摘要
硅铝酸盐由于其化学性质稳定、原材料易得,是发光材料的一种有效基质,所以受到广泛关注。其中,硅铝酸锶(Sr_2Al_2SiO_7)属于四方晶系,具有稳定的晶体学结构。Sm^(3+)作为一种常用的激活剂,其特征峰在波段300～750 nm内都有分布,有些特征激发峰位于近紫外光区,在近紫外区有强的吸收。因此,以Sr_2Al_2SiO_7为基质、 Sm^(3+)为激活剂可以制备出符合LED要求的红色荧光粉。本工作采用高温固相法合成一系列Sr_(2-x-y)Al_2SiO_7∶x%Sm^(3+),y%Li^+荧光粉。通过X射线衍射(XRD)、光致荧光光谱(PL)、绝对量子效率测量系统对样品的晶体结构、发光特性以及内量子效率进行表征和测量,并且对样品的XRD进行精修,色纯度计算。结果表明:合成样品均为单相Sr_2Al_2SiO_7,掺杂Sm^(3+)和电荷补偿剂Li^+后,没有引起相变。相对于其他阳离子Sm^(3+)(r=1.079Å)、 Li^+(r=0.920Å)的半径与Sr^(2+)(r=1.260Å)半径最为相近,因此更容易替代Sr^(2+)的格位,并且两种离子半径比Sr^(2+)小而使得样品晶体结构参数a,b,c和v逐渐减小。样品的最佳激发峰在403 nm处,相比于Ca_3Y_2(Si_3O_9)_2∶Sm^(3+)的激发峰出现了3 nm蓝移,表明样品在近紫外光下有较强的吸收,这种长紫外波长的光有利于在照明领域的应用。在403 nm近紫外光激发下,可以看出,在500～750 nm范围内, Sm^(3+)的发射峰位于564 nm(~4G_(5/2)→~6H_(5/2)), 601 nm(~4G_(5/2)→~6H_(7/2)), 648 nm(~4G_(5/2)→~6H_(9/2))和713 nm(~4G_(5/2)→~6H_(11/2)),其中601 nm发射峰强度最大,使样品呈现强烈的橙红色光。发射峰在607与618 nm处出现劈裂现象,是因为晶体场的相互作用引起了能级劈裂。单掺Sm^(3+)的发射光谱强度随着浓度的增加先增大后减小,当掺杂浓度为2%时发光强度最大。利用Blasse提出的能量传递临界距离公式,计算得出临界距离R_C≈19.734Å,从而说明了浓度猝灭原因是Sm^(3+)之间的多级相互作用。根据Dexter理论,计算出多极相互作用函数θ≈6,表明Sr_(2-x)Al_2SiO_7∶x%Sm^(3+)的浓度猝灭机理是电偶极-电偶极(d-d)相互作用。为进一步提高发光强度,掺杂了电荷补偿剂Li^+,使晶体内部电荷达到平衡。实验结果表明, Li^+最佳掺杂浓度为2%,与未加入电荷补偿剂相比,发光强度提高了2倍并测试其内量子效率为43.6%。荧光粉色坐标均在(0.60, 0.39)附近,位于橙红色区域,具有较高色纯度(约92.2%)。该荧光粉在三基色白光LED中的红色成分有应用潜力。
At present, aluminosilicates have attracted extensive attention because of their stable chemical properties and easy availability of raw materials, which have become an effective substrate for luminescent materials. Among them, barium aluminosilicate(Sr2Al2SiO7) belongs to the tetragonal system and has a stable crystal structure. As a commonly used activator, Sm3+ has characteristic peaks distributed in the band of 300~750 nm. Some characteristic excitation peaks are located in the near-ultraviolet region and have strong absorption in the near-ultraviolet region. Therefore, using Sr2Al2SiO7 as a matrix and Sm3+ as an activator, a red phosphor meeting the LED requirements can be prepared. In this work, a series of Sr2-x-yAl2SiO7∶x%Sm3+, y%Li+ phosphors were synthesized by high temperature solid phase method. The crystal structure, luminescence properties and internal quantum efficiency of the sample were characterized and measured by X-ray diffraction(XRD), photoluminescence spectroscopy(PL), and absolute quantum efficiency measurement system, and the XRD of the sample was refined and the color purity was calculated. The results show that the synthesized samples are all single-phase Sr2Al2SiO7, and do not cause phase transformation after doping with Sm3+ and charge compensator Li+. Relative to the other cations Sm3+(r=1.079 ?), Li+(r=0.920 ?) and the radius of Sr2+(r=1.260 ?) are the closest, so the two ions are more easily substituted for the Sr2+grid. The two ionic radius is smaller than Sr2+ to reduce the crystal structure parameters a, b, c and v of the sample. The best excitation peak of the sample is at 403 nm, which shows a blue shift of 3 nm compared to the excitation peak of Ca3Y2(Si3O9)2∶Sm3+, indicating that the sample has strong absorption under near-ultraviolet light. That is beneficial for applications in the field of lighting. Under the excitation of 403 nm near-ultraviolet light, it can be seen that the emission peak of Sm3+ ions is located at 564 nm(4G5/2→6H5/2) and 601 nm(4G5/2→6H7/2) in the range of 500~750 nm.), 648 nm(4G5/2→6H9/2) and 713 nm(4G5/2→6H11/2), of which the intensity of the 601 nm emission peak is the largest, which makes the sample appear strong orange red color. The emission peaks are cleaved at 607 and 618 nm because the interaction of the crystal fields causes energy level splitting. The intensity of the emission spectrum of the single-doped Sm3+ increases first and then decreases with the increase of the concentration, and reaches the strongest when the doping concentration is 2%. Using the energy transfer critical distance formula proposed by Blasse, the critical distance RC≈19.734 ? is calculated, which indicates that the concentration quenching is caused by the multi-level interaction between Sm3+ ions. According to the Dexter theory, the multipole interaction function θ≈6 is calculated, indicating that the concentration quenching mechanism of Sr2-xAl2SiO7∶x%Sm3+ is an electric dipole-electric dipole(d-d) interaction. In order to further increase the luminescence intensity, the charge compensator Li+ is doped to balance the internal charge of the crystal. The experimental results show that the optimum doping concentration of Li+ is 2%, and the luminescence intensity is increased by 2 times compared with the absence of charge compensator, and the internal quantum efficiency is tested to be 43.6%. Fluorescent pink coordinates are in the vicinity of(0.60, 0.39), located in the orange-red region, with a higher color purity(about 92.2%). The phosphor has potential applications in the red component of trichromatic white LEDs.
作者
王庆玲
迪拉热.哈力木拉提
沈玉玲
何久洋
艾尔肯.斯地克
WANG Qing-ling;Dilare Halimulati;SHEN Yu-ling;HE Jiu-yang;Aierken Sidike(Key Laboratory of Mineral Luminescent Material and Microstructure of Xinjiang, Xinjiang Normal University, Urumqi 830054, China)
出处
《光谱学与光谱分析》
SCIE
EI
CAS
CSCD
北大核心
2019年第4期1013-1017,共5页
Spectroscopy and Spectral Analysis
基金
国家自然科学基金项目(11464045)
新疆师范大学教育厅重点实验室招标课题(KWFG1704)资助
