ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Effect of substrate on phase formation and surface morphology of sol-gel lead-free KNbO₃, NaNbO₃, and K_0.5Na_0.5NbO₃ thin films

Helena Bruncková, Ľubomír Medvecký, and Pavol Hvizdoš

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

E-mail: hbrunckova@imr.saske.sk

Abstract: Environmentally acceptable lead-free ferroelectric KNbO₃ (KN) or NaNbO₃ (NN) and K_0.5Na_0.5NbO₃ (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 www.springerlink.com.

DOI: 10.2478/s11696-012-0190-y

Chemical Papers 66 (8) 748–756 (2012)