白光LED用Ca_(0.955)Al_2Si_(2-x)Ti_xO_8:Eu^(2+)荧光粉的晶体结构和光谱特性研究

Crystal Structure and Luminescent Properties of Ca_(0.955)Al_2Si_(2-x)Ti_xO_8:Eu^(2+) Phosphors for White LED

通过高温固相法在弱还原气氛下合成Ca0.955Al2Si2-xTixO8∶Eu2+(x=0～1.0)系列试样荧光粉,系统研究了Ti4+置换Si4+对其晶体结构和光谱特性的影响。Ti4+以类质同相替代CaAl2Si2O8晶格中的Si4+形成连续固溶体,随着Ti4+置换量的增加,晶胞参数a,b,c,γ和晶胞体积V都呈线性递增,晶面夹角α和β均呈线性递减。Ti4+置换Si4+对晶胞参数c的影响最显著,b其次,a最小。荧光激发谱为宽带,位于225～400 nm,可由280,322,353和382 nm 4个峰拟合而成,表观峰值位于351 nm;随着Ti4+置换量的增加,半高宽从115 nm减小到91 nm。发射光谱位于375～600 nm,表观峰值位于426 nm,可由428和458 nm两峰拟合而成并且随Ti4+置换量增加线性红移,Ti4+进入晶格对较长波长发射中心影响较大;Ti4+置换量为1.0 mol时,表观发射峰位从426 nm线性红移至430 nm,半高宽由66 nm增加至80 nm。随着Ti4+置换量Si4+进入基质晶格,造成Eu-O距离变小,使得Eu2+所处的晶体场强度增强,发光中心Eu2+的5d能级分裂增大,造成Eu2+最低发射能级重心下移,两拟合谱峰峰位均呈线性红移。

A series of phosphors C%.95sAL2Si2_xTi,Os： Eu2＋ （x = 0 - 1.0） were prepared via solid-state reaction in weak reductive atmosphere. The lattice positions and the luminescent mechanism of Eu2＋ in the host were discussed; the effects of Ti4 ~ -substitution on the host lattice and spectral properties were also investigated. The results showed that complete solid solutions formed in the whole range of x = 0 ~ 1.0 while Ti4 ~ entered CaA12 Si20s lattice and substituted Si4 ＋. The lattice parameters （ a, b, c, T） and unit cell vol- ume （V） of phosphors Cao. 95s A12 Si2 _, Ti~ Os ： Eu2 ＋ （ x = 0 ~ 1.0 ） increased linearly and the lattice parameters （ ct, fl ） decreased linearly as Ti4＋ content increased in the phosphors. When Ti4＋ substituted for Si4＋ , the most obvious change was in ceil parameters c, b sec- ond, a minimum. A broad excitation spectrum of Eu2＋ presented from 225 to 420 nm and peaked at 351 nm, which consisted of 280, 322, 353 and 382 nm excitation bands. The FWHM of the apparent excitation peak narrowed from 115 to 91 nm. The broad and asym- metric emission spectrum among 375 and 600 nm and apparent peak was at 426 nm, which could be fitted by two peaks at 422 and 458 nm. The two fitted peaks were red shifted with the increase of the amount of Ti4＋ -substitution. The apparent emission peak was red shift from 426 to 430 nm and FWHM increased from 66 to 80 nm while Ti4＋ content was up to 1.0 mol. The distance of Eu and O be- came short due to Si4＋ was replaced by Ti4＋. The crystal field of the emitting center Eu2＋ location was enhanced. The splitting of 5d or- bital levels was increased and the lowest emission level was expanded to lower, the two fitted peaks were red shifted.