One of the materials able to exhibit a transition from insulators to metals (IMT materials) is vanadium dioxide (VO2). Through IMT, VO2 shows a drop of resistivity of five orders of magnitude at a picosecond timescale. In this work, the feasibility of using VO2 as an efficient thermal switching device is discussed. Several synthesis methods (sol-gel, hot press and spark plasma sintering) were attempted to obtain VO2 sample in pellet form. From the X-ray diffraction results, it was found that spark plasma sintering (SPS) yielded the highest phase purity. Several sintering parameters such as temperature or sintering time were tested to determine the optimal sintering conditions. For better thermal switching behavior, high-energy ball milling was used to reduce lattice thermal conductivity (k_(lat.)) in the insulator phase. Ball-milling time was varied from 30 minutes to 2 hours. It was found that with increasing milling time, the k_(lat.) was reduced. Thus, it was demonstrated that thermal switching behavior was most efficient with 2 hour-milling. To improve electronic thermal conductivity (k_(elec.)) in the metallic state, nano-sized copper particles were added to the VO2 system with a subtle amount variation ranging from 3at % to 5 at%. Results show that a composite with 5 at% Cu (copper) addition exhibited the largest increase in thermal conductivity (k) in the metallic state. In addition to this, a basic mechanism behind IMT and some of the exemplary IMT-based applications were introduced.
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