Papers by Keyword: Bismuth Antimony Telluride

Abstract: The aim of this experiment was to use mechanical chopper coupling with CO₂ laser ablation to reduce thermal effect on thermoelectric thin film fabrication. The average power at 10 W of sealed tube CO₂ laser together with the mechanical chopper was used for the thermoelectric (TE) thin film fabrication on silicon substrate in vacuum system. The 1.02 ms of pulse duration with 600 Hz of repetition rate were generated by the optimized speed of chopper at 4500 rpm with 8 channels of circular apertures which were used for the reduction of thermal effect on the bismuth antimony telluride (Bi-Sb-Te) target. The experiment results illustrated the thickness and the thin films fabricated by using 10 seconds of exposure time with the chopper, illustrated the smaller grain size than without the chopper while the thickness increased as the exposure time increased at constant speed of chopper. The output efficiency referred to the ratio of the thickness per target lost in unit time which increased from 19.6 to 181.8 μm/g per hour, due to the increase of the exposure time with the chopper while without the chopper resulted in 55.0 μm/g per hour caused by the higher temperature raise on the thermoelectric target which affected to the as-deposited thin films and the re-evaporation occurred. In this experiment, the chopper speed was measured by the digital tachometer, the target loss was analyzed by the digital analytical balance and the morphology of the 60⁰ tilted surface of thin film was characterized by scanning electron microscope (SEM).

Abstract: P-type BiSbTe/RuO₂ composite was fabricated using a combined process of melting and spark plasma sintering. The XRD patterns showed that RuO₂ reacted with the matrix for the RuO₂ content of 1.0 wt% and 4.0 wt% samples. The measured thermoelectric properties showed that the highest electrical conductivity was obtained for the sample with 2.0 wt% RuO₂. The power factor (α²σ/κ) decreased with the increase of RuO₂ below 450 K. The lattice thermal conductivity was lower than that of BiSbTe over the whole temperature range for BiSbTe/2.0 wt% RuO₂.

Abstract: Effect of Au (0-0.3 wt.%) on the thermoelectric properties of Bi1Sb3Te6 alloy prepared by mechanical alloying process has been investigated. The Seebeck coefficient decreases with Au content. The Seebeck coefficient of Au-free alloy at room temperature reaches a value of 250 µV/K, which is the maximum. Because of the increased power factor, the figure of merit increases with Au content up to 0.03 wt. % and its value at room temperature is about 2.8×10-3/K, the highest value among the prepared alloys. The Hall measurement shows that the carrier concentration increases with Au content, which explains the reason why the power factor has increased. The XRD patterns show that the intensities of (2 0 5), (0 0 18), (0 2 10), (1 0 19), (1 2 5), and (2 1 10) planes increase with Au content. The atomic distance of these complex planes is longer than that of other main planes, and the chemical bonding strength of these complex planes between constitutional elements is weaker than that of other main planes. As a result, a portion of electrons as minor carrier is trapped into accept level of Au atoms and/or clusters. The XPS observation result, which a portion of Au atoms is chemically shifted in contrast to Bi, Sb and Te atoms are not, explains that Au behaves as an acceptor.