稀土硼化物LaxCe1-xB6亚微米粉的制备及光吸收研究

Synthesis and optical absorption properties of La_xCe_(1-x)B_6 submicron powders

以稀土氧化物La2O3和CeO2为稀土源,以NaBH4为硼源在真空环境中通过固相反应成功制备出了分散性好的单相三元LaxCe1xB6亚微米粉.系统研究了掺杂元素La对CeB6物相,微观结构及光吸收性能的影响.实验结果表明,La元素的掺杂没有改变CeB6的物相和晶体结构,而是无序替代了Ce原子晶位.光吸收结果表明,随着La掺杂量的增加LaxCe1xB6分散液吸收谷波长从620 nm减小到610 nm出现了蓝移现象.

According to original knowledge, lanthanum hexaboride （LAB6） as an excellent thermionic electron emitter is char- acterized by a low work function, a high emission density, and a high brightness. Recently, much attention has been drawn to its another excellent optical properties： strong light absorption in near infrared rays （NIR）, and transparency in visible light （VL）, which result from the free electron plasmon resonance. However, up to now the optical properties and syntheses of ternary rare-earth hexaborides have been very rarely reported in the literature. In this paper, ternary LaxCel-xB6 submicron crystallines are successfully synthesized using a solid-state reaction, in which La203 and CeO2 are used as rare-earth sources and NaBH4 as boron sources in a continuous vacuum condition. Effects of La doping content on the LaxCel-xB6 phase composition, microstructure, and optical absorption properties are investigated by X-ray diffraction, scanning electron microscope （SEM）, and transmission electron microscope （TEM）. It is found that all the synthesized samples are composed of CaB6-type single-phase alloy with a space group Pm3m at the reaction temperature of 1200 ℃ held by 2 h. The SEM results indicate that the cubic-shaped ternary LaxCel-xB6crystals with a mean size of 200 nm are obtained and the energy dispersive spectrometer results confirm that the La atoms are randomly distributed at the lattice sites of CeB6. High resolution transmission electron microscope images reveal the single-crystalline nature; and the FFT pattern indicates the lattice fringe d = 0.42 nm which agrees well with the （100） crystal plane. EDS analysis of TEM also indicates the La element has been doped into CeB6. And the optical absorption result shows that the absorption valley of CeB6 is 62 nm. With increasing La doping content to x = 0.6 and 0.8, the absorption valleys of La0.6Ce0.4B6 and La0.8Ce0.2B6 decrease to 613 and 610 nm respectively indicating the blueshifts of the wavelength of absorption valley From the view point of practical application, the tunable characteristic of LaxCel-xB6 may extend the optical applications in improving the efficiency of organic photovoltaics, replacing the expensive gold and silver nanoparticles, which may have a good usage in optical filters.