Structural and dielectric properties of the lead-free (1−x)K0.5Na0.5NbO3–xSrTiO3 thin films from solutions

A. Kupec, B. Malic

Journal of Alloys and Compounds, 596 (2014) 32-38


The (1 − x)K0.5Na0.5NbO3–xSrTiO3 or (1 − x)KNN–xSTO, x = 0.025–0.25 thin films were deposited from the acetate-alkoxide-based precursor solutions with 10 mol% alkali-excess on Pt(1 1 1)/TiO2/SiO2/Si substrates. Depending on the amount of the two constituent phases, the bulk ceramic material has been reported to exhibit ferroelectric or relaxor behavior.

According to XRD, the films crystallized in perovskite phase upon heating at 750 °C. By increasing the STO content in the films, the monoclinic distortion, the volume of the unit cell and the degree of preferential (1 0 0) orientation decreased. The latter was explained as due to the differences in the average surface charges of the KNN and STO end members in the system. The microstructures of KNN–STO films consisted of small, equiaxed grains, of about 60 nm across notwithstanding the composition. The dielectric permittivity-maximum versus temperature decreased with increasing STO content in the films, and it was observed that the respective values were lower than those reported for bulk materials. The 0.925KNN–0.075STO film exhibited a typical relaxor behavior with a slim polarization–electric field loop.

Keywords: Lead-free; Chemical solution deposition; Thin film; Alkali niobate


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