The electrical conductivity of the cubic phase, which is larger than that of the monoclinic phase, and similar thermal conductivities of the two phases lead to the higher ZT of the cubic Cu₂SnSe₃.

SnSe is considered as a promising thermoelectric (TE) material since the discovery of the record figure of merit (ZT) of 2.6 at 926 K in single crystal SnSe. It is, however, difficult to use single crystal SnSe for practical applications due to the poor mechanical properties and the difficulty and cost of fabricating a single crystal. It is highly desirable to improve the properties of polycrystalline SnSe whose TE properties are still not near to that of single crystal SnSe. In this study, in order to control the TE properties of polycrystalline SnSe, polycrystalline SnSe–SnTe solid solutions were fabricated, and the effect of the solid solution on the electrical transport and TE properties was investigated. The SnSe_1−xTe_x samples were fabricated using mechanical alloying and spark plasma sintering. X-ray diffraction (XRD) analyses revealed that the solubility limit of Te in SnSe_1−xTe_x is somewhere between x = 0.3 and 0.5. With increasing Te content, the electrical conductivity was increased due to the increase of carrier concentration, while the lattice thermal conductivity was suppressed by the increased amount of phonon scattering. The change of carrier concentration and electrical conductivity is explained using the measured band gap energy and the calculated band structure. The change of thermal conductivity is explained using the change of lattice thermal conductivity from the increased amount of phonon scattering at the point defect sites. A ZT of ~0.78 was obtained at 823 K from SnSe_0.7Te_0.3, which is an ~11% improvement compared to that of SnSe.

Stable slurries in dispersions of 3Y‐TZP in aqueous suspension with the addition of different concentrations of dispersants such as ammonium polyacrylate (APA) and diammonium citrate (DAC) were investigated. The dispersion properties were investigated by measuring the particle size, zeta potential, sedimentation, and viscosity as a function of the wt.% of the dispersant. Both dispersant agents were attached to the 3Y‐TZP surface by the carboxylic group, as shown by the FTIR results. The addition of dispersants was found to produce more dispersed and stabilized aqueous suspension. As shown the viscosity result, that there is no being viscosity peak has been occurring and viscosity going decrease as the shear rates increasing which mean that the suspension has shear thinning behavior and there is no agglomeration as the shear rate is increased. It was determined that 3.5 wt.% of DAC and APA produced the best and most stable slurry; when 3.5 wt.% of DAC and APA was added, the zeta potential showed the largest value in the monodisperse condition. The low pH value of DAC has obtained the higher zeta potential value than APA, which was assumed due to low pH of DAC suspension. At low pH, the adsorption of the adsorbate will occur in a flat adsorbed, while at higher pH the polyelectrolyte will dangle into solution, thus reducing electrostatic repulsion as it is found in the case of APA addition. In this condition, the particle size was decreased to the lower value and the slurry’s stability was obtained with the lowest sedimentation height after the sedimentation test for 30 days. The sample was milled in an attrition mill at 1,000 rpm for four hours.

A wide application of 3 mol% Yttria-stabilized Tetragonal Zirconia Poly-crystalline (3Y-TZP) makes the concern of ceramic processing required to produce strong and reliable engineering ceramic products. In this study, we successfully improved the 3Y-TZP mechanical properties by paying great concern to the early processing of 3Y-TZP powder. Here, we used the concept of colloidal processing by manipulating the 3Y-TZP inter-particle force as a combination of steric and depletion stabilization. Di-ammonium citrate (DAC) was used to induce steric stabilization utilizing the DAC’s carboxyl group to strongly bond with the OH group of the 3Y-TZP. While Polyvinylpyrrolidone (PVP) which could not bond with 3Y-TZP, leaves it freely as an un-attached polymer in slurries and induces a depletion stabilization mechanism. Using the combination of steric and depletion stabilization, the YSZ slurries stability is improved, and a uniform and smaller particle size can be obtained. As the result, better microstructure and high mechanical properties of the sintered body, such as higher density and Vickers hardness, can be achieved. By comparing to the sintered body of 3Y-TZP containing just DAC and 3Y-TZP containing a combination of DAC and PVP, better-sintered body properties can be found for the 3Y-TZP containing the combination of DAC and PVP, and the results can be listed as follows: grain size reduced from 0.420 to 0.281 um, density is increased from 94.5 to 99.3%, and Vickers hardness increases from 1190 to 1305 HV.