Structural, transport and thermoelectric properties of Nb-doped CaLaMnO perovskite

Poly-crystalline perovskite-type (CaLaMnO  ) Ca0.95La0.05Mn1−xNbxO3Ca0.95La0.05Mn1−xNbxO3 (0.0≤x≤0.100.0≤x≤0.10) was synthesized using the conventional solid-state reaction method. Structural and morphological properties were studied by X-ray diffraction analysis (XRD) and scanning electron microscopy (SEM), respectively. Their transport and thermoelectric properties were studied from electrical resistivity ρ(T)ρ(T) and Seebeck coefficient S(T) measurements as a function of temperature and niobium content. The Rietveld analysis revealed a compound with orthorhombic structure, where their lattice parameters increase with the niobium content which is given by a distortion in octahedra MnO6. Electrical resistivity exhibits a semiconducting-like behavior, for low niobium contents (Nb≤0.03Nb≤0.03) the magnitude of the electrical resistivity decreases, reaching minimum values close to 0.1Ω− cm. Seebeck coefficient is negative in all studied temperature range. The temperature behavior of S(T) is interpreted in terms of variable range hopping (VRH   ) and Heikes model. From ρ(T)ρ(T) and S(T  ) measurements it was possible to calculate the thermoelectric power factor (PF), which reaches maximum values around 0.4μW/K2-cm. These values make these ceramics promising electronic thermoelectric materials.