A series of SiO_2/β-Zn_4Sb_3 core-shell composite particles with 3,6,9,and 12 nm of SiO_2 shell in thickness were prepared by coatingβ-Zn_4Sb_3 microparticles with SiO_2 nanoparticles formed by hydrolyzing the tetraethoxysilane in alcohol-alkali-water solution.SiO_2/β-Zn_4Sb_3 nanocomposite thermoelectric materials were fabricated with these core-shell composite particles by spark plasma sintering(SPS)method.Microstructure,phase composition,and thermoelectric properties of SiO_2/β-Zn_4Sb_3 nanocomposite thermoelectric materials were systemically investigated.The results show thatβ-Zn_4Sb_3 microparticles are uniformly coated by SiO_2 nanoparticles,and no any phase transformation reaction takes place during SPS process.The electrical and thermal conductivity gradually decreases,and the Seebeck coefficient increases compared to that ofβ-Zn_4Sb_3 bulk material,but the increment of Seebeck coefficient in high temperature range remarkably increases.The thermal conductivity of SiO_2/β-Zn_4Sb_3 nanocomposite material with 12 nm of SiO_2 shell is the lowest and only 0.56 W·m~(-1)·K~(-1)at 460 K.As a result,the ZT value of the SiO_2/β-Zn_4Sb_3 nanocomposite material reaches 0.87 at 700 K and increases by 30%.
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