Modulation of electrical transport in calcium cobaltite ceramics and thick films through microstructure control and doping. Issue 9 (August 2021)

• Record Type: Journal Article
• Authors: Yu, Jincheng; Chang, Yabin; Jakubczyk, Ewa; Wang, Bing; Azough, Feridoon; Dorey, Robert; Freer, Robert
• Is Part Of: Journal of the European Ceramic Society. Volume 41:Issue 9(2021)
• Page Start: 4859
• Page End: 4869
• Publication Date: 2021-08
• Subjects: Calcium cobaltite -- Thick film -- Solid state reaction -- Screen printing -- Heat-treatment; Ceramic materials -- Periodicals; Composite materials -- Periodicals; Matériaux céramiques -- Périodiques; Composites -- Périodiques; Ceramic materials; Composite materials; Periodicals; Electronic journals; 666.05
• DOI: 10.1016/j.jeurceramsoc.2021.03.044
• Languages: English
• ISSNs: 0955-2219

Abstract

Highlights: The effects of cobalt deficiency on thermoelectric performance of solid state synthesized Ca2.7 Bi0.3 Coy O9+δ (y = 3.92, 3.96 and 4.0) bulk ceramics were investigated. The thermoelectric response of the textured screen-printed Ca2.7 Bi0.3 Co3.92 O9+δ thick films were efficiently tailored by controlling sintering conditions. The mechanism of the order-disorder transition in the structural grain arrangements near the interface was analyzed. Abstract: Ca3 Co4 O9 is a promising p-type thermoelectric oxide material having intrinsically low thermal conductivity. With low cost and opportunities for automatic large scale production, thick film technologies offer considerable potential for a new generation of micro-sized thermoelectric coolers or generators. Here, based on the chemical composition optimized by traditional solid state reaction for bulk samples, we present a viable approach to modulating the electrical transport properties of screen-printed calcium cobaltite thick films through control of the microstructural evolution by optimized heat-treatment. XRD and TEM analysis confirmed the formation of high-quality calcium cobaltite grains. By creating 2.0 at% cobalt deficiency in Ca2.7 Bi0.3 Co4 O9+δ, the pressureless sintered ceramics reached the highest power factor of 98.0 μWm −1 K -2 at 823 K, through enhancement of electrical conductivity by reduction of poorly conducting secondary phases. Subsequently, textured thick films of Ca2.7 Bi0.3 Co3.92 O9+δ were efficiently tailored by controlling the sintering temperature and holding time. Optimized Ca2.7 Bi0.3 Co3.92 O9+δ thick films sintered at 1203 K for 8 h exhibited the maximum power factor of 55.5 μWm −1 K -2 at 673 K through microstructure control.