Effect of grain size and orthorhombic phase of La doped BiFeO3 on thermoelectric properties

LaxBi1-xFeO3 perovskite is synthesized via coprecipitation method. XRD, Raman, FTIR, and XPS analysis confirms structural formation. The lattice changes were observed on La substitution which distorts the lattice towards phase change from R3C to Pbnm. The volatilization of Bi-cation from surface tends to form the oxygen vacancies. Intrinsically, oxygen vacancies compensated by changing the Fe3+ to Fe2+. Maximum electrical conductivity of BFO is 1.61 S/m at 703 K which is possibly volatile maximum Bi3+. Minimum thermal conductivity of 1.501 W/mK is obtained for 0.05LBFO at 703 K. P-type semiconducting behavior is observed from Seebeck and Hall measurements. As a result of difference in concentration of La, size of each particle decreases which in turn suppresses thermal transport. On the other hand, orthorhombic phase increases enhancing thermal conductivity after 0.05LBFO. Due to La doping, changes in figure of merit are observed in BFO and La doped BFO. Maximum figure of merit of 0.00023 at 703 K is obtained for BFO which is 6 times higher than the 0.1LBFO.(c) 2023 Elsevier B.V. All rights reserved.

Automated summary

LaxBi1-xFeO3 perovskite was synthesized via coprecipitation method. XRD, Raman, FTIR, and XPS analysis confirmed the structural formation. La substitution caused lattice changes, distorting it from R3C to Pbnm phase. The volatilization of Bi-cation from the surface resulted in oxygen vacancies, compensated by changing Fe3+ to Fe2+. The maximum electrical conductivity of BFO at 703 K was 1.61 S/m, possibly due to the volatilization of Bi3+. The minimum thermal conductivity of 1.501 W/mK was observed for 0.05LBFO at 703 K. P-type semiconducting behavior was observed from Seebeck and Hall measurements. The concentration of La impacted particle size and thermal transport, while the orthorhombic phase increased thermal conductivity. Changes in the figure of merit were observed in BFO and La doped BFO. The maximum figure of merit of 0.00023 at 703 K was obtained for BFO, which was 6 times higher than 0.1LBFO.