C600, C650 and C700, respectively). The as-prepared powders (PM and PMO) and the NiO nanoparticles were characterized by X-ray diffraction (XRD), infrared spectroscopy (IR), temperature-programmed reduction (TPR) and scanning electron microscope (SEM). The results indicated that the particle size of nickel oxide was controlled by the calcined temperature. The average crystal size of the NiO nanoparticles ranges from about 5 to 35 nm at 300–700 °C. Mechanism of nickel oxide nanocrystallite growth during thermal treatment was investigated.     

Gd~(3+)/Ga~(3+)共掺杂石榴石型Yb_3Al_5O_(12)材料的制备及热物理性能

采用柠檬酸溶胶-凝胶法制备了Gd~(3+)/Ga~(3+)双掺杂的石榴石型Yb_(3-x)Gd_xAl_(5-x)Ga_xO_(12)固溶体陶瓷材料(x=0,0.1,0.2,0.3,0.4,0.5;YGAGO)。结果表明:Gd~(3+)/Ga~(3+)共掺杂的YGAGO保持了石榴石相结构;随着Gd~(3+)/Ga~(3+)掺杂量的增加,固溶体样品的衍射峰位整体向低角度偏移;SEM形貌表明Yb_3Al_5O_(12)材料的微观形貌由纳米级晶粒和高密度晶界构成;大离子Gd~(3+)与Ga~(3+)分别对Yb_3Al_5O_(12)晶体结构中Yb~(3+)与Al~(3+)晶格位的取代,不仅因引入的点缺陷明显降低了材料的热导率,同时还造成石榴石型Yb_3Al_5O_(12)晶体结构的松弛,利于热膨胀系数的提高。随着Gd~(3+)/Ga~(3+)掺杂量的增加,晶体中点缺陷浓度不断升高,声子平均自由程不断减小,使得YGAGO的热导率在x=0.5时达到最低值(λ=1.67W/(m·K),T=1273 K),热膨胀系数达到最高值(α_1=11.71×10~(-6)K~(-1),T=1273 K)。     

Synthesis and characterization of Y3Al5O12 and ZrO2-Y2O3 thermal barrier coatings by combustion spray pyrolysis

Y₃Al₅O₁₂ and ZrO₂-Y₂O₃ (8 mol% YSZ) coatings for potential application as thermal barrier coatings were prepared by combustion spray pyrolysis. Thermal cycling of as deposited coatings on stainless steel and FeCrAlY bond coat substrates was carried out at 1000 °C and 1200 °C to determine the thermal fatigue response. Structural and morphological studies on Y₃Al₅O₁₂ and 8 mol% YSZ coatings before and after thermal cycling have been carried out. It has been noted that the coatings on FeCrAlY substrates remain intact after 50 cycles between room temperature and 1200 °C, whereas the coatings on stainless steel show some minor damage such as peeling off near the periphery after 50 cycles at 1000 °C. Thermal diffusivity values of Y₃Al₅O₁₂ and 8 mol% YSZ films were measured by using photo thermal deflection spectroscopy and the values are lower than those of coatings produced by conventional techniques such as EBPVD and APS.     

Processing, microstructure, and properties of laser remelted Al2O3/Y3Al5O12（YAG） eutectic in situ composite

Laser remelting and rapid solidification were performed in preparing the high-performance Al2O3/Y3Al5O12（YAG） eutectic in situ composite. The microstructure characteristic and solidification behavior were studied using scanning electron microscopy（SEM）, energy dispersive spectroscopy（EDS）, X-ray diffractometry（XRD） and simultaneous thermal analysis（STA）. The hardness and fracture toughness were obtained using an indentation technique. The results show that the laser remelted Al2O3/YAG composite has a homogeneous eutectic microstructure without microcrack and pore. The component phases of Al2O3 and YAG are three-dimensionally and continuously reticular connected, and finely coupled without grain boundaries, colonies and amorphous phases between interfaces. The eutectic interspacing is greatly refined with increasing the scanning rate and average is only l μm. The synthetically thermal analysis indicates that the eutectic temperature of Al2O3-YAG is 1 824 ℃, well matching the phase diagram of Al2O3-Y2O3 system. The maximum hardness reaches 19.5 GPa and the room fracture toughness is 3.6 MPa.m^1/2.     

Preparation, structure and photoluminescence of nanoscaled-Nd: Lu3Al5O12

Nd:Lu₃Al₅O₁₂ (Nd:LuAG) nano-crystalline was synthesized by co-precipitation method. Its phase transformation, structure, absorption and photoluminescence properties were studied. The Nd:LuAG polycrystalline phase is formed above 900 °C and its particle sizes are in the range of 18-36 nm. The structure of Nd:LuAG was refined by Rietveld method. The lattice parameters and the distortion of Lu³⁺-O²⁻ polyhedron in Nd:LuAG are larger than that of in pure LuAG. Because the distortion of Lu³⁺-O²⁻ polyhedron is larger than that of Y³⁺-O²⁻ polyhedron in YAG and the distance of Lu³⁺-O²⁻ is smaller than that of Y³⁺-O²⁻ in YAG, Nd³⁺ in LuAG experiences a stronger crystal field effect, which is proved by the crystal field strength and the chemical environment parameter. The absorption spectrum shows that Nd:LuAG has a broad absorption band at 808 nm with FWHM above 6 nm, which is favorable for improving laser efficiency. The fluorescence lifetime from ⁴F_3/2 → ⁴I_11/2 transition is 320 μs and longer than that of Nd:YAG. The longer lifetime is propitious to energy storage. The emission cross section at 1064 nm is 2.89 × 10⁻¹⁹ cm², taking into account the Boltzmann distribution of the excited state. The emission cross section in Nd:LuAG is also larger than that of Nd:YAG, which is useful for laser operation. All results indicate that Nd:LuAG is a promising crystal material to apply in high energy lasers.     

Eu^3＋掺杂ZnO-MgO-La2O3-B2O3基发光光纤的弹脆塑性

采用高温固相反应法制备了Eu^3＋掺杂ZnO-MgO-La203-B203基质的光致发光光纤，通过轴向拉伸试验测量了该光纤的应力-应变曲线。应用弹脆塑性理论研究了屈服面的变化和应力-应变的本构关系，计算了拉伸弹性模量、拉伸强度、拉伸最大负荷、拉伸强度的应变、断裂伸长率和材料的脆性指数。结果表明，该光纤弹性模量高于普通玻璃和大理石，接近于硬铝合金和轧制铝，其拉伸强度和所能承载的负荷都较大。     

橙红色荧光粉YPO4:Gd3+,Eu3+的制备及发光特性

采用高温固相法在1100℃下合成了橙红色荧光粉YPO₄:Gd₃₊,Eu₃₊,研究了Eu₃₊离子掺杂浓度、碱金属碳酸盐、助熔剂、敏化剂对荧光粉发光性能的影响。XRD检测结果显示：合成荧光粉为单相的YPO₄。Eu₃₊离子较佳掺杂浓度为2.5%,碱金属碳酸盐 Na₂CO₃能有效提高荧光粉的发光强度。添加助熔剂NH₄F可将荧光粉的煅烧合成温度从1100℃降低到800℃,并可促进发光中心进入晶格。Gd₃₊离子能将吸收的激发能有效传递给发光中心Eu₃₊离子,提高荧光粉的发光强度。色坐标分析显示,合成YPO₄:0.025Eu₃₊荧光粉色坐标为(0.61,0.39) ,位于橙红光的色坐标范围内。     

Melt-casting of Y3Al5O12 (YAG) ceramics by combustion synthesis under high gravity with the addition of glass

Bulk YAG-based ceramics have been prepared by melt-casting under high gravity with the addition of glass. The glass helps to reduce the porosity and grain size of the casted ceramics. In the casting process, the glass melt can feed the shrinkage cavities produced during fast solidification of YAG. With the addition of glass, the grain boundary migration of YAG is pinned and thus grain growth is limited. The effect of the glass strongly depends on its chemical composition and crystallization behavior, where a higher SiO₂ content is necessary to avoid devitrification.