Processing and properties of ferroelectric relaxor lead scandium tantalate Pb(Sc_1/2Ta_1/2)O₃ thin films

Thin films of Pb(Sc_1/2Ta_1/2)O₃ (PST) were fabricated using an optimized chemical solution deposition procedure involving the de-hydration of scandium acetate and the addition of up to 30% excess lead in solution. The choice of substrate was found to impact the thermal induced stress in the films as confirmed by wafer bending and in-plane grazing angle x-ray diffraction measurements. The presence of either a compressive or a tensile in-plane stress led to a reduction in the temperature of the dielectric maximum, whereas the value of the dielectric maximum remained relatively unchanged; its value reduced by an order of magnitude compared with ceramic samples. It is concluded that mechanical stress alone is not the sole factor in the reduction of PST thin film permittivity. Microstructural features resulting from processing induced defects or an incomplete transformation to the relaxor state may be responsible for this commonly observed phenomenon.