The layered oxyselenide BiCuSeO has attracted significant attention due to its ability to demonstrate low thermal conductivity and a high Seebeck coefficient. This research project involved the synthesis of Bi_1−xNa_xCuSeO_1−xF_x (x = 0, 0.05, 0.10, 0.15, and 0.20) ceramics using high-energy ball milling and cold isostatic pressing techniques. A comprehensive investigation was conducted to examine the influence of co−doping NaF on the thermoelectric properties of BiCuSeO ceramics. The substitution of Bi³⁺ with Na⁺ introduces a substantial number of holes, resulting in a remarkable improvement in the electrical conductivity and power factor. The conductivity was significantly increased from 9.10 S cm⁻¹ (BiCuSeO) to 94.5 S cm⁻¹ (Bi_0.85Na_0.15CuSeO_0.85F_0.15) at 323 K. Additionally, at 823 K, the power factor of the Bi_0.85Na_0.15CuSeO_0.85F_0.15 sample reached 44.8 × 10⁻⁵ W/m K². Furthermore, the Bi_1−xNa_xCuSeO_1−xF_x ceramics demonstrated a minimum thermal conductivity of 0.43 W m⁻¹ K⁻¹. Consequently, the Bi_0.85Na_0.15CuSeO_0.85F_0.15 sample achieved a maximum ZT value of 0.78, which is 7.09 times higher than that of the pure BiCuSeO sample (0.11).

The layered oxyselenide BiCuSeO has garnered significant interest because of its ability to exhibit low thermal conductivity and a high Seebeck coefficient. This study involved the preparation of Bi1−xNaxCuSeO1−xFx(x=0, 0.05, 0.10, 0.15, and 0.20) ceramics through the processes of high energy ball milling and cold isostatic pressing. A systematic study was conducted to investigate the impact of co−doping Na/F on the thermoelectric performance of BiCuSeO ceramics. Replacing Bi3+ with Na+ results in the introduction of a considerable amount of holes, leading to a notable enhancement in the electrical conductivity and power factor. The conductivity was significantly increased from 9.10 S cm−1 in the pure BiCuSeO to 94.5 S cm−1 in Bi0.85Na0.15CuSeO0.85F0.15 at 323 K. At 823 K, the power factor of the Bi0.85Na0.15CuSeO0.85F0.15 sample achieved 44.8×10−5 W/ m K2. Moreover, the Bi1−xNaxCuSeO1−xFx ceramics exhibit a minimum thermal conductivity of 0.43 W m−1 K−1. As a result, the Bi0.85Na0.15CuSeO0.85F0.15 sample achieves a maximum ZT value of 0.78, which is 7.09 times greater than that of the pure BiCuSeO sample (0.11) .