(Mg1-x-yBaxSry)1.95SiO4∶0.05Eu荧光粉的光谱研究及紫外激发色像图建立

采用高温固相法制备了新型(Mg1-x-yBaxSry)1.95SiO4∶0.05Eu荧光粉,其中包括3个二元碱土离子配比系列和3个代表性三元碱土离子配比系列(Ba不变而Mg/Sr比连续变化、Mg/Sr比不变而Ba含量连续变化)共计6个系列,并研究其光谱性能(激发谱和发射谱)、紫外(254和365 nm)发光照相记录及CIE值对应色像。借鉴三元相图的建立思路,由这些二元和代表性三元数据推导三元色像图,用于新型荧光粉的系统开发。所制备的荧光粉系列包括:Mg2SiO4-Sr2SiO4,Ba2SiO4-Sr2SiO4,Mg2SiO4-Ba2SiO4,Ba原子比含量为0.2(Mg/Sr原子比连续变化),Ba原子比含量为0.6(Mg/Sr原子比连续变化),Mg/Sr原子比为1/4(Ba原子比含量连续变化系列)。其对应的254 nm激发下光谱性能、发光照相记录、和CIE色像分析表明:Eu离子可以三价和二价形式存在于(Mg1-x-yBaxSry)2SiO4中;二元系列中(Mg1-xBax)2SiO4和(Ba1-ySry)2SiO4基体中随着Ba原子比的增加荧光粉逐渐由红(对应Eu3+5D0→7F1和5D0→7F2电子跃迁窄带发射)变绿(对应Eu2+4fn-15d→4fn电子跃迁发射宽带发射)且前者变化的更快;二元系列中(Mg1-ySry)2SiO4系列为红色荧光粉,且随着Sr含量增加红色发光增大;三元系列中(Bax(Mg0.2Sr0.8)1-x)2SiO4(Mg/Sr=1/4)随着Ba离子量增加荧光粉也逐渐由红变绿,其变化速度介于Mg/Sr比等于0(即Ba2SiO4-Sr2SiO4系列)和Mg/Sr比等于∝(即Ba2SiO4-Mg2SiO4系列);三元系列中(Ba0.2SryMg0.8-y)1.95SiO4为红色荧光粉,而(Ba0.6SryMg0.4-y)2SiO4随着Mg/Sr原子比增加逐渐由红转蓝绿光。365 nm激发下荧光发射的变化规律与254 nm激发下大体一致,但是同一样品在365 nm激发下其绿光波段发射要比254 nm激发要强且其红光波段发射要比254nm激发要弱,故(Mg1-xBax)2SiO4,(Ba1-ySry)2SiO4,(Bax(Mg0.2Sr0.8)1-x)2中对应的由红变绿时Ba含量分别为40at%,60at%,60at%(254 nm激发下60at%,80at%,70at%)且(Ba0.6SryMg0.4-y)2SiO4中由红变绿的Mg/Sr比为1/4(254 nm激发下为2/3)。据此建立Eu掺杂Ba2SiO4-Mg2SiO4-Sr2SiO4紫外激发色像图。借由色像图可知(Mg1-x-yBaxSry)1.95SiO4∶0.05Eu荧光粉紫外激发下发射光变化规律,即基体组分靠近Ba2SiO4端发射绿色而靠近Mg2SiO4或Sr2SiO4端发射红色,Mg/Sr比越大随着Ba原子的增加荧光粉的由红转绿的速度越快;同一样品在365 nm激发下其绿光波段发射要比254 nm激发要强且其红光波段发射要比254 nm激发要弱,(Mg1-x-yBaxSry)1.95SiO4∶0.05Eu荧光粉中当Ba>80at%,Mg>90at%(或Sr>80at%)荧光粉可分别用作高效绿色、红色荧光粉;此外,当组分为(Mg0.8Sr0.2)1.95SiO4∶0.05Eu,(Ba0.8Mg0.16Sr0.04)1.95SiO4∶0.05Eu是紫外激发下(254和365 nm)最好的红色和绿色荧光粉。

Photoluminscence Spectra and Ternary CIE Colour Image of (Mg1-x-yBaxSry)1.95SiO4∶0.05Eu Phosphor Series

A novel(Mg1-x-yBaxSry)1.95SiO4∶0.05 Eu phosphor was prepared by high-temperature solid state reaction method,including 3 binary alkaline earth ion ratio series and 3 representative ternary alkaline earth ion ratio series(Ba is constant and the Mg/Sr ratio is continuously changed,the Mg/Sr ratio is constant and the Ba content is continuously changed.).As for the 6 series,the spectral properties(excitation and emission spectra),ultraviolet(254 and 365 nm)luminescence recordings and CIE values corresponding to the color images were studied in detail.Like the way to establish a ternary phase diagram,a ternary colour image is derived from these binary and representative ternary data.It can be used to study and screen a new phosphor series in a more efficient way.The prepared phosphor series include:Mg2SiO4-Sr2SiO4,Ba2SiO4-Sr2SiO4,Mg2SiO4-Ba2SiO4,Ba atomic ratio of 0.2(Mg/Sr atomic ratio continuously changed),Ba atomic ratio of 0.6(Mg/Sr atomic ratio continuously changes),the atomic ratio of Mg/Sr is 1/4(the series of continuous changes in Ba atomic content).Its corresponding spectral performance,luminescence recording,and CIE chromatic analysis at 254 nm excitation indicate that:Eu ions exist trivalent and divalent in(Mg1-x-yBaxSry)2SiO4;for the binary series(as the matrix as(Mg1-xBax)2SiO4 or(Ba1-ySry)2SiO4),with the increase of Ba atomic ratio,the phosphor gradually turns red(corresponding to Eu3+ions 5D0→7F1 and 5D0→7F2 electron transition narrow band emission)to green(corresponding to Eu2+ion 4fn-15d→4fn electronic transition emission broadband emission),and the former series change faster;the binary series as(Mg1-ySry)2SiO4 were red phosphors,and the red luminescence increases with the increase of Sr content.For the ternary series(Bax(Mg0.2Sr0.8)1-x)2SiO4(Mg/Sr=1/4),as Ba ion amount increases,the phosphor gradually changes from red to green,and the rate of change is determined by the ratio of Mg/Sr equal to 0(ie Ba2SiO4-Sr2SiO4 series)and the ratio of Mg/Sr is equal to∝(ie Ba2SiO4-Mg2SiO4 series);the ternary series(Ba0.2SryMg0.8-y)1.95SiO4 are also red phosphors,and(Ba0.6SryMg0.4-y)2SiO4 gradually turn blue and green with the atomic ratio of Mg/Sr increasing.The evolution of fluorescence emission at 365 nm excitation is generally consistent with that at 254 nm excitation,but the emission of green light in the same sample at 365 nm is stronger than that at 254 nm and the emission in the red band is weaker than that at 254 nm.Therefore,the contents of Ba in(Mg1-xBax)2SiO4,(Ba1-ySry)2SiO4,(Bax(Mg0.2Sr0.8)1-x)2 from red to green are 40 at%,60 at%,60 at%,respectively(60 at%,80 at%,70 at%at 254 nm excitation),and Mg/Sr ratio from red to green in(Ba0.6SryMg0.4-y)2SiO4 is 1/4(2/3 at 254 nm excitation).Based on this,ternary CIE colour image of Eu-doped Ba2SiO4-Mg2SiO4-Sr2SiO4 is established.It can be seen from the spectral image that the(Mg1-x-yBaxSry)1.95SiO4∶0.05 Eu phosphor emits light under UV excitation,that is,the matrix component emits green near the Ba2SiO4 corner and emits red near the Mg2SiO4 or Sr2SiO4 corner.The larger the Mg/Sr ratio is,the faster the phosphor turns from red to green as the Ba atom increases.The green light emission of the same sample is stronger than the 254 nm excitation at 365 nm excitation and the red emission is weaker than the 254 nm excitation.(Mg1-x-yBaxSry)1.95SiO4∶0.05 Eu phosphor is Ba>80 at%,and Mg>90 at%(or Sr>80 at%)phosphor can be used as high-efficiency green and red fluorescence,respectively;when the composition is(Mg0.8Sr0.2)1.95SiO4∶0.05 Eu,(Ba0.8Mg0.16Sr0.04)1.95SiO4∶0.05 Eu is the best red and green phosphor for UV excitation.