Lead-free piezoelectric 0.95(Na0.49K0.49Li0.02)(Nb0.8Ta0.2)O3–0.05CaZrO3 with 2 wt % MnO2 addition was prepared using mechanochemically-assisted solid-state synthesis. Upon mechanochemical activation of the mixture of reagents partial amorphization occurs which contributes to a significantly lower temperature of completion of the solid-state reaction, ~600 °C as opposed to ~700 °C for the conventional solid-state synthesis as determined by thermal analysis. The ceramic specimens prepared by the mechanochemically-assisted route exhibit improved compositional homogeneity and slightly enhanced piezoelectric properties, achieved in a considerably shorter processing time compared to the conventional solid-state synthesis route, which was studied as a reference.
Barium strontium titanate thin films with different Ba/Sr ratios deposited by radio-frequency magnetron sputtering are studied with respect to their composition using in situ X-ray photoelectron spectroscopy. The deposited samples can be described as either titanium-rich or stoichiometric, with cation B/A ratios (i.e., ratios between the Ti and (Ba þ Sr) concentrations) of 1.2-1.6 or 0.7-1.0, respectively. Volume sensitive compositional analysis using transmission electron microscopy shows a non-stoichiometry, which is less pronounced than at the surface. X-ray diffraction only shows cubic perovskite reflections. Together with photoelectron binding energy differences and full widths at half maxima of the Ti 2p and O 1s emissions, this indicates that all films consist of a single phase. The relation between oxygen concentration and B/A ratio further indicates that the deviation of stoichiometry is accommodated by removal or insertion of (Ba,Sr)O. The higher variation of (Ba,Sr)O content near the surface as compared to the bulk may be associated to an increased strain, which is proposed to contribute to surface roughening.
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