Synthesis and Characterization of BNT thin films S. ABOU DARGHAM1,2,3 , J.JABBOUR1,3 ,Y.ZAATAR1,3 , J.ASSAAD2 , A.KHOURY1,3 , D.REMIENS 2 , D.ZAOUK 1,3 1
Platform for Research in Nanosciences and Nanotechnology, EDST, Lebanese University, B.P 90239 Fanar, Lebanon 2 IEMN - DOAE - MIMM Team, UVHC - Le Mont Houy - 59313 – Valenciennes, France 3 Applied Physics Laboratory, Faculty of Sciences II, Lebanese University, B.P 90656 Fanar, Lebanon
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[email protected] , denis.remiens@univ- valenciennes.fr
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Abstract: Polycrystalline piezoelectric lead- free Bi0.5 Na0.5 TiO3 (abbreviated as BNT) thin films were deposited on glass substrates by an optimized Sol-Gel process using the Electrospray technique. X-ray Diffraction (XRD) analysis showed that after heating the films at 650˚C for 1 hour, dense and well crystallized BNT films in the rhombohedral perovskite phase were formed. Polyhedral shaped primary particles, with an average size of approximately 200 nm and a smooth surface of 1.8 nm average roughness (Ra), were detected using AFM analysis. The deconvolution of Raman spectrum had confirmed our first results of XRD about the crystallization of BNT films due to the appearance of Raman peaks corresponding to the bending vibrations of Bi-O, Na-O and TiO 6 bonds. Index Terms: Piezoelectric, Sol-Gel, Electrospray, BNT. I. INTRODUCTION Recently, lead- free piezoelectric materials have been widely attracting attention as candidate materials in place PZT; one of those candidates is the Bismuth Sodium Titanate Bi0.5 Na0.5 TiO3 (BNT) [1-2]. In this paper, sol-gel-derived BNT thin films were deposited on glass substrates using the Electrospray technique, and their structural properties were studied using the X-ray Diffraction (XRD), Raman Spectroscopy and AFM. The effects of the processing conditions such as temperature of deposition and substrate-nozzle distance were investigated. II. EXPERIMENTAL DETAILS 1) Preparation of Sol precursor The sol precursor was obtained by using acetylacetone, titanium isopropoxide, bismuth nitrate and sodium nitrate dissolved in acetic acid. The mixture was stirred constantly until a transparent and stable yellow precursor solution was obtained. The obtained solution was then mixed with ethanol, diethanol Amine, deionized water and polyethylene glycol. 2) Electrospray process The flow rate of the precursor and the high voltage between substrate and nozzle are kept constant for all films deposition. After deposition, these films were heated at 650°C for 1 hour.
III. RESULTS AND DISCUSSION 1) Raman Spectroscopy The Raman spectra of BNT samples prepared at different deposition temperatures for a substratenozzle distance of 5 cm are shown in Fig. 1. The spectrum deconvolution using Gaussian functions, shows the vibration modes for BNT situated at 117 and 150 (Bi-O vibrations), 196 (Na-O-Ti), 250, 292 and 348 (Ti-O-Ti), 404 (TiO bending vibration), 528 (distortion TiO6) 628, 775 and 856 cm-1 (TiO 6 vibration) (Fig. 2). Fig.1: Raman spectra of the BNT thin films prepared for a substrate-nozzle distance of 5 cm.
2) X-ray diffraction XRD patterns of films prepared at different deposition temperatures for a substrate-nozzle distance of 5 cm are represented in Fig. 3. Films obtained are polycrystalline with a preferred orientation according to the (110) axis. This peak indicates the rhombohedral perovskite phase of BNT. The 50˚C is the optimal temperature for deposition since it shows the highest intensity for the (110) peak. Fig. 2: Raman spectrum decomposition.
3) Atomic Force Microscopy AFM characterization shows polyhedral shaped primary particles with an average size of 200 nm and a smooth surface of 1.8 nm average roughness (Ra). IV. CONCLUSION This preliminary study shows that electrospray combined sol-gel technique presents a new approach for the preparation of polycrystalline piezoelectric lead- free BNT.
Fig. 3: X-ray diffraction patterns of BNT films prepared at 5 cm.
REFERENCES [1] Yu, T., K. W. Kwok, et al. (2007). "Preparation and properties of sol–gel-derived Bi0.5 Na 0.5 TiO3 lead-free ferroelectric thin film." Th in Solid Films 515: 3563–3566. [2] QUIGNON, S. (2013). Synthèse et caractérisations de couches minces de matériaux piézoélectriques sans plomb , Université De Valenciennes Et Du Hainaut-Camb résis.
