Ferroelectric properties of manganese doped (Bi1/2Na1/2)TiO3 and (Bi1/2Na1/2)TiO3–BaTiO3 epitaxial thin films

Abstract

The effects of Manganese doped (Bi1/2Na1/2)TiO3 and (Bi1/2Na1/2)TiO3–BaTiO3 epitaxial thin films on the structure, dielectric, ferroelectric and piezoelectric properties are reported. The thin films were grown by pulsed laser deposition on (Lao.5Sr0.5)CoO3 (LSCO) electrode LaAlO3 (LAO) substrates using homemade ceramic targets. The (La0.5Sr0.5)CoO3 (LSCO)/LaAlO3/system was chosen based on the adequate coupling conditions to grow high quality epitaxial films with desired properties. The dielectric and ferroelectric properties are all self-consistent to each other, despite the morphotropic phase boundary effect in Mn doped BNT-BT thin film. Even when remanent polarizations of 17 and 25μC/cm2 from BNT-Mn and BNT-BT-Mn thin films were respectively obtained from well-defined P–E hysteresis curves and the corresponding values of coercive field for BNT-Mn and BNT-BT-Mn thin films are 93 and 150kV/cm, respectively, no significant changes are observed suggesting that the effect of MPB composition is not fully activated due to Mn additions. In the ceramics, the vibrational modes associated to Mn interactions with the oxygen octahedral were identified with Raman spectroscopy. Finally, the local piezoelectric constants (d33) as measured by PFM are 60 and 124 pm/V for BNT-Mn and BNT-BT-Mn thin films, respectively. Thus, BNT-Mn and BNT-BT-Mn thin films are potential candidates to be used in lead-free piezoelectric devices.