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LaB_6 optical properties of first-principles calculations and experimental study

Author: XiaoLiHua
Tutor: FuYunChang
School: Kunming University of Science and Technology
Course: Optics
Keywords: Lanthanum hexaboride LaB6 First Principles Electronic structure Optical Properties Transmission characteristics
CLC: O482.3
Type: Master's thesis
Year: 2010
Downloads: 117
Quote: 0
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Abstract


LaB6 thermionic emission cathode material not only has good thermal conductivity and electrical conductivity properties such as metal, and has a high melting point, high hardness and high chemical stability, ceramics, it has excellent properties such broad application prospect. Researchers recently found to have free electrons localized surface plasmon resonance (LSPR) effects of lanthanum hexaboride (LaB6) nanopowders in the sunlight has a significant near-infrared radiation absorption and scattering, which is considered to be a new type of windows with energy-saving insulation materials, making it become the ATO, ITO photovoltaic research field after another hot research topic. In this paper, the theory of first-principles density functional theory based ab initio molecular dynamics method to systematically calculate LaB6 ground state electronic structure and optical properties of the density of states as well as temperature, external pressure LaB6 electron structure and other properties were research; addition, experiments on the use of microwave solid-phase synthesis method at low temperature synthesis of lanthanum hexaboride (LaB6) nanopowders prepared PVB LaB6 nano-powder coating, its optical properties and thermal effects are discussed. Its main contents are as follows: 1. Theoretical calculation results show that: ①. LaB6 using density functional theory calculations of the electronic structure and optical properties of the density of states. LaB6 band structure analysis shows that a conductor, the valence band of the B 2p state electron conduction band mainly by the composition of La 5d6s state electron; static dielectric constant ε1 (0) = 213.7, the refractive index n (0 ) = 14.803, the absorption coefficient in the visible range of the minimum trough 21585.2cm-1. ②. Theoretical transmittance in the ultraviolet and near infrared almost zero in the case, LaB6 has a high visible light transmittance, was \theoretical maximum transmission rate, 57.6%. The results for the LaB6 design and application of optical materials provide a theoretical basis. ③. Calculated under external pressure modulation LaB6 electronic structure and optical properties, the results showed that: when the external pressure increases to a certain extent, the optical properties of LaB6 mutation will occur. ④. LaB6 and CaB6 essential difference depends on the optical properties of the electronic structure of La 5d and Ca 3d contribution of its own material. 2 Experimental results show that: the coating prepared LaB6/PVB transparent insulation coating. In LaB6 content of 0.05% in the visible region (380-780 nm) transmission rate of up to 79%, while the near infrared region (780-1000 nm) of the shield was 54%. The results illustrate the PVB containing nano LaB6 coating on near-infrared light with a clear barrier effect. 60min after irradiation under an infrared lamp, transparent insulation glass cabinet temperature between the glass cabinet with blank temperature up to 2.5 ℃, thermal insulation effect is remarkable.

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CLC: > Mathematical sciences and chemical > Physics > Solid State Physics > Solid nature of the > Optical Properties
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