Single Crystalline Films of Ce3+-Doped Y3MgxSiyAl5−x−yO12 Garnets: Crystallization, Optical, and Photocurrent Properties

This study explores the growth of Liquid Phase Epitaxy (LPE) and investigates the optical and photovoltaic properties of single crystalline film (SCF) phosphors. These phosphors are based on Ce3+-doped Y3MgxSiyAl5−x−yO12 garnets, with varying Mg and Si concentrations ranging from x = 0 to 0.345 and y = 0 to 0.31. The properties analyzed include absorbance, luminescence, scintillation, and photocurrent in comparison with their Y3Al5O12:Ce (YAG:Ce) counterparts. Specially prepared low-concentration (x, y < 0.1) YAG:Ce SCFs, which included Mg2+ and Mg2+–Si4+ codopants, demonstrated increased photocurrents with rising dopant levels. These SCFs consistently exhibited Mg2+ excess in their as-grown state. When exposed to α-particles, these garnets displayed a low light yield (LY) and a rapid scintillation response with nanosecond decay times, attributed to the production of Ce4+ ions compensating for the Mg2+ excess. Post-annealing at temperatures above 1000 °C in a reducing atmosphere (95%N2 + 5%H2) converted Ce4+ back to Ce3+, leading to an LY of about 42% and decay kinetics similar to those of YAG:Ce SCFs. Photoluminescence studies revealed the formation of Ce3+ multicenters and energy transfer among them, influenced by variable crystal field strengths at nonequivalent dodecahedral sites, due to Mg2+ and Si4+ substitution at octahedral and tetrahedral positions, respectively. Compared to YAG:Ce SCFs, the luminescence spectra of Y3MgxSiyAl5−x−yO12:Ce SCFs expanded significantly in the red region. Leveraging these advantageous alterations in optical and photocurrent properties through Mg2+ and Si4+ alloying, a new generation of SCF converters could be developed for applications in white LEDs, photovoltaics, and scintillators.

本研究围绕液相外延（Liquid Phase Epitaxy，LPE）生长工艺展开探索，并对掺Ce³+的Y3MgxSiyAl5−x−yO12石榴石基单晶薄膜（single crystalline film，SCF）荧光粉的光学与光伏特性开展研究。其中Mg与Si的掺杂浓度范围分别为x=0至0.345、y=0至0.31。本次分析的特性包括吸光度、发光性能、闪烁性能及光电流，并与钇铝石榴石掺铈（Y3Al5O12:Ce，YAG:Ce）单晶薄膜样品进行对照。
专门制备的低浓度（x、y < 0.1）共掺Mg²+及Mg²+–Si⁴+的YAG:Ce单晶薄膜，其光电流随掺杂浓度升高而显著提升。这类单晶薄膜在生长态下普遍存在Mg²+过量的情况。当受α粒子辐照时，该类石榴石材料表现出较低的光产额（light yield，LY）与纳秒级快速闪烁衰减响应，这一现象归因于Ce⁴+离子的生成以补偿Mg²+过量带来的电荷失衡。
在95%N2 + 5%H2的还原性气氛中、1000℃以上温度进行后退火处理，可将Ce⁴+还原为Ce³+，使材料光产额恢复至约42%，且衰减动力学特性与YAG:Ce单晶薄膜基本一致。光致发光研究表明，由于Mg²+与Si⁴+分别取代八面体与四面体格位的Al³+，十二面体不等价格位处的晶体场强度发生变化，进而诱导Ce³+多中心形成并产生相互间的能量转移。
与YAG:Ce单晶薄膜相比，Y3MgxSiyAl5−x−yO12:Ce单晶薄膜的发光光谱在红光区域发生显著展宽。通过利用Mg²+与Si⁴+合金化带来的光学与光电流特性优化，可开发新一代单晶薄膜转换器，应用于白光LED、光伏器件及闪烁体等领域。