Hydrothermal growth of piezoelectrically active lead-free (Na,K)NbO3-LiTaO3 thin films

Single phase, lead-free thin films based on the (Na,K)NbO3-LiTaO3 solid solution near the morphotropic phase boundary are grown hydrothermally at 130 degrees C for the first time. Formation of the unwanted Na-rich phase normally occurring during hydrothermal synthesis of solid solution powder was successfully averted in the film growth by the addition of small amounts of EDTA to the starting precursor solution, which also allowed better control of the film growth rate. The hydrothermally grown NKN-LT film was found to be ferroelectrically and piezoelectrically active, showing a piezoelectric constant (d(33)) of 25 pm V-1.