Na_3La_2(BO_3)_3∶Sm^(3+)的合成及其光谱特性

Synthesis and Spectral Characteristics of Sm ^( 3+) Doped Na_3La_2(BO_ 3)_ 3

本文采用固相反应法 ,合成了一系列掺Sm3 + 的Na3La2 (BO3) 3[Na3(La1-xSmx) 2 (BO3) 3]发光体 ,X 射线粉末衍射数据分析表明它们属于正交晶系 ,空间群为Amm 2。测量了红外光谱、荧光光谱 ,观察到在5 99nm、6 45nm处有较强的荧光发射 ,并研究了发光强度与Sm3+ 离子浓度 (x)的关系 ,确定了Sm3+ 离子在Na3La2 (BO3) 3 基质中发光的适宜浓度。

In recent years, the borate luminescence materials have received much attention owing to their low synthetic temperature and high luminescent efficiency. In order to search for the new luminescent material , the synthesis and luminescence properties of Na 3(La 1- x Sm x ) 2(BO 3) 3( x =0～0 10) were firstly reported in this paper. The samples in polycrystalline form were synthesized by the conventional solid state reaction. The mixture of Na 2CO 3,La 2O 3,Sm 2O 3 and H 3BO 3 with an excess of 5 mol% were preheating at 500℃ for 10 hours, then sintered 24 hours at 720～750℃for Na 3(La 1- x Sm x ) 2(BO 3) 3( x =0 005～0 10), and 935℃ for Na 3La 2(BO 3) 3. In the course of experiment, the purity of all samples was checked by X ray diffraction (XRD) . The single phase powder of Na 3(La 1- x Sm x ) 2(BO 3) 3 in range of 0 0～1 0mol% were obtained when repeated heat treatment caused no further changes in the X ray powder diffraction patterns. X ray diffraction analysis shows that all these compounds are isomorphous with Na 3La 2(BO 3) 3, which belongs to orthorhombic systems, space group Amm 2. This indicats that the La 3+ ions( r =0 105nm) in Na 3La 2(BO 3) 3 can be partly replaced by the smaller rare earth ions Sm 3+ ( r =0 096nm) without change of crystal structure. The infrared spectra of the compounds Na 3La 2(BO 3) 3 (a), Na 3(La 0 995 Sm 0 005 ) 2(BO 3) 3 (b) and Na 3(La 0 94 Sm 0 06 ) 2 (BO 3) 3 (c) scanned between 400～ 2 000cm -1 in the transmittance mode were measured . The results were in agreement with the characteristic values of the BO 3- 3 groups. The minor difference observed in the infrared spectra of (b) and (c) at 450～550 cm -1 might be due to the changes in the Sm and La ions and their ionic radii. The luminescent properties of Sm 3+ in Na 3La 2(BO 3) 3 host were investigated by the excitation and emission spectra at room temperature. The emission spectrum obtained for Na 3La 2(BO 3) 3∶Sm 3+ under 400nm excitation at room temperature in range of 500～750nm was shown in Fig.2(a). There were four main emission peaks at near 564, 599, 645 and 707nm, among which the intensity of the 599nm line was the highest. These emission peaks were all narrow sharp peak not broad bands. They originated from the f f transitions of Sm 3+ ions 4f electrons, which assigned to 4G 5/2 → 4H 5/2 transition between 550～570nm, 4G 5/2 → 6H 7/2 transitions between 580～610nm, 4G 5/2 → 6H 9/2 transition between 630～655nm and 4G 5/2 → 6H 11/2 transitions between 700～ 710nm , respectively. They belonged to the characteristic emission of Sm 3+ ions. The excitation spectrum for Sm 3+ 599nm emission recorded at room temperature showed lines corresponding to transitions 6H 5/2 →( 4K , 4L ) 17/2 (345nm), 6H 5/2 →( 4D , 6P ) 15/2 (362nm), 6H 5/2 → 4L 17/2 (375nm), 6H 5/2 → 4K 11/2 (400nm), 6H 5/2 → 4M 19/2 ( 6P , 4P ) 5/2 (418nm), and 6H 5/2 → 4I 13/2 ( 4I 9/2 ) (475nm). As we can see in Fig.2(b). The intensity of the transition at 400nm was found to be the highest in all the spectra. It showed that the strongest fluorescence emission at 599nm could be obtained under 400nm excitation . At room temperature, the emission spectra of Na 3(La 1- x Sm x ) 2(BO 3) 3 at different concentration were recorded by the excitation of 400nm. The relative peak heights can change with the concentration of Sm 3+ , while the peak positions remain practically unchanged. The relationship between fluorescent intensities of 599nm emission peak of Sm 3+ and ac