Synthesis And Thermoelectric Properties Of FeVSb-based Thin Films

Recently,because the environmental pollution and energy shortage problems are being continuously accentuated,thermoelectric?TE?devices that can recover waste heat are achieving more and more attentions.TE devices can be divided into bulk TE devices and thin film TE devices.The thin film TE devices have some unique advantages such as flexibility,large heat pumping capacity,and precise temperature control at local regions.Therefore,the thin film TE devices attracts a lot of interest among the research community.FeVSb-based materials are environmentally friendly and low cost.In addition,FeVSb alloys show good TE properties with high conductivities and Seebeck coefficients.However,studies on FeVSb materials are usually about bulk alloys.The TE properties of the corresponding thin film materials have not been reported yet.This paper mainly studies the TE properties of FeVSb-based thin films prepared by magnetron sputtering.It is usually very challenging to systematically measure the in-plane TE properties of thin film materials.In this paper,the measurement methods on TE performance of thin film materials are introduced in detail.First,the step to measure the conductivity of thin films using the Van der Pauw method was described.Second,the modular test equipment was built using a rapid Seebeck coefficient test method.By comparing with constantan standard sample,the test error is suggested to be less than 8.5%.Moreover,the thermal bridge method to measure the in-plane thermal conductivity of the film was introduced detailed.In this paper,FeVSb-based thin films were deposited by magnetron co-sputtering.It was found that these thin films have a typical amorphous structure at a temperature?473 K.When the temperature is higher than 473 K,crystallinity occurs.The non-doped FeVSb film is an n-type semiconductor with a Seebeck coefficient of-42.3–-49.0?V/K and a power factor of 0.36–0.53 mWm^-1K^-2 at a temperature of 300–473 K.The Ti-doped?FeVSb?_1-xTi_x thin films are p-type semiconductors.Among them the?FeVSb?_0.94Ti_0.06 film has the highest Seebeck coefficient and power factor,whose Seebeck coefficient is 69.9–89.2?V/K,while the power factor is 0.70–1.19mWm^-1K^-2.The thermal conductivity of FeVSb and?FeVSb?_0.94Ti_0.06 amorphous films are 1.10 Wm^-1K^-1 and 0.99 Wm^-1K^-1 at temperatures of 300 K,respectively,using the thermal bridge method.The ZT values of FeVSb and?FeVSb?_0.94Ti_0.06 films are 0.09and 0.23,respectively.It indicates that the amorphous structure greatly reduces the thermal conductivity of the films and effectively improves the thermoelectric properties of the materials.Therefore,?FeVSb?_1-xTi_x amorphous films are promising TE thin film materials.An in-plane thin-film TE generator?TEG?based on?FeVSb?_1-xTi_x TE thin films material was fabricated.This TEG exploited FeVSb and?FeVSb?_0.94Ti_0.06 as the n and p-type TE legs,respectively.Conductive silver paste was used as electrodes.The TEG has an open circuit voltage of 15.4 mV and a maximum output power of 248 nW at a temperature difference of 59.4 K.By comparing the internal resistance of the TEG and the conductivity of as-deposited?FeVSb?_1-xTi_x thin films,it is suggested that the material selection and structural design of this in-plane thin film TEG are feasible.