【作者】 王志；

【导师】 李旭；

【作者基本信息】 河北大学 ， 物理电子学， 2022， 硕士

【摘要】 随着无机荧光粉的发展,在发光领域建立了一个新的里程碑。稀土激活的荧光粉是非常高效的材料,因为它们具有迷人的光电、生化和热特性以及生态友好性。其中硅酸盐作为基质具有优异的物理化学稳定性及热稳定性,并且其成本较低,适合制备性能优异的荧光粉,因此稀土掺杂的硅酸盐荧光粉被广泛研究。本文以具有氧化磷灰石结构的复杂硅酸盐Ba₄La₆O（Si O₄）₆为研究基质,掺杂的稀土离子包括Eu²⁺,Eu³⁺,Ce³⁺,Dy³⁺,采用了单一稀土离子掺杂和双离子共掺杂的方式,运用阳离子替换的策略调控基质,通过高温固相法成功制备出了Ba₄La₆O（Si O₄）₆:Eu²⁺,（Ba,Sr）₄La₆O（Si O₄）₆:Eu²⁺/Eu³⁺,Ba₄La₆O（Si O₄）₆:Ce³⁺,（Ba,Sr）₄La₆O（Si O₄）₆:Dy³⁺,Ba₄La₆O（Si O₄）₆:Ce³⁺/Dy³⁺,等一系列荧光粉材料,并且探索了分别在不同领域的应用。（1）Ba₄La₆O（SiO₄）₆:Eu²⁺硅酸盐荧光粉及其在光学测温领域的应用采用高温固相法制备了的具有氧化磷灰石结构的双格位取代的下转换复杂硅酸盐荧光粉Ba₄La₆O（Si O₄）₆:Eu²⁺,其中以Eu²⁺离子为发光中心。我们研究了其晶体结构,并且对XRD进行了结构精修,判断Eu²⁺离子取代了Ba²⁺离子格位。在荧光粉中,两个Ba²⁺格位可以被Eu²⁺离子占据,提供两种不同的配位环境,从而产生由Eu²⁺离子自旋允许的4f⁶5d→4f⁷电偶极跃迁引起的450-650 nm范围内的宽发射带,和归因于Eu²⁺从4f⁷到4f⁶5d¹跃迁的250-500 nm范围内的超宽激发带。通过测量Ba₄La₆O（Si O₄）₆荧光粉中的光致发光光谱和衰减曲线来验证两个不同的Eu²⁺发射中心的存在。探索了Eu²⁺离子的最佳掺杂浓度,以及稀土离子掺杂浓度和环境温度的改变对荧光粉的发光的影响。系统研究了Eu²⁺在293-453 K范围内的温度依赖性。基于寿命变化,研究了其在光学测温领域的应用,在460 K时得到最大相对灵敏度1.39%K^-1。（2）（Ba,Sr）₄La₆O（SiO₄）₆:Eu²⁺/Eu³⁺荧光粉及其LED和防伪领域的应用由于Ba₄La₆O（SiO₄）₆:Eu²⁺荧光粉热稳定性较差,我们决定以阳离子替换的策略调控基质,通过用Sr²⁺替换Ba²⁺来提高荧光粉的发光性能。实验采用高温固相法制备了硅酸盐荧光粉（Ba,Sr）₄La₆O（Si O₄）₆:Eu²⁺/Eu³⁺,其中以Eu²⁺/Eu³⁺离子为发光中心。Sr²⁺离子替换Ba²⁺离子可以调节晶体场环境,随着替换比例增加,一直到得到荧光粉Ba_1.42Sr_2.5La₆O（Si O₄）₆:0.08Eu,发光强度提高了2.07倍,T₅₀从380 K提高到453 K,达到了绿色荧光粉的一般商用标准。因此,将所制备的Ba_1.42Sr_2.5La₆O（Si O₄）₆:0.08Eu荧光粉、商用蓝色和红色荧光粉以及385 nm LED芯片集成在一起,制成了白光LED灯,实现了显色指数Ra=94.6的白光发射。除此之外,由于Sr²⁺离子掺杂,发现部分Eu³⁺离子不能被还原而保持在三价状态,在290 nm的激发光下发出明显的Eu³⁺离子的特征发射,且随着Sr²⁺离子替换比例增加而一直增强,即Ba_0.42Sr_3.5La₆O（Si O₄）₆荧光粉尤为显著。此外,仅对于Ba_0.42Sr_3.5La₆O（Si O₄）₆荧光粉,在250到360和480 nm的激发波长范围内,出现了发光颜色的波长依赖,荧光粉的发射可以从黄色变为绿色和黄色,这证明该荧光粉是一种很有前景的防伪候选材料。也证明阳离子替换策略是调控荧光粉发光的十分有意义、有前途的一种方法。（3）单相白光荧光粉Ba₄La₆O（SiO₄）₆:Dy³⁺调控的两种策略实验采用高温固相法制备出了Ba₄La₆O（Si O₄）₆:Dy³⁺荧光粉,Dy³⁺离子为发光中心。Ba₄La₆O（Si O₄）₆:Dy³⁺的激发光谱中有一系列分别位于297、324、349和385 nm处的尖峰,可归因于⁶H_15/2→⁴F_3/2,⁶H_15/2→⁴M_17/2,⁶H_15/2→⁶P_5/2和⁶H_15/2→4I_13/2 Dy³⁺的跃迁。在349 nm激发下,荧光粉在465-500 nm(⁴F_9/2→⁶H_15/2)和552-602 nm(⁴F_5/2→⁶H_13/2)范围内显示出Dy³⁺的特征蓝色和黄色发射,二者混合发出一种黄白光。为了调控发光颜色,我们采取了两种策略。首先是阳离子取代法,分别用Ba,Sr,Ca,Ge取代Ba和Si的位置,调控晶体场环境,进而调控位于480 nm和573 nm两个峰的发射峰比例,其中通过Sr取代Ba的策略效果最佳,使得发光强度增加,且I_480nm/I_573nm二者比例变化最大,随之研究了Sr²⁺离子引入的最佳含量。第二种采用共掺杂的方式,通过在Ba₄La₆O（Si O₄）₆:Dy³⁺荧光粉中共掺杂Ce³⁺离子,填补蓝光,使得样品发出合适的白光。这也为单相白光的实现提供了一种有效思路。更多还原

【Abstract】 With the development of inorganic phosphors,a new milestone has been established in the field of luminescence.Rare earth-activated phosphors are very efficient materials because of their fascinating optoelectronic,biochemical and thermal properties as well as eco-friendliness.Among them,silicate as a matrix has excellent physical and chemical stability and thermal stability,and its cost is low,which is suitable for the preparation of phosphors with excellent performance.Therefore,rare earth-doped silicate phosphors have been widely studied.In this paper,the complex silicate Ba₄La₆O（Si O₄）₆ with oxidized apatite structure is used as the research matrix,and the doped rare earth ions include Eu²⁺,Eu³⁺,Ce³⁺,Dy³⁺,using single rare earth ion doping and double ion co-doping In this way,Ba₄La₆O（Si O₄）₆:Eu²⁺,（Ba,Sr）₄La₆O（Si O₄）₆:Eu²⁺/Eu³⁺,Ba₄La₆O（Si O₄）₆:Ce³⁺,（Ba,Sr）₄La₆O（Si O₄）₆:Eu²⁺/Eu³⁺,Ba₄La₆O（Si O₄）₆:Ce³⁺,（Ba,Sr）₄La₆O（Si O₄）₆:Dy³⁺,Ba₄La₆O（Si O₄）₆:Ce³⁺/Dy³⁺,and a series of phosphor materials,and their applications in different fields were explored.（1）Ba₄La₆O（Si O₄）₆:Eu²⁺silicate phosphor and its application in the field of optical temperature measurementThe double-site substituted down-conversion complex silicate phosphor Ba₄La₆O（Si O₄）₆:Eu²⁺with oxidized apatite structure was prepared by high temperature solid-phase method,in which Eu²⁺ion is the luminescent center.We studied its crystal structure and refined the XRD structure,and judged that the Eu²⁺ion replaced the Ba²⁺ion site.In phosphors,two Ba²⁺sites can be occupied by Eu²⁺ions,providing two different coordination environments,resulting in a 4f⁶5d→4f⁷ electric dipole transition in the range of 450-650 nm induced by the Eu²⁺ion spin-allowed 4f⁶5d→4f⁷ electric dipole transition.Broad emission band,and an ultrabroad excitation band in the 250-500 nm range attributed to the transition of Eu²⁺from 4f⁷ to 4f⁶5d¹.The existence of two distinct Eu²⁺emission centers was verified by measuring the photoluminescence spectra and decay curves of Ba₄La₆O（Si O₄）₆ phosphors.The optimal doping concentration of Eu²⁺ions and the effects of the doping concentration of rare earth ions and ambient temperature on the luminescence of phosphors were explored.The temperature dependence of Eu²⁺in the range of 293-453 K was systematically studied.Based on the lifetime change,its application in the field of optical temperature measurement was studied,and the maximum relative sensitivity of 1.39%K^-1 was obtained at 460K.（2）（Ba,Sr）₄La₆O（Si O₄）₆:Eu²⁺/Eu³⁺phosphors and their applications in LED and anti-counterfeiting fields.Due to the poor thermal stability of Ba₄La₆O（Si O₄）₆:Eu²⁺phosphors,we decided to use a cation replacement strategy to control the matrix,and improve the luminescence performance of the phosphors by replacing Ba²⁺with Sr²⁺.The silicate phosphors（Ba,Sr）₄La₆O（Si O₄）₆:Eu²⁺/Eu³⁺were prepared by high temperature solid-phase method in the experiment,and Eu²⁺/Eu³⁺ions were used as luminescent centers.The replacement of Ba²⁺ions by Sr²⁺ions can adjust the crystal field environment.As the replacement ratio increases,until the phosphor Ba_1.42Sr_2.5La₆O（Si O₄）₆:0.08Eu is obtained,the luminous intensity is increased by 2.07 times,and the T50 is increased from 380 K to 453 K,reaching the general commercial standard of green phosphors.Therefore,the as-prepared Ba_1.42Sr_2.5La₆O（Si O₄）₆:0.08Eu phosphor,commercial blue and red phosphors,and 385 nm LED chips were integrated to make a white LED lamp with a color rendering index Ra=94.6 white light emission.In addition,due to the doping of Sr²⁺ions,it was found that some Eu³⁺ions could not be reduced and remained in the trivalent state,and the characteristic emission of Eu³⁺ions was obvious under the excitation light of 290 nm,and with the increase of the replacement ratio of Sr²⁺ions.It has been enhanced,that is,Ba_0.42Sr_3.5La₆O（Si O₄）₆ phosphor is particularly remarkable.Furthermore,only for the Ba_0.42Sr_3.5La₆O（Si O₄）₆ phosphor,a wavelength dependence of the emission color appears in the excitation wavelength range of 250 to 360 and 480 nm,the emission of the phosphor can change from yellow to green and yellow,which proves that the phosphor is a promising anti-counterfeiting candidate material.It is also proved that the cation replacement strategy is a very meaningful and promising method to control the luminescence of phosphors.（3）Two strategies for regulation of single-phase white phosphor Ba₄La₆O（Si O₄）₆:Dy³⁺.In the experiment,Ba₄La₆O（Si O₄）₆:Dy³⁺phosphor was prepared by high temperature solid-phase method,and Dy³⁺ion was the luminescent center.There are a series of sharp peaks at 297,324,349 and 385 nm in the excitation spectrum of Ba₄La₆O（Si O₄）₆:Dy³⁺,which can be attributed to ⁶H_15/2→⁴F_3/2,⁶H_15/2→⁴M_17/2,⁶H_15/2→⁶P_5/2 and ⁶H_15/2→⁴I_13/2 Transition of Dy³⁺.Under excitation at 349 nm,the phosphor exhibits characteristic blue and yellow emission of Dy³⁺in the range of 465-500 nm(⁴F_9/2→⁶H_15/2)and 552-602 nm(⁴F_5/2→⁶H_13/2),and they mixture emits a yellow-white light.To tune the emission color,we adopted two strategies.The first is the cation substitution method.The positions of Ba and Si are replaced with Ba,Sr,Ca,and Ge,respectively,to control the crystal field environment,and then control the ratio of the emission peaks located at 480 nm and 573 nm.The strategy of replacing Ba by Sr The effect was the best,which increased the luminous intensity,and the ratio of I_480nm/I_573nmchanged the most.Then,the optimum content of Sr²⁺ions was studied.The second method uses co-doping,by co-doping Ce³⁺ions in the Ba₄La₆O（Si O₄）₆:Dy³⁺phosphor to fill the blue light,so that the sample emits suitable white light.This also provides an effective idea for the realization of single-phase white light.更多还原