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Synthesis Of Nano-Skutterudite Compounds By Nonaqueous Coprecipitation Method

Posted on:2009-12-18Degree:MasterType:Thesis
Country:ChinaCandidate:Y L ChenFull Text:PDF
GTID:2121360245455148Subject:Materials science
Abstract/Summary:PDF Full Text Request
CoSb3 compounds have attracted attention widely, due to their large electrical conductivities and high Seebeck coefficients. Howerver, because of their thermal conductivity of CoSb3 compounds large, the conversion of thermo-electricity and ZT value are relatively low. Recently, in order to improve ZT value, the main researches are focus on doping including filling and substitution and on nanocrystallization. In this paper, we firstly explored the synthesis of nano-skuttterudite compounds by nonaqueous coprecipitation method, and the effect of synthesis process and doping on the nano-skuttterudite compounds powders were studied. We also preliminarily explored the effects of SPS sintering time and doping on the phase compositions, microstructure and electrical performance of nano-skuttterudite bulks.The starting reagents were SbCl3, CoCb3·6H2O, the ethanol and NaOH as solvent and precipitator respectively. Followed by drying, the precursor A composed of NaCl, amorphous antimony oxide and cobalt hydrate was obtained. Precursor A was washed, dispersed and dried, precursor B, which was composed of rhomboidal antimony oxide and amorphous cobalt hydrate, was obtained.The single phase CoSb3 powders were obtained after precursor A was heat treated, washed and dried. The quantity of precipitator, reduction temperature, reduction time, drying methods and doping may affect the phase compositions and the microstructure of the powders remarkably. When the precipitator is 1.2 times of theoretical value and the reduction condition is 350℃-1.5h, we obtained nanometer powders with size of about 10-20nm. The nickel doping had no obviously effects on the size of the powder particle, but the particle of the indium doping decreased.The single phase CoSb3 powders were obtained directly after precursor B was heat treated. The reduction temperature and the doping could affect the particle size of skutterudite. The particle size decreased with the rising reduction temperature. The size of powder was 50nm when precursor B was under 400℃-1h heat treatment. The nickel doping had no effects on the size of the powder particle, but the particle of the indium doping decreased, which were about 30-40nm.The powders of precursor A and B were both the single phase CoSb3, and the size of the former particles was about 30nm, which was smaller than that of the latter after the same heat treatment.Using the binary nano-size skutterudite and ternary skutterudite powders as starting materials, the skutterudite bulks with mean grains size of 100nm were obtained by SPS technology. The electrical properties have been improved by doping. The largest power factor value of 1.88×10-3Wm-1K-2 was obtained for the sample, that the doping amount of nickel was 1.0.
Keywords/Search Tags:skutterudite, nonaqueous coprecipitation, nano-powder, thermoelectric proporties
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