Synthesis, characterization, and novel thermoelectric properties of Nb-based metal oxides XNb₂O₆ (X = Mg, Ca, Ba) for energy harvesting applications: Experimental and DFT insight

The structural, electronic, and thermoelectric properties of Nb-based metal oxides XNb₂O₆ (X = Mg, Ca, and Ba) have been investigated using DFT and experimental methods for energy harvesting applications. The XRD confirmed the orthorhombic structure of the synthesized oxides. SEM observed the formation of well-shaped particles, and the presence of Mg, Ca, Ba, Nb, and O with the proper compositions was confirmed by EDS. TEM proved the polycrystalline nature of sample BaNb₂O₆. The metal oxides MgNb₂O₆, CaNb₂O₆, and BaNb₂O₆ showed band gaps of 2.19 eV, 2.13 eV, and 0.90 eV, respectively. The calculations of the total and partial density of states were carried out to examine the effects of atomic orbitals on the formation of bands. The BoltzTraP algorithm within the Wien2k code was used to study the novel transport properties. The productive values of the figure of merit suggest that the studied materials are suitable for thermoelectric applications.