Physical properties of PdO addition and sintering temperature in Pr2/3Sr1/3MnO3 manganite

• Main Authors: Chian-Feng Lin, 林千夆
• Other Authors: yung-kang kuo
• Format: Others
• Published: 2015
• Online Access: http://ndltd.ncl.edu.tw/handle/38474113833108452131

碩士 === 國立東華大學 === 物理學系 === 103 === In this thesis, we report the investigation of the temperature-dependent magnetization (M), electrical resistivity (ρ), Seebeck coefficient (S), thermal conductivity (κ), and specific heat (CP) in the temperature range of 10 K to 350 K on Pr3/2Sr1/3MnO3 with various amount of PdO addition (0 - 30%) and different sintering temperature (1260 ℃ - 1450 ℃). Magnetization measurements show that these Pr3/2Sr1/3MnO3-based samples undergo a transition from paramagnetic to ferromagnetic phase at a well-defined Curie temperature TC ~ 280 K, regardless of the various amount of PdO addition or different sintering temperature. All samples show a clear metal-insulator transition in the vicinity of TC as revealed by electrical resistivity measurements. It is found that the electrical resistivity of Pr2/3Sr1/3MnO3 decreases with the addition of PdO. This can be attributed to the metallic Pd that resides within grain boundaries, providing additional channels for electrical conduction. All studied samples show a crossover from a small positive value of Seebeck coefficient at low temperatures to a negative value at higher temperatures. This positive to negative crossover is possibly due to the change in the nature of charge carriers from hole to electron with increasing temperature. The analysis of electrical reisitivity and Seebeck coefficient data indicates that the small polaron hopping model is operative in the high-temperature insulating region. The change in entropy associated with the transition as obtained from the specific heat measurements is found to increase with increasing sintering temperature, indicating an increase of magnetic homogeneity in these samples.