NZF-BT COMPOSITES: A PHOTOLUMINESCENCE APPROACH

Abstract

Photoluminescence (PL) analysis provide us important information about the structure of materials, however the PL behavior of (x)Ni0.7Zn0.3Fe2O4-(1-x)BaTiO3 ((x)NZF-(1-x)BT) multiferroic composites is not very well know. Based on this, (x)NZF-(1-x)BT powders whit different ratio of NZF/BT (x= 0.1, 0.3, 0.5, 0.7, 0.9) were synthesized by auto-combustion method. After that, the PL property of the composites was explored through measurements carried out using as excitation source a krypton laser with wavelength of 350 nm. The presence of PL emission suggests that the structures of the materials are medium range disordered. Oxygen vacancies (anion vacancies), metal vacancies (cation vacancy) and lattice distortion are responsible by PL emission due to formation of structural defects which are essential to promote the electronic transitions inside band gap. Emission at low energy (green/yellow/red) occurs due to deep defects which modify the Fermi level generating intermediary levels near the conduction band. On the other hand, PL emission at high energy region (violet/ blue) is originated by the presence of shallow defects which generate states next to the valence band. In the present work, all samples showed a broad band emission centered around 450 nm (Figure 1), being a region characteristic of contribution of shallow defects for photoluminescence emission. In addition, the PL broad band emission is an evidence of structural disorder in the lattice of materials which promotes the formation of numerous states within the band gap.