The effect of Ho addition on electrical transport properties of LCMO" / Noorhasimah Yeop

This research is done to measure the "Effect of Holmium addition on the electrical transport properties of polycrystalline LCMO manganite". The different value of Ho which is at x = 0.00, 0.15, 0.30 was added to LCMO and grind it to make them mixed together. After that the entire sample was calcine at 900°C for 12 hours at the rate 3°C per minute. Then the sample was press to make it into a pellet and sinter at 1300°C. Then this sample was measure by using instruments such as four point probe and scanning electron microscope. I found that, the electrical resistivity as a function of temperature at zero field, p(0,T) for (Lai.xHox)o.67Cao.33Mn03 for x = 0.00,0.15,0.30 show semiconducting behavior above Tp and metallic behavior below Tp by usng four point probe. With increasing Ho doping, the metal-insulator transition temperature Tp shift to lower temperature and the resisitivity is increase which is for x = 0.00, TMI is 256 K with resistivity value 1.48 mQ.cm. While for x = 0.15, TMI was observed at 152 K with resistivity value 66.5 rafl.cm. For sample x = 0.30, TMI is 140 K with resistivity value 214 mfl.cm. the transport mechanism also can be explained by Double Exchange mechanism, Jahn Teller effect.and Jahn Teller polaron. The investigation of the grain size and examination of the composition of sample was done by using a Scanning electron microscope. It found that the Ho is coexisting with the pure LCMO. When the adding of Holmium is increasing, the brightness which is representing the Holmium is more clear to seen.