Fracture mode, microstructure and temperature-dependent elastic moduli for thermoelectric composites of PbTe-PbS with SiC nanoparticle additions

• Published in: Philosophical magazine (Abingdon, England) Vol. 93; no. 35; pp. 4412 - 4439
• Main Authors: Ni, Jennifer E., Case, Eldon D., Schmidt, Robert D., Wu, Chun-I, Hogan, Timothy P., Trejo, Rosa M., Lara-Curzio, Edgar, Kanatzidis, Mercouri G.
• Format: Journal Article
• Language: English
• Published: Abingdon Taylor & Francis 01.12.2013
• Subjects: Annealing; Applied sciences; Cross-disciplinary physics: materials science; rheology; elastic properties; Elasticity. Plasticity; Exact sciences and technology; Materials science; Mechanical properties and methods of testing. Rheology. Fracture mechanics. Tribology; Metals. Metallurgy; nanocomposites; Nanoscale materials and structures: fabrication and characterization; Other topics in nanoscale materials and structures; Physics; porosity; Powder metallurgy. Composite materials; Production techniques; Surface treatment; Technology; thermoelectric; Temperature dependence; Scanning electron microscopy; Elastic modulus; Grain growth; Nanoparticle; Temperature effect; Annealing temperature; Powder metallurgy; Contamination; Composite material; Surface treatment; Thermoelectric materials; Hot pressing; Sintering; Porosity; Microstructure; Thermal annealing; Electric current; Nanostructured materials; Pulse current; Fracture mode; Ultrasonic method
• ISSN: 1478-6435; 1478-6443
• DOI: 10.1080/14786435.2013.833354

Twenty-six (Pb 0.95 Sn 0.05 Te) 0.92 (PbS) 0.08-0 .055% PbI 2 -SiC nanoparticle (SiC np ) composite thermoelectric specimens were either hot pressed or pulsed electric current sintered (PECS). Bloating (a thermally induced increase in porosity, P, for as-densified specimens) was observed during annealing at temperatures >603 K for hot-pressed specimens and PECS-processed specimens from wet milled powders, but in contrast seven out of seven specimens densified by PECS from dry milled powders showed no observable bloating following annealing at temperatures up to 936 K. In this study, bloating in the specimens was accessed via thermal annealing induced changes in (i) porosity measured by scanning electron microscopy on fractured specimen surfaces, (ii) specimen volume and (iii) elastic moduli. The moduli were measured by resonant ultrasound spectroscopy. SiC np additions (1-3.5 vol.%) changed the fracture mode from intergranular to transgranular, inhibited grain growth, and limited bloating in the wet milled PECS specimens. Inhibition of bloating likely occurs due to cleaning of contamination from powder particle surfaces via PECS processing which has been reported previously in the literature.