Al替代对β-Ga_2O_3∶Cr^(3+)结构与发光性能影响

Structure and Luminescence Properties of Ga_2O_3∶Cr^(3+) by Al Doping

高温固相法制备了(Ga1-x Alx)2O3∶Cr3+(x=0,0.1,0.2,0.3,0.4,0.5)系列荧光粉。X射线衍射分析表明Al 3+含量增加后,物相依然保持β-Ga2O3的相。此外随着Al离子含量的逐渐增加,高衍射角峰位向右移动表明Al离子进入了β-Ga2O3晶格中。激发光谱中258,300,410和550nm左右的峰位分别对应基质Ga2O3的带与带的吸收跃迁、电荷迁移带跃迁、Cr3+的4 A2→4 T1以及4 A2→4 T2跃迁。随着Al离子掺杂量的增加,激发光谱峰位都呈现出不同程度的蓝移现象,这分别是由于基质的带隙能量、Cr3+与配体之间的电负性以及晶场强度增大所导致的。在发射光谱中,随着Al 3+替代Ga3+,Cr3+的发光由宽带发射变为窄带发射,这是由于Al 3+的掺入改变了Cr3+周围的晶场,从而Cr3+的红光发射由原来的4 T2→4 A2变为2 E→4 A2跃迁发射。Al离子掺杂改善了样品的长余辉发光特性,并且Al离子含量达到0.5时显示出较长时间的肉眼可见的近红外余辉发射。热释发光曲线显示材料中具有合适的陷阱能级,这也是材料产生长余辉发光的原因。

The A1 doping gallate phosphor （Gal-~AI~）203 ： Cr3＋ （x=0, 0. 1, 0.2, 0.3, 0. 4, 0.5） was synthesized by a high temperature solid-state reaction method. The X-ray diffractions show that the phase of the phosphors remains to be Ga20s struc ture with increase in the contents of A13＋ ion. Beside, the fact that the X-ray diffraction peak shifts towards big angles with in creasing AP＋ ions content shows that A13＋ ions entered the Ga2 03 lattice. The peaks of the excitation spectra located at 258, 300, 410 and 550 nm are attributed to the band to band transition of the matrix, charge transfer band transition, and 4A2-~4T1 and 4Az→472 transition of Cr3＋ ions, respectively. Those excitation spectrum peak positions show different degrees of blue shift with the increase in the AP＋ ions content. The blue shift of the first two peaks are due to the band gap energy of substrate and the electronegativity between Cr3＋ ions and ligands increasing, respectively. The blue shift of the energy level transition of Cr3＋ ion is attributed to crystal field strength increasing. The Cr3＋ ion luminescence changes from a broadband emission to a narrow- band emission with AP＋ doping, because the emission of Cr3＋ ion changed from 4 T2→4A2 to 2E→4A2 transition with the crystal field change after A13＋ ions doping. The AP＋ ions doping improved the long afterglow luminescence properties of samples, and the sample showed a longer visible near infrared when AP＋ ions content reaches 0.5. The thermoluminescence curve shows the sample with suitable trap energy level, and this is also the cause of the long afterglow luminescence materials.