Combinatorial Approach For Screenning And Optimization Of Ge-Sb-Te Thermoelectric Materials

Due to the problem of energy shortages and the increasing environmental pollution caused by fossil energy combustion,thermoelectric conversion technology has been widely concerned as an environment-friendly energy conversion technology.The research on new thermoelectric materials is one of the high concern fields.However,the common method of material research is to prepare a sample of one component each time,while the combinatorial approachcan study of a component system,which uses high-throughput preparation combined with high-throughput characterization techniques for quick build the relationship between material composition,structure and performance.The combinatorial approaches can improve the efficiency of obtaining information in experiment and rapidly shorten the development cycle of new materials and products.According to these advantages mentioned above,the combinatorial approached have been widely applied in catalysis,pharmaceutical,luminescent materials and other fields.In order to search for new high-performance thermoelectric materials,the potential thermoelectric materials can be effective tested and selected through the combinatorial approaches.However there are little papers about the combinatorial approaches applied in thermoelectric materials.This paper will expand the application of composite materials in the field of thermoelectric materials research,providing a fast,efficient and low-cost approach to screening and optimization of thermoelectric materials quickly.In this paper,Ge-Sb-Te-based compound system was chosen to be the research object.In order to acquire thermoelectric samples with various composition and structure,the preparation method of melting method and plasma activated sintering method were exploredsystematically.The relationships between the chemical composition,the crystal structure and the thermoelectric properties in the combined sample were beingcharacterization and analysis,which revealed the relationship between the composition,structure and properties of the thermoelectric materials.The goal of screening outhigh-performance Ge-Sb-Te-based new compounds can be achieved.The main content and conclusion of this paper as follow:The Ge-Sb-Te-based sample library has been prepared by high temperature melting and annealing,the Seebeck coefficientdistributions were measured bySeebeck Probe microscope（PSM）with high-throughput characterization.The sample library prepared by the melting method contains a plurality of known phases and possible new phases,which achieves the purpose of diversifying the composition of the sample pool.The high-throughput characterization of the Seebeck coefficient was performed using the PSM device and the problems in the sample seebeck coefficient test were determined:the density of the ingot prepared by the melting and annealing method is low,and the surface defects and holes can lead to poor contact between the PSM probe and the sample,which makes the Seebeck coefficient with errors.This finding provides guidance for further optimization of the density of the sample library and the accuracy of high-throughput characterizationimproving.GeTe-Sb₂Te₃ binary diffusion couple was prepared by plasma activation sintering,hot pressed sintering and annealing.The parameters such as holding time,temperature and pressure were controlled to obtain the composition and structure of the sample.The properties of the microstructure,crystal structure and thermoelectric properties of the micro-domains were discussed.The relationship between the composition-structure and properties was constructed,and the new compounds of Ge-Sb-Te-based compounds with excellent thermoelectric properties were screened out.The optimal composition of the optimal Seebeck coefficient in the sample library is close to Ge_33.1Sb_13.7Te_53.2.The screened materials were prepared by molten-sintering method.The results showed that Ge_42.7Sb_5.5Te_51.8,Ge₃₈Sb_10.3Te_51.71.7 and Ge_36.5Sb_11.2Te_52.3（Sb content is relatively low）show similar to GeTe crystal structure and electric and thermal transport properties.Ge₂₇Sb_19.3Te_53.7,Ge₂₀S_b25Te₅₅5 and Ge_15.5Sb₂₈Te_56.5are composite phases containing Ge₂Sb₂Te₅ and Ge_0.95Sb₂Te₄.The results show that the change of Sb content can significantly affect the crystal structure and electric transport performance of the material.Among them,Ge₃₈Sb_10.3Te_51.71.7 in the prepared samples showed the most excellent thermoelectric properties,and achieved a maximumZT of1.35at 773 K.