Research On The Lattice Dynamics Of Filled Skutterudite And Design Optimization Of Thermoelectric Module

With the development of social economy, energy shortage and environmental pollutionhave become increasingly severe. Thermoelectric (TE) generator, as a clean and sustainableenergy source, has been attracting attention widely since it can transfer waste heat toelectricity directly. However, the relatively low figure of merit values of thermoelectricmaterials have restricted the promotion and application of thermoelectric generator. Ourformer research has shown that compared to the single-flling, the In, Yb double-fllingapproach can optimize the thermoelectric properties more effectively. Here in order to probethe influence of double-filling on the thermal transport mechanism, the low-temperaturespecific heat capacities of filled skutterudite InxYbyCo4Sb12have been measured and analyzedin the context of combined electronic specifc heat (the Sommerfeld term), the Debye mode(long wavelength acoustic phonon modes), and the Einstein modes (localized vibrationmodes). It is concluded that the Einstein mode with lower-frequency comes from the extrafller atoms, confrmed by the results of inelastic neutron scattering measurements. The otherwith higher-frequency may originate from the motion of Sb atoms. After that, thelow-temperature lattice thermal conductivities of In0.1YbyCo4Sb12have been analyzed basedon the combination of Debye approximation and resonance scattering model. It is found thatfilling these two types of guest atoms with different eingenmode frequencies into the voids inskutterudites could introduce strong point defect and resonant scattering to lattice phonons,thus leads to significant decrease in the lattice thermal conductivity.Besides the property enhancement of thermoelectric materials, structure parameteroptimization of TE generator is also very important to obtain best performance. Based onwell-known TE theories, the correlation of output power and effieiency with size parameters l(length) and A/l (ratio of area to length)，has been simulated for a single TE module composedof P-type CeFe3CoSb12and N-type In0.2Yb0.2Co4Sb12using Matlab programming software,and optimized size parameters have been obtained. Furthermore, a model considering contacteffect has been established. The results show that the module is able to produce a maximumefficiency of5.03%in ideal contact condition when the temperatures of the cold and hot sidemaintained at30℃and330℃respectively. Contact effect simulation has revealed that asthe length of the thermocouple decreases, contact effect increases and the standard deviationof calculated output power increases significantly. The efficiency of the TE device rises firstly,keep steady and then go downward as the load resistance increases. In addition, with thecontact thermal resistance and electrical resistance increase, the device efficiency declines and the decline shows an increasing trend.