Cosolvent-Free Sol–Gel Synthesis and Optical Characterization of Silica Glasses Containing LaF<sub>3</sub> and (La,Er)F<sub>3</sub> Nanocrystals
作者:Kotomi Suzuki、Koichi Kajihara、Kiyoshi Kanamura
DOI:10.1246/bcsj.20140088
日期:2014.7.15
Monolithic transparent silica glasses containing LaF3 nanocrystals were prepared by a cosolvent-free sol–gel method based on the pyrolysis of lanthanum trifluoroacetate. The two-step mixing of alkoxide and water, consisting of partial hydrolysis under acidic conditions and subsequent neutralization to catalyze the polycondensation of hydrophobic silica oligomers, makes it possible to shorten the processing time while eliminating the need for cosolvents. The size of the LaF3 nanocrystals decreases with an increase in the volume fraction of LaF3. This suppresses Rayleigh scattering and improves transparency at LaF3-rich compositions. Green and red upconversion photoluminescence (PL) bands, mainly caused by energy-transfer upconversion (ETU), are observed in Er-doped samples under excitation at 980 nm. The PL intensity drastically increases with an increase in the volume fraction of the LaF3 phase as a result of improved crystallinity of LaF3. The quantum yields recorded for the green and red upconversion PL bands were ca. 0.08% and ca. 0.04%, respectively.
通过一种基于三氟乙酸镧热解的无助溶剂溶胶-凝胶法,制备出了含有 LaF3 纳米晶体的单片透明二氧化硅玻璃。烷氧基化合物和水的两步混合法包括在酸性条件下进行部分水解,然后进行中和以催化疏水性二氧化硅低聚物的缩聚,因此可以缩短加工时间,同时无需助溶剂。LaF3 纳米晶体的尺寸随着 LaF3 体积分数的增加而减小。这抑制了瑞利散射,提高了富含 LaF3 成分的透明度。在 980 纳米波长的激发下,在掺 Er 的样品中观察到了主要由能量转移上转换(ETU)引起的绿色和红色上转换光致发光(PL)带。由于 LaF3 的结晶度提高,随着 LaF3 相体积分数的增加,PL 强度也急剧增加。绿色和红色上转换 PL 波段的量子产率分别约为 0.08% 和 0.0%。分别约为 0.08% 和 0.04%。