Thermoelectric Properties of Reduced Polycrystalline Sr_0.5Ba_0.5Nb₂O₆ Fabricated Via Solution Combustion Synthesis

Abstract

The thermoelectric properties of bulk polycrystalline Sr0.5Ba0.5Nb2O6 (SBN50) fabricated via solution combustion synthesis (SCS) and reduced at temperatures of 900°C–1150°C were explored. The Seebeck coefficient (S) of all samples increased over the entire range of testing temperatures; a peak S value of −281 μV/K was obtained at 930 K for the sample reduced at 900°C. A metal‐insulator transition was observed in the electrical conductivity (σ) of samples reduced at 1000°C–1150°C, whereas only semiconducting electrical behavior was observed for the sample reduced at 900°C. An optimal balance between S and σ was achieved for the pellet reduced at 1000°C, which exhibited a maximum power factor of 1.78 μW/cm·K2 at 930 K. Over a temperature range of 300–930 K, the thermal conductivity (κ) of as‐processed and reduced (1000°C) SBN50 was found to be 1.03–1.4 and 1.46–1.84 W/m·K, respectively. A maximum figure of merit (ZT) of 0.09 was obtained at 930 K for the 1000°C‐reduced sample. X‐ray photoelectron spectroscopy revealed that the Nb2+ peak intensity increased at higher reduction temperatures, which could possibly lead to a distortion of NbO6 octahedra and a decrease in the Seebeck coefficient.

Filled oxygen‐deficient strontium barium niobates

“…and Dandeneau et al. in sufficiently reduced unfilled SBN via electron energy loss spectroscopy and in X‐ray photoelectron spectroscopy, respectively . In SBN and BNO, oxygen vacancies are necessary in that they are suspected to be electronically compensating and thus responsible for the mixed valence state in the Nb.…”

“…Indeed, the presence of Nb 4+ has been reported by Lee et al and Dandeneau et al in sufficiently reduced unfilled SBN via electron energy loss spectroscopy and in X-ray photoelectron spectroscopy, respectively. 18,29 In SBN and BNO, oxygen vacancies are necessary in that they are suspected to be electronically compensating and thus responsible for the mixed valence state in the Nb. In BTNO, the mixed valence is manifest by the 2 Ti 4+ in which the oxygen vacancy concentration is negligible.…”

Ceramics for Sustainable Energy Technologies with a Focus on Polymer-Derived Ceramics

“…Several candidate ceramic p-type materials have been investigated including calcium cobaltite, Ca 3 Co 4 O 9 . There are limited studies on n-type ceramics, one promising candidate being (Sr(Ba) Nb 2 O 6 ) (Dandeneau et al 2013). Current and potential applications for TE ceramics include the recovery of waste heat in industrial furnaces or incineration processes and the harnessing of electric energy from alternative renewable energy sources such as solar thermal or geothermal.…”

Raman spectroscopy study of reduced strontium barium niobate (SBN61) and hints of supergrowth or intergrowth structures

“…SBN was initially studied for its electro‐optic properties in its unreduced or doped forms. Recent work has now demonstrated that reduced SBN displays high electrical conductivity, a high Seebeck coefficient, and low thermal conductivity along the c ‐axis of polarization, making it an interesting candidate for thermoelectric applications. In the present paper, we have used Raman spectroscopy to identify the structural changes induced by the reduction process that introduces charge carriers.…”