Influence of silver nanoparticle addition, porosity, and processing technique on the mechanical properties of [Ba.sub.0.3][Co.sub.4][Sb.sub.12] skutterudites

• Published in: Journal of materials science Vol. 49; no. 20; pp. 7192 - 7212
• Main Authors: Schmidt, Robert D, Case, Eldon D, Lobo, Zayra, Thompson, Travis R, Sakamoto, Jeffrey S, Zhou, Xiao-Yuan, Uher, Ctirad
• Format: Journal Article
• Language: English
• Published: Springer 15.10.2014
• Subjects: Electric properties; Electrical conductivity; Mechanical properties; Methods; Porosity; Powders
• ISSN: 0022-2461; 1573-4803
• DOI: 10.1007/s10853-014-8427-5

The thermoelectric skutterudite [Ba.sub.0.3][Co.sub.4][Sb.sub.12] is a promising candidate for waste heat recovery applications. Recently, it was demonstrated that the addition of silver nanoparticles ([Ag.sub.NP]) to [Ba.sub.0.3][Co.sub.4][Sb.sub.12] increases both the thermoelectric figure of merit and electrical conductivity. This study is the first to examine the effect of [Ag.sub.NP] addition on the material's mechanical properties. This study also found that the Young's modulus, E, shear modulus, G, and bulk modulus, B, decreased linearly with increasing volume fraction porosity, P. Resonant ultrasound spectroscopy was employed to measure the elastic moduli, and Vickers indentation was used to determine the hardness, H, and fracture toughness, [K.sub.C]. Trends in the mechanical properties as a function of grain size, porosity, and the [Ag.sub.NP] are discussed in terms of the pertinent literature. While [K.sub.C] was independent of [Ag.sub.NP] addition, porosity, and grain size, both E and H decreased linearly with increasing porosity. In addition, this study is the first to identify (i) the [Ag.sub.3]Sb phase formed and (ii) the enhanced densification that occurs when the [Ag.sub.NP] is sintered with [Ba.sub.0.3][Co.sub.4][Sb.sub.12] powders, where both effects are consistent with the eutectic and peritectic reactions observed in the binary phase diagram Ag-Sb. These eutectic/peritectic reactions may also be linked to the enhancement of electrical conductivity previously observed when Ag is added to [Ba.sub.0.3][Co.sub.4][Sb.sub.12]. Also, similar beneficial eutectic/peritectic reactions may be available for other systems where conductive particles are added to other antimonides or other thermoelectric systems.