Thermoelectric properties of La1.96Sr0.04CuO4 for energy harvesting and storage applications

Abstract The polycrystalline pellet of La 2‐x Sr x CuO 4 with x = 0.04, has been sintered using the solid‐state reaction process. X‐ray diffraction (XRD) and field emission scanning electron microscopy (FESEM) have been carried out for microstructural characterizations. The transport properties (electrical and thermal) of La 2‐x Sr x CuO 4 for x = 0.04 have been investigated in the temperature range between 15 and 300 K with the aid of a closed‐cycle refrigerator (CCR). The DC four‐probe resistivity measurement confirms a decrease in resistivity with increasing temperature below 200 K. However, above 200 K, an increase in resistivity with temperature (metallic behaviour) has been noticed due to charge carrier localization. The Hall measurement conveys hole‐type conduction and phonon‐dominated mobility with carrier concentration ~10 18 /cm 3 , which lie somewhere between non‐degenerate and degenerate limit. The Seebeck coefficient also confirms hole type conduction and its temperature dependence can be explained in the light of the model applicable for mixed‐valence heavy fermions systems. The steady‐state method for thermal conductivity measurement has been employed. The plot of thermal conductivity ( λ ) as a function of temperature ( T ) shows a hump‐like structure at around 65 K, which may be attributed to an increase in the quasi‐particle mean free path. Further, the electronic and lattice (phononic) contributions to thermal conductivity have been separated using electrical conductivity data with the help of the Wiedemann‐Franz law. Our analysis confirms the phononic dominance in the thermal conductivity of the investigated sample. The figure of merit (ZT) estimated from the experimental data has a maximum value of 0.086 at 290 K and hence shows its inherent energy harvesting properties that can further be stored in a battery or capacitor.