镓置换铝对SrAl2Si2O8∶Eu2+晶体结构和发光特性的影响

采用高温固相法在弱还原气氛下制备了Sr0.955Al2－xGaxSi2O8∶Eu2+ (x=0～1.0)系列荧光粉,研究了Ga3+置换铝Al3+对晶体结构和光谱特性的影响.Ga3+进入SrAl2Si2O8晶格与Al3+发生类质同相替代使晶胞参量a、b、c、β和晶胞体积V都随Ga3+置换量呈线性增大,表明形成了连续固溶体.镓置换铝对晶胞参量c的影响最明显,b其次,a最小.Eu2+的宽带激发光谱位于230～400 nm,表观峰值位于350 nm,可由267 nm、305 nm、350 nm和375 nm四个峰拟合而成.随着镓置换量增加,较短波长的三个激发峰发生红移并且267 nm和350 nm峰强度减弱,305 nm峰强度明显增强,375 nm峰位和强度基本不变,表观激发峰半高宽由109 nm减小至98 nm,基本不随镓置换量变化.发射光谱位于380～600 nm为不对称宽带,可由406 nm和441 nm两峰拟合而成并且随Ga3+置换量增加线性红移,拟合发射光谱峰面积之比线性递增,Ga3+进入晶格对较长波长发射中心影响较大.Ga3+置换量为1.0 mol时,表观发射峰位从407 nm线性红移至422 nm,表观峰值随Ga3+置换量线性增大,半高宽由58 nm增加至79 nm.镓置换铝造成Eu-O距离变小,发光中心Eu2+所处晶体场增强,5d轨道能级分裂变大,最低发射能级下移.

Effect of Substituting Ga for Al on Structure and Spectral Properties of Phosphors SrAl2Si2O8∶Eu2+

 A series of phosphors Sr0.955Al2－xGaxSi2O8∶Eu2+ (x=0～1.0) was prepared via solid-state reaction in weak reductive atmosphere.Lattice positions and the luminescent mechanism of Eu2+ in the host were discussed,and effects of Ga3+-substitution on the host lattice and spectral properties were investigated.The results showed that complete solid solutions formed in the whole range of x=0～1.0 while Ga3+ entered SrAl2Si2O8 lattice and substituted Al3+.The lattice parameters (a,b,c) and unit cell volume of phosphors Sr0.955Al2－xGaxSi2O8∶Eu2+ (x=0～1.0) increased linearly as Ga3+ content increased in the phosphors.When Ga3+ substituted for Al3+,the most obvious changes happened in cell parameter c,b was the second and a was the minimum.A broad excitation spectrum of Eu2+ presented from 230 nm to 400nm and peaked at 350 nm,which consists of 267 nm,305 nm,350 nm and 375 nm excitation bands.The three shorter wavelengths excitation peaks were shifted to red and the peak intensities of 267 nm and 350 nm were decreased.The peak intensity of 305 nm increased significantly while the peak position and intensity of 375 nm unchanged basically as the increased substitution of Ga3+.The FWHM of the apparent excitation peak narrowed from 109 nm to 98 nm.The broad and asymmetric emission spectrum among 380 nm and 600 nm and apparent peak was at 407 nm,which could be fitted by two peaks at 406 nm and 441 nm.The two fitted peaks were red shifted and the intensity ratio of the fitted peaks increased linearly with the increasing of the amount of Ga3+-substitution.The apparent emission peak was red shift from 407 nm to 422 nm and FWHM increased from 58 nm to 79 nm while Ga3+ content was up to 1.0 mol.The distance of Eu-O was shorted due to Al3+ is replaced by Ga3+.The crystal field of the emitting center Eu2+ location was enhanced.The splitting of 5d orbital levels was increased and the lowest emission level was expanded to lower.