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Effect of substrate on phase formation and surface morphology of sol-gel lead-free KNbO3, NaNbO3, and K0.5Na0.5NbO3 thin films

Helena Bruncková, Ľubomír Medvecký, and Pavol Hvizdoš

Institute of Materials Research, Slovak Academy of Sciences, Watsonova 47, 040 01 Košice, Slovakia



Abstract: Environmentally acceptable lead-free ferroelectric KNbO3 (KN) or NaNbO3 (NN) and K0.5Na0.5NbO3 (KNN) thin films were prepared using a modified sol-gel method by mixing potassium acetate or sodium acetate or both with the Nb-tartrate complex, deposited on the Pt/Al2O3 and Pt/SiO2/Si substrates by a spin-coating method and sintered at 650°C. X-ray diffraction (XRD) analysis indicated that the NN and KNN films on the Pt/SiO2/Si substrate possessed a single perovskite phase, while NN and KNN films on the Pt/Al2O3 substrate contained a small amount of secondary pyrochlore phase, as did KN films on both substrates. Scanning electron microscopic (SEM) and atomic force microscopic (AFM) analyses confirmed that roughness R q of the thin KNN/Pt/SiO2/Si film (≈ 7.4 nm) was significantly lower than that of the KNN/Pt/Al2O3 film (≈ 15 nm). The heterogeneous microstructure composed of small spherical and larger needle-like or cuboidal particles were observed in the KN and NN films on both substrates. The homogeneous microstructure of the KNN thin film on the Pt/SiO2/Si substrate was smoother and contained finer spherical particles (≈ 50 nm) than on Pt/Al2O3 substrates (≈ 100 nm). The effect of different substrates on the surface morphology of thin films was confirmed.

Keywords: sol-gel – (K,Na)NbO3 thin films – spin-coating – pyrochlore – perovskite phase – morphology

Full paper is available at

DOI: 10.2478/s11696-012-0190-y


Chemical Papers 66 (8) 748–756 (2012)

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