High Thermoelectric Figure of Merit in p-Type (Bi2Te3)x − (Sb2Te3)1−x Alloys Made from Element-Mechanical Alloying and Spark Plasma Sintering

p-Type (Bi2Te3)x − (Sb2Te3)1−x alloys with high thermoelectric properties were fabricated for waste heat energy recovery by mechanical alloying followed by spark plasma sintering. The samples’ diffraction peaks, such as the (015) positions, were slightly shifted from high to low 2θ angles with decreasing Sb2Te3 content due to the occupation of Sb sites by Bi atoms in the crystal lattice. The electrical conductivity increased with (Sb2Te3) content due to an increase in carrier concentration. The sample with the nominal composition of (Bi2Te3)0.15 + (Sb2Te3)0.85 exhibited a maximum thermoelectric figure of merit, ZT of 1.3 ± 0.06 at 400 K, and 1.07 ± 0.06 at 300 K. This enhanced ZT was successfully achieved by increasing (Sb2Te3) content, which reduces intrinsic conduction at higher temperatures by increasing carrier concentration and band gaps. The enhanced thermoelectric performance of the (Bi2Te3)0.15 + (Sb2Te3)0.85 TE materials can provide exceptional benefits for power generation and cooling applications around 400 K.