Large Piezoresponse and Ferroelectric Properties of (Bi0.5Na0.5)TiO3-(Bi0.5K0.5) TiO3-Bi(Mg0.5Ti0.5)O3 Thin Films Prepared by Chemical Solution Deposition

Bulk ceramic 72.5mol%(Bi0.5Na0.5)TiO3-22.5mol%(Bi0.5K0.5)TiO3-5mol%Bi(Mg0.5Ti0.5)O-3 (BNT-BKT-BMgT) has previously been reported to show a large high-field piezoelectric coefficient (d(33)*=570pm/V). In this work, the same composition was synthesized in thin film embodiments on platinized silicon substrates via chemical solution deposition. Overdoping of volatile cations in the precursor solutions was necessary to achieve phase-pure perovskite. An annealing temperature of 700 degrees C resulted in good ferroelectric properties (P-max=52C/cm(2) and P-r=12C/cm(2)). Quantitative compositional analysis of films annealed at 650 degrees C and 700 degrees C indicated that near ideal atomic ratios were achieved. Compositional fluctuations observed through the film thickness were in good agreement with the existence of voids formed between successive spin-cast layers, as observed with electron microscopy. Bipolar and unipolar strain measurements were performed via double laser beam interferometry and a high effective piezoelectric coefficient (d(33,f)) of approximately 75pm/V was obtained.