Half-Heusler alloys are a potential thermoelectric material for use in high-temperature applications. In an attempt to produce half-Heusler thermoelectric materials with fine microstructures, TiCoSb was synthesized by the mechanical alloying of stoichiometric elemental powder compositions and then consolidated by vacuum hot pressing. The phase transformations during the mechanical alloying and hot consolidation process were investigated using XRD and SEM. A single-phase, half- Heusler allow was successfully produced by the mechanical alloying process, but a minor portion of the second phase of the CoSb formation was observed after the vacuum hot pressing. The thermoelectric properties as a function of the temperature were evaluated for the hot-pressed specimens. The Seebeck coefficients in the test range showed negative values, representing n-type conductivity, and the absolute value was found to be relatively low due to the existence of the second phase. It is shown that the electrical conductivity is relatively high and that the thermal conductivities are compatibly low in MA TiCoSb. The maximum ZT value was found to be relatively low in the test temperature range, possibly due to the lower Seebeck coefficient. The Hall mobility value appeared to be quite low, leading to the lower value of Seebeck coefficient. Thus, it is likely that the single phase produced by mechanical alloying process will show much higher ZT values after an excess Ti addition. It is also believed that further property enhancement can be obtained if appropriate dopants are selectively introduced into this MA TiCoSb System.

Half-heusler phase ZrNiSn is one of the potential thermoelectric materials for high temperature application. In an attempt to investigate the effect of Sb doping on thermoelectric properties, half-heusler phase () was synthesized by mechanical alloying of stoichiometric elemental powder compositions, and consolidated by vacuum hot pressing. Phase transformations during mechanical alloying and hot consolidation were investigated using XRD. Sb doped ZrNiSn was successfully produced in all doping ranges by vacuum hot pressing using as-milled powders without subsequent annealing. Thermoelectric properties as functions of temperature and Sb contents were evaluated for the hot pressed specimens. Sb doping up to x=0.04 in was shown to be effective on thermoelectric properties and the figure of merit (ZT) was shown to reach to the maximum at x=0.02 in this study.

Type I clathrate was produced by arc melting and hot pressing and thermoelectric properties were investigated. Negative Seebeck coefficient at all temperatures measured, which means that the majority carriers are electrons. Electrical conductivity decreased by increasing temperature and thermal conductivity was 0.012 W/cmK at room temperature and dimensionless thermoelectric figure of merit (ZT) was 0.01 at 873K.

Fe doped skutterudite CoSb3 with a nominal composition of FexCo1-xSb12 (0≤x≤2.5) have been synthesized by mechanical alloying (MA) of elemental powders, followed by vacuum hot pressing. Phase transformations during mechanical alloying and vacuum hot pressing were systematically investigated using XRD. Single phase skutterudite was successfully produced by vacuum hot pressing using as-milled powders without subsequent annealing. However, second phase of FeSb2 was found to exist in case of x≥2, suggesting the solubility limit of Fe with Co in this system. Thermoelectric properties as functions of temperature and Fe contents were evaluated for the hot pressed specimens. Fe doping up to x=1.5 with Co in FexCo4-xSb12 appeared to increase thermoelectric figure of merit (ZT) and the maximum ZT was found to be 0.78 at 525K in this study.

Ni-doped was prepared by the encapsulated induction melting and hot pressing, and its doping effects on the thermoelectric properties were investigated. Single phase was successfully obtained by the subsequent heat treatment at 773K for 24 hours. Nickel atoms acted as electron donors by substituting cobalt atoms. Thermoelectric properties were remarkably improved by the appropriate doping.

The encapsulated induction melting and hot pressing were employed to prepare Fe-doped skutterudites and their thermoelectric properties were investigated. Single phase was successfully obtained by the subsequent heat treatment at 773K for 24 hours. Iron atoms acted as electron acceptors by substituting cobalt atoms. Thermoelectric properties were remarkably improved by the appropriate doping. was found as an optimum composition for best thermoelectric properties in this work.

Undoped powders were synthesized by mechanical alloying (MA) of elemental powders using a nominal stoichiometric composition. Nano-structured, single-phase skutterudite was successfully produced by vacuum hot pressing (VHP) using MA powders without subsequent annealing. Phase transformations during synthesis were investigated using XRD, and microstructure was observed using SEM and TEM. Thermoelectric properties in terms of Seebeck coefficient, electrical conductivity, thermal conductivity and figure of merit(ZT) were systematically measured and compared with the results of analogous studies. Lattice thermal conductivity was reduced owing to increasing phone scattering in nano-structured MA , leading to enhancement in the thermoelectric figure of merit. MA associated with VHP technique offers an alternative potential processing route for the process of skutterudite.

Branched sulfonated poly(ether sulfone-ketone) copolymer was prepared with bisphenol A, 4,4-difluorobenzophenone, sulfonated chlorophenyl sulfone (40mole% of bisphenol A) and THPE (1,1,1-tris-p-hydroxyphenylethane). THPE was used 0.4 mol% of bisphenol A to synthesize branched copolymers. Organic-inorganic nano composite membranes were prepared with copolymer and a series of nanoparticles (20 nm, 4, 7 and 10 wt%). The composite membranes were cast from dimethylsulfoxide solutions. The films were converted from the salt to acid forms with dilute hydrochloric acid. The membranes were studied by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Sorption experiments were conducted to observe the interaction of sulfonated polymers with water and methanol. Branched copolymer and nano composite membranes exhibit proton conductivities from to , water uptake from 52.9 to 62.4%, IEC from 0.81 to 1.21 meq/g and methanol diffusion coefficients from to .