Piezoelectric Properties of Polar-Axis-Oriented Ferroelectric Bi4-xPrxTi3O12 Thick Films

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The piezoelectric response of 1.2-μm-thick Bi4-xPrxTi3O12 (BPT, $x=0.3$, 0.5, 0.7) ferroelectric films with polar-axis orientation is reported. Utilizing a long-range lattice-matching character, BPT films were grown by chemical solution deposition (CSD) on (101)-oriented IrO2 layers which were formed by the oxidation of Ir bottom layers during solution depositions. An effective piezoelectric coefficient $d_{33}=36$ pm/V comparable to that of Bi4Ti3O12 (BIT) single crystal was measured in BPT thick films with $x=0.3$. Related to the decrease in $P_{\text{s}}$, the total strain $\varepsilon_{\text{total}}$ decreased with increasing $x$. Stripe-shaped domain structures of ${\sim}20$ nm in width were observed in some grains in BPT thick films by piezoresponse force microscopy (PFM) and transmission electron microscopy (TEM). These structures could be attributed to 90° domain walls. The reconfiguration of these domains by the elecric field may occur to contribute to the ferroelectric polarizations resulting in a large value of $P_{\text{sat}}=50$ μC/cm2 in BPT thick films with $x=0.3$.
2004-09-15