Improved environmental stability of thermoelectric ceramics based on intergrowths of Ca3Co4O9–Na0.75CoO2. Issue 8 (15th April 2021)

• Record Type: Journal Article
• Authors: Vengust, Damjan; Jančar, Bostjan; Sever, Tilen; Šestan, Andreja; Bobnar, Vid; Kutnjak, Zdravko; Daneu, Nina; Suvorov, Danilo; Spreitzer, Matjaž
• Is Part Of: Ceramics international. Volume 47:Issue 8(2021)
• Page Start: 11687
• Page End: 11693
• Publication Date: 2021-04-15
• Subjects: Composite materials -- Microstructure -- Transmission electron microscopy -- Thermoelectric; Ceramics -- Periodicals; Céramique industrielle -- Périodiques; Ceramics; Periodicals; Electronic journals; 666
• DOI: 10.1016/j.ceramint.2021.01.008
• Languages: English
• ISSNs: 0272-8842

Abstract

Abstract: Ceramics based on calcium and sodium cobaltates are promising high-temperature thermoelectric oxide materials with complementary advantages. Ca3 Co4 O9 is stable at high temperatures, whereas Na0.75 CoO2 can be easily processed as a textured ceramic with excellent thermoelectric properties. Na0.75 CoO2, however, lacks long-term stability and degrades in even a relatively mild humid environment. In this work, we present a novel approach to the synthesis of complex composite materials based on intergrowths of sodium and calcium cobaltates that have excellent thermoelectric performance and improved stability. We synthesized samples with the mixed composition (3-x)Ca3 Co4 O9 –4x(Na0.75 CoO2 ) in an over-pressured oxygen atmosphere. Samples with the mixed Ca–Na composition developed textured microstructures composed of intergrowths of both end-members, as revealed by transmission electron microscopy. We also examined the thermoelectric performance of the investigated materials after exposure to high humidity and found that the composition with x = 0.8 (Ca:Na = 2.75) has long-term stability.