Tunable ferroelectric domain orientation in polycrystalline and highly oriented Na0.5Bi0.5TiO3 Thin Films

Sodium bismuth titanate (Na0.5Bi0.5TiO3: NBT) has shown promising piezoelectric properties as an alternate to lead based piezoelectrics. NBT films with preferred crystalline orientation along <220> and polycrystalline features were fabricated on commercially available (111) Pt coated Si substrates by pulsed laser deposition (PLD). Ferroelectric domain patterns of NBT film with preferred orientation along <220> exhibited a variable in-plane piezoresponse in comparison to the out-of plane response. The presence of dominating planar components of the spontaneous polarization (Ps<111>) of NBT with rhombohedral structure could be responsible for the difference in planar response with respect to the sample alignment. In addition, a coherent interaction between polarization vectors across the grains was observed. However, the piezocoefficient (d33) measurements show that the oriented as well as polycrystalline film exhibits similar piezoresponse with an average value of ~25 pm/V.