Effect of TiO2 Nanoparticle on the Structural and Electrical Properties of Nd0.67Sr0.33MnO3 /TiO2 Composites

In this work, (1-x) (Nd0.67Sr0.33MnO3): x (TiO2) composites with x = 0, 0.1, 0.2, 0.3 and 0.4 have been prepared to investigate the structural and electrical properties. Nd0.67Sr0.33MnO3 (NSMO) was synthesised via the solid-state reaction method before incorporated with TiO2. The addition of TiO2 nanoparticle as the secondary phase in manganite composite would favour the spin-polarized tunnelling near to the grain boundary and thus enhance the extrinsic magnetoresistance. Nevertheless, nanoparticle addition might contribute to substitution and diffusion with manganite compound as reported in literature. The effect of the TiO2 nanoparticle addition into NSMO composites has been examined by an X-ray diffractometer (XRD) and a four-point probe (4PP) system. From the thermogravimetric analysis (TGA), NSMO phase formation occurred in between 756.45 - 977.59 °C. XRD patterns showed that there is no peak shift when the TiO2 concentration increases. It can be deduced that TiO2 was segregated at the NSMO grain boundary region and its grain surface. However, a small amount of Ti atoms are expected to replace the Mn atoms in NSMO crystal system and has caused the increase in crystallite size. The electrical study showed that the presence of TiO2 nanoparticle and substitution of Ti in Mn sites have weaken the double exchange (DE) mechanism and suppressed the metal-insulator transition temperature (TMI). In addition, the insulating behaviour of TiO2 has also caused the resistivity of composites to increase drastically.