共沉淀法合成制备Ce^3＋掺杂Lu3Al5O12纳米粉体

用碳酸氢铵作为沉淀剂,将硝酸镥、硝酸铝和硝酸铈配成混合溶液,采用反滴定共沉淀及低温煅烧前驱体的方法制备Lu3A l5O12(Ce)纳米发光粉体.采用热分析(TG-DTA)、傅立叶红外光谱(FTIR)、X射线衍射(XRD)、透射电镜(TEM)和光致发光(PL)等分析测试方法对Lu3A l5O12(Ce)粉体制备过程中的物理化学变化及粉体的激发发射发光性能进行了研究.结果表明,采用反滴定共沉淀法制备工艺,经过1000℃煅烧2h,可以得到晶粒尺寸为30nm左右,仅有轻微团聚,单一石榴石相的Lu3A l5O12(Ce)粉体.并且在1000℃处理得到的粉体的光致发光最强.

共沉淀法制备Lu3Al5O12∶Ce陶瓷发光粉体的研究

报道了用反滴定共沉淀法及低温煅烧前驱体的方法制备Ce3＋s杂的Lu3Al5O12石榴石陶瓷发光粉体的研究。通过对实验中制备的Lu3Al5O12∶Ce前驱体和煅烧粉体进行的X射线粉末衍射（XRD）和透射电镜（TEM）的测试表征表明,在1000℃烧结热处理2h即可获得完全单一的立方相Lu3Al5O12∶Ce粉体,粉体的平均粒径-30 nm。而随烧结温度的增加,粒径有增大的趋势。在1000℃空气氛热处理的Lu3Al5O12∶0.5%Ce发光粉体具有最强的荧光发射。粉体经干压、等静压成型后,在1800℃经流动的H2气氛常压烧结保温6 h可获得半透明Lu3Al5O12∶0.5%Ce陶瓷。X射线激发下的快分量衰减时间短至十几ns,占发光成分中主要部分的慢分量为-100 ns。

Eu^(3+)掺杂Lu_3Al_5O_(12)球形荧光颗粒的合成及性能研究

以尿素为沉淀剂,通过均匀沉淀技术制备前驱体颗粒,经后续煅烧获得分散性能良好的球形(Lu_(0.95)Eu_(0.05))_3Al_5O_(12)((Lu_(0.95)Eu_(0.05))AG)荧光颗粒。通过调整尿素浓度实现了球形荧光颗粒尺寸的可控合成。在此基础上,采用FT-IR、TG/DTA、XRD、FE-SEM、TEM和PLE/PL对材料的合成、物相形成及荧光性能等进行一系列表征。分析结果表明:前驱体经较低的温度1100℃煅烧即可获得(Lu0.95Eu0.05)AG球形荧光颗粒,且该荧光颗粒具有高的理论密度,适于闪烁体材料的应用。在235 nm电荷迁移带(CTB)的激发下,(Lu_(0.95)Eu_(0.05))AG石榴石于592 nm(Eu^(3+)的~5D_0→~7F_1磁偶极子跃迁)处呈现优异的橙红光发射,其色坐标为(0.63,0.37)。该荧光颗粒的发光强度随颗粒尺寸的增大而增强,荧光寿命随颗粒尺寸的增大而缩短。球形(Lu_(0.95)Eu_(0.05_)AG石榴石颗粒有望成为一类新型荧光材料,广泛应用于照明及显示领域。

稀土掺杂Lu_3Al_5O_(12)荧光粉的发光特性及能量传递

采用高温固相法制备了Ce、Sm共掺Lu_3Al_5O_(12)荧光粉。通过X射线衍射分析、荧光光谱分析研究了样品的结构、发光特性,并通过理论计算研究了能量传递效率、能量传递的临界距离以及能量传递方式。X射线衍射分析表明所制备的荧光粉具有单一的石榴石结构;荧光光谱分析表明,在464 nm蓝光激发下,Sm^(3+)的引入可增加Lu_3Al_5O_(12)∶Ce,Sm发射光谱中红光成分,并且随着Sm^(3+)浓度的增加,Ce^(3+)发光强度逐渐减弱。计算出Ce^(3+)、Sm^(3+)之间的能量传递效率高达77.42%,确定了Ce^(3+)、Sm^(3+)之间的能量传递机制为偶极-偶极相互作用。

镥铝石榴石(Lu_3Al_5O_(12)∶Pr)晶体的生长及发光性能

用提拉法生长出了直径45 mm的Lu_3Al_5O_(12)∶1%Pr(LuAG∶Pr)石榴石闪烁晶体。测试了该晶体不同部位样品的吸收谱、激发发射光谱和多道能谱等。对晶体的吸收波段、发光峰位和激发波长及其对应的Pr离子中电子的跃迁能级进行了指认。测得LuAG∶Pr晶体在137Cs放射源激发下的闪烁衰减时间为29 ns,光产额约为10800±540photons/MeV,光致发光衰减时间为21.93 ns。LuAG∶Pr晶体样品的热释光(TSL)曲线证实晶体中存在较多的能够束缚电子的浅陷阱。

Sm^(3+)/Ho^(3+)掺杂Lu_3Al_5O_(12)基荧光粉的制备与发光性能研究

采用高温固相法制备了Sm^(3+)/Ho^(3+)掺杂Lu_3Al_5O_(12)基荧光粉。XRD结果显示:所合成的荧光粉具有单一相石榴石结构。荧光光谱分析表明,在蓝光激发下,Lu_3Al_5O_(12):Sm^(3+)样品的发射光谱的峰值波长为568nm和614nm,Sm^(3+)的最佳掺杂摩尔分数为6.3%;Lu_3Al_5O_(12):Ho^(3+)发射光谱峰值波长为549nm,Ho^(3+)样品的最佳掺杂摩尔分数为4%。在Sm^(3+)、Ho^(3+)共掺Lu_3Al_5O_(12(:Sm^(3+),Ho^(3+)荧光粉中,Sm^(3+)、Ho^(3+)均为发光中心,样品的发射光谱中同时出现单掺Sm^(3+)、Ho^(3+)的特征发射峰。可见,Lu_3Al_5O_(12):Sm^(3+),Ho^(3+)可用作暖白光LED用荧光粉。

超声喷雾共沉淀法制备的Lu_3Al_5O_(12)∶Eu^(3+)纳米粉体发光特性

采用新型超声喷雾共沉淀法技术,以Lu2O3、Eu2O3、Al(NO3)3.9H2O为原料,制备了不同浓度Eu3+离子掺杂的Lu3Al5O12纳米粉体.用X射线粉末衍射表征了获得纳米粉体的相,用扫描电镜观察了纳米粒子的形貌.测定了粉体的激发光谱、7F0-5 D2声子边带谱与发射光谱.研究了不同高温烧结温度与Eu3+掺杂浓度对纳米粒子的发光强度与粒子形貌的影响规律.研究表明,当烧结温度高于900℃时,粉体发光强度明显增强,并且随着煅烧温度的增加,发光强度有所增强.Eu3+离子的最佳掺杂浓度为5～7mol%.根据稀土离子Eu3+光学跃起矩阵元的特点,从发射光谱获得Eu3+光学跃起的J-O参量Ω2与Ω4.在Eu3+掺杂浓度均为5mol%时,其强度参量达最小,电-声子耦合最强.然后随着掺杂浓度的进一步提高,强度参量略有增加,电-声子耦合减弱.说明Eu-O键强增加,共价性增强,Eu3+的局域环境对称性降低.Ω2值低于Eu3+在玻璃与晶体基质中的情况,这是由于纳米粒子中存在着大量的缺陷以及晶体的结构畸变导致纳米粒子的对称性下降所致.

Effects of Annealing Treatments on Luminescence and Scintillation Properties of Ce:Lu_3Al_5O_(12) Crystal Grown by Czochralski Method

Lu3Al5O12 single crystals grown in pure N2 atmosphere by Czochralski method were annealed in oxidizing atmosphere （air）and reducing atmosphere （H2 ＋ N2）, respectively. Effects of annealing treatments on luminescence and scintillation properties of the crystals were investigated. The crystal annealed in air showed the highest luminescence intensity under blue light or vacuum ultraviolet excitation in comparison with that annealed in reducing flux or the as-grown crystal. Under X-ray excitation, crystal annealed in reducing atmosphere had the lowest light yield, and crystal annealed in air had the fastest decay time under ^137Cs 662 keV γ-ray excitation. Different annealing treatments resulted in different luminescence and scintillation properties, which might related with oxygen vacancies or defect existing in the crystals.

Ce^(3+),Eu^(3+)共掺Lu_3Al_5O_(12)多晶的发光特性及能量传递研究

利用高温固相反应制备了Ce3+、Eu3+共掺杂的(Ce0.01EuxLu0.99-x)3Al5O12(x=0.02%、0.5%、1%、2%)多晶粉末,并对其结构和光谱学特性,特别是Ce3+向Eu3+的能量传递问题进行了研究。X射线衍射结果显示,所制备样品具有单一的石榴石结构。利用X射线激发发射谱和光致激发发射谱研究了Eu3+掺入浓度对发光中心Ce3+和Eu3+离子发光特性的影响以及Ce3+向Eu3+的能量传递。样品的热释光谱进一步证明Ce3+向Eu3+的能量传递及其与Eu3+浓度之间的变化关系。

Synthesis and luminescent properties of Pr-doped Lu_3Al_5O_(12) translucent ceramic

Lutetium aluminum garnet （LuAG） precursors doped with different Pr^3＋ concentration （0.25at.%, 0.5at.%, 1.0at.%, 3.0at.%, 5.0at.%） were synthesized via a co-precipitation method using ammonium hydrogen carbonate as precipitant. The phase evolution and morphology of the precursor were characterized with X-ray diffractometer （XRD） and transmission electron microscopy （TEM）. The resultant LuAG：Pr^3＋ powder was sintered into translucent ceramic without any additives in vacuum at 1150 ℃ and then in nitrogen atmosphere at 1700 ℃. spectra of LuAG：Pr^3＋ powder and ceramic were measured at room temperature in vacuum ultraviolet （VUV） and ultraviolet （VU） region. For the 5d-4f transition of Pr^3＋ ions, dominant emission of ceramic samples peaking round 311 um had higher luminescence intensity. And the host absorption in ceramic samples was not as intensive as that in powder samples. The luminescent intensity of LuAG：Pr^3＋ varied with the Pr^3＋ contents and the quenching concentration was about 1.0at.% for ceramic and 3.0at.% for powder, which was much higher than 0.24at.% for LuAG：Pr^3＋ single crystals. This phenomenon showed that the ceramic had some superiority over single crystals.

制备条件对镥铝石榴石纳米粉体合成的影响

采用溶剂热法研究起始材料硝酸镥(Lu(NO_3)_3·6H_2O)和硝酸铝(Al(NO_3)_3·9H_2O)中结晶水去除前后对镥铝石榴石(LuAG)纳米粉体合成的影响;比较高温热处理对LuAG纳米粉体合成的影响;利用X射线衍射仪、红外光谱仪、透射电子显微镜分析所得粉体的物相组成、微观形貌和分散情况。结果表明,对于含结晶水的起始材料采用溶剂热法能够合成纯相的LuAG纳米粉体,颗粒尺寸为100 nm左右且具有较好的分散性;高温热处理后,纳米粉体结构趋于完整,但纳米颗粒有团聚现象。认为原材料中结晶水的去除不利于溶剂热法合成LuAG纳米粉体,而高温热处理所得的LuAG纳米粉体均已结晶。

Spectroscopic properties of vacancies and trap levels in Lu_3Al_5O_(12):Ce^(3+) crystals

In order to study the spectroscopic properties of vacancies and trap levels in Lu3Al5O12:Ce 3+(LuAG:Ce 3+)crystal,the <111>-oriented LuAG:Ce3 +crystal grown in pure nitrogen atmosphere by Czochralski method was annealed in oxidizing atmosphere (air)and reducing atmosphere(H2+N2),respectively.The excitation and emission spectra of LuAG-Ce 3+ crystal after different thermal annealing treatments were measured in the temperature range of 8:450 K,and the thermally stimulated luminescence curves of LuAG-Ce3 +crystal were characterized.It is found that the oxygen vacancies in LuAG:Ce 3+crystal are effectively eliminated through the annealing treatment in air and four trap levels are observed in as-grown LuAG:Ce 3+ crystal with temperature position peaking at 110,210,325 and 475℃,respectively.

High entropy(Y0.2Yb0.2Lu0.2Eu0.2Er0.2)3Al5O12:A novel high temperature stable thermal barrier material

Ytterbium aluminum garnet(Yb3Al5O12)is considered as a promising thermal barrier material.However,the main limitations of Yb3Al5O12 for thermal barrier applications are relative low thermal expansion coefficient and high thermal conductivity.In order to overcome these obstacles,herein,a new high entropy(Y0.2Yb0.2Lu0.2Eu0.2Er0.2)3Al5O12 ceramic was designed,and then powders and bulk were prepared through solid-state reaction method and spark plasma sintering(SPS),respectively.The thermal expansion coefficient of HE(Y0.2Yb0.2Lu0.2Eu0.2Er0.2)3Al5O12 is(8.54±0.29)×10^-6 K^-1 at 673 K–1273 K,which is about 9%higher than that of Yb3Al5O12.The thermal conductivity of HE(Y0.2Yb0.2Lu0.2Eu0.2Er0.2)3Al5O12 ceramic is 3.81 W·m^-1 K^-1 at 300 K,which is about 18%lower than that of Yb3Al5O12.Moreover,there is no reaction between HE(Y0.2Yb0.2Lu0.2Eu0.2Er0.2)3Al5O12 and thermally grown(TG)Al2O3 even at 1600℃.After annealing at 1590℃for 18 h,the average grain size of HE(Y0.2Yb0.2Lu0.2Eu0.2Er0.2)3Al5O12 increases only from 1.56μm to 2.27μm.Close thermal expansion coefficient to TG Al2O3,low thermal conductivity,good phase stability,excellent chemical compatibility with TG Al2O3 and slow grain growth rate make HE(Y0.2Yb0.2Lu0.2Eu0.2Er0.2)3Al5O12 promising for thermal barrier applications.