Synthesis,characterisation, luminescence and defect centres in solution combustion synthesised CaZrO3:Tb3+ phosphor

Tb³⁺ doped CaZrO₃ has been prepared by an easy solution combustion synthesis method. The combustion derived powder was investigated by X-ray diffraction, Fourier-transform infrared spectrometry and scanning electron microscopy techniques. A room temperature photoluminescence study showed that the phosphors can be efficiently excited by 251 nm light with a weak emission in the blue and orange region and a strong emission in green light region. CaZrO₃:Tb³⁺ exhibits three thermoluminescence (TL) glow peaks at 126 °C, 200 °C and 480 °C. Electron Spin Resonance (ESR) studies were carried out to study the defect centres induced in the phosphor by gamma irradiation and also to identify the centres responsible for the TL peaks. The room temperature ESR spectrum of irradiated phosphor appears to be a superposition of two distinct centres. One of the centres (centre I) with principal g-value 2.0233 is identified as an O^? ion. Centre II with an axial symmetric g-tensor with principal values g_=1.9986 and g_?=2.0023 is assigned to an F⁺ centre (singly ionised oxygen vacancy). An additional defect centre is observed during thermal annealing experiments and this centre (assigned to F⁺ centre) seems to originate from an F centre (oxygen vacancy with two electrons). The F centre and also the F⁺ centre appear to correlate with the observed high temperature TL peak in CaZrO₃:Tb³⁺ phosphor.     

Photoluminescence,thermoluminescence and electron spin resonance studies on Eu<Superscript>3+</Superscript> doped Ca<Subscript>3</Subscript>Al<Subscript>2</Subscript>O<Subscript>6</Subscript> red phosphors

Tricalcium aluminate doped with Eu³⁺ was prepared at furnace temperatures as low as 500°C by using the convenient combustion route and examined using powder X-ray diffraction, scanning electron microscope and photoluminescence techniques. A room-temperature photoluminescence study showed that the phosphors can be efficiently excited by UV/Visible region, emitting a red light with a peak wavelength of 616 nm corresponding to the ⁵D₀–⁷F₂ transition of Eu³⁺ ions. The phosphor exhibits three thermoluminescence (TL) peaks at 195°C, 325°C and 390°C. Electron Spin Resonance (ESR) studies were carried out to study the defect centres induced in the phosphor by gamma irradiation and also to identify the defect centres responsible for the TL process. Room-temperature ESR spectrum of irradiated phosphor appears to be a superposition of three distinct centres. One of the centres (centre I) with principal g-value 2.0130 is identified as O⁻ ion while centre II with an axially symmetric principal values g _∥=2.0030 and g _⊥=2.0072 is assigned to an F⁺ centre (singly ionized oxygen vacancy). O⁻ ion (hole centre) correlates with the TL peak at 195°C and the F⁺ centre (electron centre), which acts as a recombination centre, is also correlated to the 195°C TL peak. F⁺ centre further appears to be related to the high temperature peak at 390°C. Centre III is also assigned to an F⁺ centre and seems to be the recombination centre for the TL peak at 325°C.     

A rapid combustion process for the preparation of MgSrAl10O17:Eu phosphor and related luminescence and defect investigations

Blue-emitting europium-ion-doped MgSrAl₁₀O₁₇ phosphor, prepared using the combustion method, is described. An efficient phosphor can be prepared by this method in a muffle furnace maintained at 500 °C in a very short time of few minutes. The phosphor is characterized by powder X-ray diffraction, scanning electron microscopy, transmission electron microscopy and BET surface area measurements. Photoluminescence (PL) spectra revealed that europium ions were present in divalent oxidation state. The thermoluminescence (TL) glow curve shows two peaks at around 178 and at 354 °C. The defect centres formed in the phosphor are studied using electron spin resonance (ESR). The ESR spectrum indicates the presence of Fe³⁺ ions in the non-irradiated system. Irradiated MgSrAl₁₀O₁₇:Eu exhibits lines due to radiation-sensitive Fe³⁺ ion and a defect centre. The centre is characterized by an isotropic g-value of 2.0012 and is assigned to a F⁺ centre. The radiation-sensitive Fe³⁺ ion appears to correlate with the main TL peak at 178 °C. During irradiation an electron is released from Fe²⁺ and is trapped at an anion vacancy to form F⁺ centre. During heating, an electron is liberated from the defect centre and recombines with Fe³⁺ emitting light.     

Effects of charge compensation on red emission in CaYAl3O7:Eu3+ phosphor

Monovalent ions Li+, Na+, and K+, as charge compensators, are introduced into CaYAl3O7: M(M =Eu3+, Ce3+) in this letter. Their crystal phases and photoluminescence properties of different alkali metal ions doped in CaYAl3O7 are investigated. In addition, the influence of charge compensation ion Li+which has a more obvious role in improving luminescence intensity on CaYAl3O7: Eu3+phosphor is intentionally discussed in detail and a possible mechanism of charge compensation is given. The enhancement of red emission centered at 618 nm belonging to Eu3+is achieved by adding alkali metal ion Li+under 393-nm excitation.     

TL, OSL and ESR studies on beryllium oxide

Electron spin resonance (ESR) studies were carried out to identify the defect centres responsible for the thermoluminescence (TL) and optically stimulated luminescence (OSL) processes in BeO phosphor. Two defect centres were identified in irradiated BeO phosphor by ESR measurements, which were carried out at room temperature and these were assigned to an O⁻ ion and Al²⁺ centre. The O⁻ ion (hole centre) correlates with the main 190 °C TL peak. The Al²⁺ centre (electron centre), which acts as a recombination centre, also correlates to the 190 °C TL peak. A third centre, observed during thermal annealing studies, is assigned to an O⁻ ion and is related to the high temperature TL at 317 °C. This centre also appears to be responsible for the observed OSL process in BeO phosphor.     

Infrared emission and defect centres in Er and Yb codoped Y3Al5O12 phosphors

YAG phosphor powders doped/codoped with Er³⁺/(Er³⁺ + Yb³⁺) have been synthesised by using the solution combustion method. The effect of direct pumping into the ⁴I_11/2 level under 980 nm excitation of doped/codoped Er³⁺/Yb³⁺−Er³⁺ in Y₃Al₅O₁₂ (YAG) phosphor responsible for an infrared (IR) emission peaking at ∼1.53 μm corresponding to the ⁴I_13/2→⁴I_15/2 transition has been studied. YAG exhibits three thermally-stimulated luminescence (TSL) peaks at around 140°C, 210°C and 445°C. Electron spin resonance (ESR) studies were carried out to identify the centres responsible for the TSL peaks. The room temperature ESR spectrum of irradiated phosphor appears to be a superposition of two distinct centres. One of the centres (centre I) with principal g-value 2.0176 is identified as O⁻ ion, while centre II with an isotropic g-factor 2.0020 is assigned to an F⁺ centre (singly ionised oxygen vacancy). An additional defect centre is observed during thermal-annealing experiments and this centre (assigned to F⁺ centre) seems to originate from an F-centre (oxygen vacancy with two electrons) and these two centres appear to correlate with the observed high-temperature TSL peak in YAG phosphor.     

Synthesis, characterization, optical absorption, luminescence and defect centres in Er3+ and Yb3+ co-doped MgAl2O4 phosphors

The Er³⁺–Yb³⁺ co-doped MgAl₂O₄ phosphor powders have been prepared by the combustion method. The phosphor powders are well characterized by X-ray diffraction (XRD) and energy dispersive (EDX) techniques. The absorption spectrum of Er³⁺/Er³⁺–Yb³⁺ doped/co-doped phosphor powder has been recorded in the UV–Vis–NIR region of the electro-magnetic spectrum. The evidence for indirect pumping under 980 nm excitation of Er³⁺ from Yb³⁺ was observed in the MgAl₂O₄ matrix material. Electron spin resonance (ESR) studies were carried out to identify the defect centres responsible for the thermally stimulated luminescence (TSL) process in MgAl₂O₄:Er³⁺ phosphor. Three defect centres were identified in irradiated phosphor by ESR measurements which were carried out at room temperature and these were assigned to an O^? ion and F⁺ centres. O^? ion (hole centre) appears to correlate with the low temperature TSL peak at 210 °C and one of the F⁺ centres (electron centre) is related to the high temperature peak at 460 °C.     

Thermoluminescence and defect study of MgSiO3 ceramics

Enstatite (MgSiO₃) ceramic powders were synthesised by a low-temperature initiated self-propagating, gas-producing solution combustion process. The prepared powders were characterised by powder X-ray diffraction, scanning electron microscopy and Brunauer–Emmer–Teller specific surface area measurements. Defect centres induced by radiation were studied using the techniques of thermoluminescence (TL) and electron spin resonance (ESR). A well-resolved glow with peak at 178°C and a shouldered peak at 120°C were observed. Two defect centres were identified by ESR measurements, which were carried out at room temperature, and these were assigned to an O^? ion and F⁺ centre. The O^? ion (hole centre) appears to correlate with the main TL peak at 178°C.     

Investigation of defect centres responsible for TL/OSL in MgAl2O4:Tb

Magnesium aluminate doped with Tb³⁺ (MgAl₂O₄:Tb³⁺) was prepared by combustion synthesis. Three thermoluminsence (TL) peaks at 120, 220 and 340 °C were observed. PL and TL emission spectrum shows that Tb³⁺ acts as the luminescent centre. Optically stimulated luminescence (OSL) was observed when stimulated by 470 nm blue light.Electron spin resonance (ESR) studies were carried out to identify the defect centres responsible for the TL and OSL processes in MgAl₂O₄:Tb³⁺. Two defect centres were identified in irradiated MgAl₂O₄:Tb³⁺ phosphor by ESR measurements which was carried out at room temperature and these were assigned to V and F⁺ centres. V centre (hole centre) is correlated to 120 and 220 °C TL peaks and F⁺ centre (electron centre), which acts as a recombination centre is correlated to 120, 220 and 340 °C.     

Ba_2B_2P_2O_(10):Eu~(3+)材料的光谱特性

采用高温固相法合成了Ba2B2P2O10:Eu3+材料,并研究了材料的光谱特性。在400nm近紫外光激发下,材料的发射光谱由4组线状峰组成,峰值分别为600,618,627和660nm,分别对应Eu3+的5D0→7F1,7F2,7F3和7F4跃迁。研究了Eu3+掺杂浓度及电荷补偿剂对材料发射强度的影响,结果显示,随Eu3+掺杂浓度的增大,材料的发射强度增大,并未出现浓度猝灭效应,同时,添加电荷补偿剂可增强材料的发射强度。     

Mg3Bo3F3:Mn2+, R3+(R=Eu、Sm、Dy)的阴极射线发光

本文研究了具有长余辉发光特性的红色Mg3BO3F3:Mn2+,R3+(R=Eu,Sm,Dy)的阴极射线发光性能,以及R3+离子的掺杂对Mg3BO3F3:Mn2+的发射光谱、色坐标等的影响.     

白光LED用红色荧光粉α-Gd2（MoO4）3∶Eu的制备及其发光性能研究

以Gd2O3,MoO3,Eu2O3为原料,采用传统的高温固相反应方法制备了一种新的白光LED用红色荧光粉材料α相Gd2（MoO4）3∶Eu。利用XRD,SEM,激发和发射光谱对其进行了研究。分析了助熔剂和激活剂对样品的晶体结构,表面形貌和发光性能的影响。结果表明这种荧光粉可以被近紫外光（395nm）和蓝光（465nm）有效激发,发射峰值位于613nm（Eu^3＋离子的5^D0→7^F2跃迁）的红光,激发波长与目前广泛使用的蓝光和紫外光LED芯片相符合。因此,三价Eu离子激活的α相Gd2（MoO4）3是一种可能应用在白光LED上的红色荧光粉材料。     

Li~+掺杂Sr_2MgSi_2O_7∶Eu~(2+),Dy~(3+)长余辉材料的发光性能

采用高温固相法制备Li+掺杂Sr2Mg Si2O7∶Eu2+,Dy3+长余辉材料,对样品进行X射线衍射、扫描电镜、激发光谱、发射光谱、余辉衰减曲线和热释光曲线表征,研究了Li+掺杂对Sr2Mg Si2O7∶Eu2+,Dy3+发光性能的影响。实验结果表明:Li+掺杂对样品激发光谱和发射光谱的峰形、峰位基本没有影响,但是能改善样品的余辉性能。与未掺杂Li+的样品比较,Li+掺杂摩尔分数为2.5%样品的初始发光强度提高了1.5倍,余辉衰减常数提高了1.6倍。通过热释光曲线表征分析陷阱数量并计算了陷阱深度,分析表明,掺杂Li+能增加基质中氧空位的数量,适量增加陷阱深度,从而提高材料的发光性能。     

Eu3+摩尔浓度对Y2O2S:Eu3+,Mg2+,Ti4+红色长余辉材料光谱的影响

用高温固相法制备了Y2O2S：Eu^3 ,Mg^2 ,Ti^4 红色长余辉材料。测量了该材料的余辉曲线,余辉时间为1h以上;由X射线衍射得到晶体结构为Y2O2S.测量了不同Eu^3 摩尔浓度下的激发光谱和发射光谱,得到从^5DJ(J=0,1,2,3)^-7FJ(J=0,1,2,3,4,5)的发射谱线,并得到位于260,345,468和540nm激发峰。由于激活剂饱和效应,Y2O2S：Eu^3 ,Mg^2 ,Ti^4 发射光谱中513．6,540．1,556．4,587．3和589．3nm属于从^5D2,^5D1到^7FJ(J=0,1,2,3,4)跃迁的发射峰随Eu^3 摩尔浓度的增加相对削弱;激发谱包括位于350nm左右属于电荷转移态吸收(Eu^3 -O^2-,Eu^3 -S^2 )的激发主峰和在可见光区位于468,520和540nm属于Eu^3 离子4f-4厂吸收的激发峰。随着Eu^3 摩尔浓度的增加,位于468,520和540nm的激发峰相对增强。     

Synthesis, photoluminescence, thermoluminescence and electron spin resonance investigations of CaAl12O19:Eu phosphor

The present paper describes the synthesis of europium-doped calcium aluminate phosphor using the combustion method. An efficient blue emission phosphor can be prepared at reaction temperatures as low as 500 °C in a few minutes by this method. Characterization of the powder was done by X-ray diffraction, transmission electron microscopy, scanning electron microscope analysis and the optical properties were studied by photoluminescence spectra. Thermoluminescence (TL) studies also have been carried out on CaAl₁₂O₁₉:Eu²⁺ phosphor. The TL glow curve shows peaks at 174 and 240 °C. Defect centres formed in irradiated phosphor have been studied using the technique of electron spin resonance. Step annealing measurements indicate that one of the annealing stages of a defect centre appear to correlate with the release of carriers resulting in TL peak at 174 °C. The centre is characterized by an isotropic g-value of 2.0046 and is assigned to a F⁺ centre.     

TSL, OSL and ESR studies in ZnAl2O4:Tb phosphor

ZnAl₂O₄:Tb phosphor was prepared by combustion synthesis. ZnAl₂O₄:Tb exhibits three thermally stimulated luminescence (TSL) peaks around 150, 275 and 350 °C. ZnAl₂O₄:Tb exhibits optically stimulated luminescence (OSL) when stimulated with 470 nm light.Electron spin resonance (ESR) studies were carried out to identify defect centres responsible for TSL peaks observed in ZnAl₂O₄:Tb. Two defect centres are identified in irradiated ZnAl₂O₄:Tb phosphor and these centres are assigned to V and F⁺ centres. V centre appears to correlate with the 150 °C TSL peak, while F⁺ centre could not be associated with the observed TSL peaks.     

Photostimulated luminescence in BaX 2 :Eu 2+ (X=Br,Cl) X-ray storage phosphors

The photostimulated luminescence (PSL) effect in BaX 2 :Eu 2+ (X=Br, Cl) is comparable to that observed in BaFBr:Eu 2+ which is used in commercial X-ray storage phosphor screens. After X-irradiation the PSL stimulation spectra of BaX 2 :Eu 2+ (X=Br, Cl) single crystals are identical to the F centre absorption spectra, i.e. the F centres are the PSL-active electron trap centres. The nature of the hole centres is still unknown. The PSL response time of about 0.70 v s is within experimental error of 0.02 v s identical to the Eu 2+ radiative lifetime, whereas in BaCl 2 :Eu 2+ the PSL response time is 0.60 v s, and thus longer than the Eu 2+ radiative lifetime of 0.47 v s.     

以Eu-苯甲酸-1,10-菲咯啉为掺杂剂的SiO2,SiO2-B2O3和SiO2-B2O3-Na2O体系材料的结构及Eu3+的发光性质

用溶胶-凝胶法制备以Eu-苯甲酸-1,10-菲咯啉为掺杂剂的SiO2,SiO2-B2O3和SiO2-B2O3-Na2O为基质的发光材料.材料经1000℃退火处理后,结构十分稳定.通过激发光谱和发射光谱、红外光谱、TEM、XRD研究了基质结构对Eu3 发光性能的影响.结果显示:在589和614 nm处显示Eu3 的特征发射带,对应于Eu3 的5D0→7Fj(j=1,2)跃迁;与直接掺入EuCl3的玻璃材料相比,以Eu-苯甲酸-1,10-菲咯啉为掺杂剂的玻璃材料,虽然Eu的掺杂量较小,但Eu的发光强度较大.与以SiO2为基质的玻璃材料相比,以SiO2-B2O3为基质的玻璃材料Eu3 的发光减弱,其红外光谱显示形成Si-O-B键,说明该结构对Eu3 的发光有猝灭作用,以SiO2-B2O3-Na2O为基质的玻璃材料Eu3 的发光明显增强,其红外光谱显示不存在SiOB键的振动吸收,可能是Na取代B的位置,形成Si-O-Na键,此结构对Eu3 的发光有一定的增强作用.     

微波法合成红色长余辉发光材料Gd2O2S:Eu,Mg,Ti及其发光特性

用微波辐射法首次合成了Gd2O2S:Eu,Mg,Ti红色磷光化合物,用X射线粉末衍射(XRD)、扫描电镜(SEM)、荧光分光光度计等对合成产物进行了分析和表征.结果表明:材料的晶体结构为六方晶系,与Gd2O2S的相同.颗粒的形貌为类球形,分散性较好,尺寸在1～2 μm之间.Gd2O2S:Eu,Mg,Ti的激发光谱呈带状,激发光谱主峰位于360 nm,另外在400,422,472 nm等处也有激发峰存在;发射光谱为线状光谱,归属于Eu3 的5DJ(J=0,1,2)到7FJ(J=O,1,2,3,4)的跃迁.随着Eu浓度的增加,位于蓝绿区的586,557,541,513,498,471,468 nm处的发射峰逐渐减弱,而主峰位于627 nm处的红光发射明显增强.当Eu浓度为6 mol%时,红光发射最强.Mg,Ti共掺杂可显著改善其余辉性质.     

Infrared luminescence, thermoluminescence and defect centres in Er and Yb co-doped ZnAl2O4 phosphor

Er and Yb co-doped ZnAl₂O₄ phosphors were prepared by solution combustion synthesis and the identification of Er and Yb were done by energy-dispersive X-ray analysis (EDX) studies. A luminescence at 1.5 μm, due to the ⁴I_13/2 →⁴I_15/2 transition, has been studied in the NIR region in Er and Yb co-doped ZnAl₂O₄ phosphors upon 980 nm CW pumping. Er-doped ZnAl₂O₄ exhibits two thermally stimulated luminescence (TSL) peaks around 174°C and 483°C, while Yb co-doped ZnAl₂O₄ exhibits TSL peaks around 170°C and 423°C. Electron spin resonance (ESR) studies were carried out to identify defect centres responsible for TSL peaks observed in the phosphors. Room temperature ESR spectrum appears to be a superposition of two distinct centres. These centres are assigned to an O⁻ ion and F⁺ centre. O⁻ ion appears to correlate with the 174°C TSL peak and F⁺ centre appears to relate with the high temperature TSL peak at 483°C in ZnAl₂O₄:Er phosphor.