Thermoelectric Properties of Bismuth Telluride Compounds Synthesised from Nigerian Ore Sources for Waste Heat Recovery in Metallurgical Furnaces

This study synthesises and characterises bismuth telluride-based thermoelectric compounds using bismuth sourced from trace mineral processing by-products and tellurium from associated mineral fractions collected from gold and base metal deposits in North Central Nigeria, evaluating their performance for waste heat recovery applications in metallurgical furnaces. The enormous quantities of waste heat rejected by Nigerian steelmaking and cement kiln operations represent a largely untapped energy recovery opportunity, and thermoelectric generators require no moving parts and can be installed in challenging industrial environments. Bi2Te3-based compositions including Bi2Te3, Bi0.5Sb1.5Te3, and n-type Bi2Se0.3Te2.7 are synthesised by ball milling and spark plasma sintering. Thermoelectric transport properties including Seebeck coefficient, electrical conductivity, and thermal conductivity are measured from 300 to 600 K using ZEM-3 and laser flash diffusivity apparatus. The dimensionless figure of merit ZT and power factor are calculated. Microstructure and composition are characterised by SEM-EDX, XRD, and TEM, and the influence of SPS processing temperature on grain size, Te vacancy concentration, and ZT is systematically investigated. A prototype thermoelectric module is assembled from the best-performing composition and tested at the exhaust flue of a laboratory box furnace to validate power output. Findings show ZT values up to 1.12 at 380 K for Bi0.5Sb1.5Te3, suitable for low-to-medium grade waste heat recovery. Keywords: thermoelectric, bismuth telluride, waste heat recovery, metallurgical furnace, Nigeria.