Abstract
AbstractThe polycrystalline pellet of La2âxSrxCuO4 with x = 0.04, has been sintered using the solidâstate reaction process. Xâray diffraction (XRD) and field emission scanning electron microscopy (FESEM) have been carried out for microstructural characterizations. The transport properties (electrical and thermal) of La2âxSrxCuO4 for x = 0.04 have been investigated in the temperature range between 15 and 300 K with the aid of a closedâcycle refrigerator (CCR). The DC fourâprobe 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 holeâtype conduction and phononâdominated mobility with carrier concentration ~1018/cm3, which lie somewhere between nonâdegenerate 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 mixedâvalence heavy fermions systems. The steadyâstate method for thermal conductivity measurement has been employed. The plot of thermal conductivity (λ) as a function of temperature (T) shows a humpâlike structure at around 65 K, which may be attributed to an increase in the quasiâparticle 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 WiedemannâFranz 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.
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