Characterization of the Piezoelectric Properties of Pb _0.98 Ba _0.02 (Mg _1/3 Nb _2/3 )O ₃ –PbTiO ₃ Epitaxial Thin Films

Pb(Mg _1/3 Nb _2/3 )O ₃ –PbTiO ₃ (PMN–PT) (70/30) thin films were deposited by pulsed laser deposition using two growth strategies: adsorption controlled deposition from lead‐rich targets (∼25–30 mass%) and lower‐temperature deposition ( T _d ≤600°C) from targets containing a small amount of excess lead oxide (≤3 mass %). The substrates used were (001) SrRuO ₃ /LaAlO ₃ . Typical remanent polarization values ranged between 12 and 14 μC/cm ² for these films. The longitudinal piezoelectric coefficient ( d _33,f ) was measured using in situ four‐circle X‐ray diffraction, and the transverse coefficient ( d _31,f or e _31,f ) was measured using the wafer flexure method. d _33,f and e _31,f coefficients of ∼300–350 pm/V and ∼−11 C/m ² were calculated, respectively. In general, the piezoelectric coefficients and aging rates were strongly asymmetric, suggesting the presence of a polarization bias. The large, extremely stable piezoelectric response that results from poling parallel to the preferred polarization direction is attractive for miniaturized sensors and actuators.