Rare Earth-Substituted BI 4Ti3O12 Nanocrystalline Thin Films: Synthesis and Ferroelectric Characterization
M.S. Tomar, S. Dussan- Devia, R.S. Katiyar and O. Perales-Perez
University of Puerto Rico Mayaguez Campus, PR
bismuth layer structured ferroelectric, nanocrystalline thin film, sol-gel, Bi4Ti3O12
In this work we present the synthesis of bare and rare earth (Ce,Er,Pr)-doped Bi4Ti3O12 (BIT) nanocystalline thin films using a method based on the Sol-Gel process. Thin films were deposited by spin coating on Pt (Pt/TiO2/SiO2/Si) substrates annealing at 750°C.The XRD patterns revealed polycrystalline materials with formation in layered-perovskite. The average crystal size was estimate to be between 20-40 nm. The orthorhombic distortion b/a was 1.013, 0.990, and 0.977 for Ce, Er, and Pr, respectively for x = 0.55. The absence of the impurity phase in the XRD pattern suggests the incorporation of the dopant species in the BIT-host structure. The AFM images showed fairly uniform grains with average size 150 nm that consist of nanosize individuals. The “RMS” of the films (film thickness 400 nm) varies between 4nm and 13 nm. For a fraction of dopant (‘x’) of 0.55, the values of polarization and coercive field were 25.7 C/cm2 and 210 KV/cm, 22.82 C/cm2 and 195.73 KV/cm, 50.30 C/cm2 and 145.10 KV/cm for Ce, Er, and Pr dopants, respectively. The corresponding dielectric constants were 559, 394, 383, and 615. The loss dielectric varied between 6% and 20%. Leakage current of 10-7A/cm2 was below the value corresponding to pure films.
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Nanotech 2006 Conference Program Abstract