Effects of neodymium doping on microstructures and ferroelectric properties of bismuth titanate ferroelectric thin films

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The Bi4-xNdxTi3O12(x=0.00,0.30,0.45,0.75,0.85,1.00,1.50) ferroelectric thin films were prepared on the Pt/Ti/SiO2/Si(100) substrates using sol-gel method. The effect of neodynium doping on the microstructures and ferroelectric properties of films were studied. The experimental results show that Nd3+ only substitutes Bi3+ in the pseudo-perovskite block when Nd content x is lower than 0.45. When Nd content x is about 0.45, the film has the largest remnant polarization (2Pr) of 32.7μC·cm-2 at an applied field of about 270kV·cm-1. At x>0.45, part of Nd ions are incorporated into the (Bi2O2)2+block, which would change the microstructure of (Bi2O2)2+ block and weaken its functions as the insulating layer and the space charge storage, resulting in the decrease of the 2Pr. When x=1.50, the dopout would destroy the structure of (Bi2O2)2+ block, which leads to ferroelectric-paraelectric phase transition of the film.