abstract
This paper reports a novel composite-based processing route for improving the electrical performance of Ca3Co4O9 thermoelectric (TE) ceramics. The approach involves the addition of metallic Co, acting as a pore filler on oxidation, and considers two simple sintering schemes. The (1-x)Ca3Co4O9/xCo composites (x = 0%, 3%, 6% and 9% vol.) have been prepared through a modified Pechini method, followed by one- and two-stage sintering, to produce low-density (one-stage, 1ST) and high-density (two-stage, 2ST) ceramic samples. Their high-temperature TE properties, namely the electrical conductivity (sigma), Seebeck coefficient (alpha) and power factor (PF), were investigated between 475 and 975 K, in air flow, and related to their respective phase composition, morphology and microstructure. For the 1ST case, the porous samples (56%-61% of rho th) reached maximum PF values of around 210 and 140 mu Wm(-1)K(-2) for the 3% and 6% vol. Co-added samples, respectively, being around two and 1.3 times higher than those of the pure Ca3Co4O9 matrix. Although 2ST sintering resulted in rather dense samples (80% of rho th), the efficiency of the proposed approach, in this case, was limited by the complex phase composition of the corresponding ceramics, impeding the electronic transport and resulting in an electrical performance below that measured for the Ca3Co4O9 matrix (224 mu Wm(-1)K(-2) at 975K).
keywords
SEEBECK COEFFICIENT; DEFECT CHEMISTRY; PHASE-EQUILIBRIA; POWER-FACTOR; WASTE HEAT; SOL-GEL; OXIDE; ENHANCEMENT; CERAMICS; OPTIMIZATION
subject category
Materials Science
authors
Constantinescu, G; Sarabando, AR; Rasekh, S; Lopes, D; Sergiienko, S; Amirkhizi, P; Frade, JR; Kovalevsky, AV
our authors
Andrei Kavaleuski
Principal Researcher
Artur Ricardo Mesquita Sarabando
research grante
Diogo João Breda Lopes
PhD Student
Gabriel Constantinescu
Researcher
Jorge Ribeiro Frade
Retired Professor
Parisa Amir Khizi
PhD Student
Sergii Sergiienko
Junior Researcher
Shahed Rasekh
Junior Researcheracknowledgements
This research was funded by the projects REMOTE (POCI-01-0145-FEDER-031875), CICECO-Aveiro Institute ofMaterials (UIDB/50011/2020 and UIDP/50011/2020) and SusPhotoSolutions (Centro-01-0145-FEDER-000005), financed by COMPETE 2020 Program and National Funds through the FCT/MEC and, when applicable, co-financed by FEDER under the PT2020 Partnership Agreement.