Materials Science and Engineering A 445–446 (2007) 347–354 Characterization on the electrophoretic deposition of the 8 mol% yttria-stabilized zirconia nanocrystallites prepared by a sol–gel process Yueh-Hsun Lee a , Chih-Wei Kuo b , Chi-Jen Shih c , I-Ming Hung a , Kuan-Zong Fung a , Shaw-Bing Wen b , Moo-Chin Wang c,∗ a Department of Materials Science and Engineering, National Cheng Kung University, 1 Ta-Hsueh Road, Tainan 70101, Taiwan b Department of Resources Engineering, National Cheng Kung University, 1 Ta-Hsueh Road, Tainan 70101, Taiwan c Faculty of Fragrance and Cosmetics, Kaohsiung Medical University, 100 Shi-Chuan 1st Road, Kaohsiung 807, Taiwan Received 31 March 2006; received in revised form 5 September 2006; accepted 14 September 2006 Abstract An 8 mol% yttria-stabilized zirconia (8YSZ) films are electrophoretically deposited on the La 0.8 Sr 0.2 MnO 3 substrate using 8YSZ nanocrystallites prepared by a sol–gel process. Effects of liquid suspension on the particle zeta potential and degree of agglomeration at different pH values are investigated. When the pH value deviates from the point of zero charge (PZC), the adsorption of protons on particle surfaces cause higher zeta potential and well-dispersed suspension. The optimal values of the iodine concentration, applied voltage and deposition time for the electrophoretic deposition of 8YSZ films are also found. © 2006 Elsevier B.V. All rights reserved. Keywords: Electophoretic deposition; Nanocrystallites; Sol–gel processes; ZrO 2 ; Films 1. Introduction Yttria-stabilized zirconia (YSZ) is one of the most com- monly used high performance ceramic materials. Owing to its high ionic conductivity as well as thermal stability and excellent mechanical properties, YSZ ceramics are used in high temper- ature electronic devices such as oxygen sensor and solid oxide fuel cells (SOFC) [1]. To avoid the phase transformation dur- ing heating and cooling thermal cycles, YSZ ceramics with sole cubic symmetry, serving as the electrolyte materials of SOFC, are desired. In order to reduce operation temperature, a thinner electrolyte layer is required. Various physical or chemical processes such as electrochemical vapor deposition (EVD) [2], chemical vapor deposition (CVD) [3], physical vapor deposition (PVD) [4], plasma spraying [5], sol–gel method [6], colloidal deposition [7] and sputter deposition [8] have been performed to prepare YSZ thin films. Though these processes can prepare thin and dense coatings, they also reveal some disadvantages such as low ∗ Corresponding author. Fax: +886 6 2380208. E-mail address: cjshih@kmu.edu.tw (M.-C. Wang). deposition rate, expensive instruments, and critical production parameters. Except these process, electrophoretic deposition (EPD) is expected to exhibit the potential to fabricate thin and dense YSZ films. EPD has been received considerable attention in recent years, which is one of the colloidal processes for ceramic preparation [9,10]. The advantages of EPD include almost no restriction on substrate shape, a single deposition apparatus, and mass production. EPD consists of two steps: (i) electrophoresis, the motion of particles in a stable suspension under the influ- ence of an electric field and (ii) deposition, the coagulation of a dense layer of particles on the electrode. The uncomplicated and low-cost process makes EPD more economical for forming ceramic components. Ishihara et al. [11] have reported the preparation of YSZ films via EPD, on the platinum-coated nickel-CaO stabilized ZrO 2 and LaMnO 3 substrates. However, the effect of deposition conditions on the deposition behavior on the La 0.8 Sr 0.2 MnO 3 substrate, which is commonly used as a cathode material for SOFC, has not yet been reported in detail. In our previous work, the effect of Y 2 O 3 addition on the phase transition and growth of YSZ nanocrystallites has been dis- cussed [12]. The crystal structure of YSZ nanocrystallites varies 0921-5093/$ – see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.msea.2006.09.049