Fabrication and Characterization of Nd-Substituted Bi4Ti3O12 Thin Films with $a$- and $b$-Axis Orientations by High-Temperature Sputtering

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$a$- and $b$-axis-oriented (Bi4-xNdx)Ti3O12 (BNT; $x = 0.5--1.0$) films with 0.3 and 3.0 μm thicknesses, respectively, were fabricated on conductive IrO2(101)/Al2O3(012) substrates at 650 °C by high-temperature sputtering. The BNT films on the IrO2 electrode were preferentially $a$- and $b$-axis-oriented. The 3.0-μm BNT samples with $x = 0.75--1.0$ maintained a stable leakage current density range of $2.8 \times 10^{-10}$–$6.5 \times 10^{-8}$ A/cm2 in the wide field range of 25–160 kV/cm. The remanent polarization ($P_{\text{r}}$) exhibited maxima (0.3 μm; $2P_{\text{r}} = 36$ μC/cm2, 3.0 μm; $2P_{\text{r}} = 53$ μC/cm2) at $x = 0.75$, regardless of film thickness. It is shown that the samples with $x = 0.75--1.0$ have relatively superior fatigue endurance due to a firm Bi/Nd–O bonding state formed with increasing Nd substitution.
2009-09-25