Structural characterization of NiTiO 3 nanopowders prepared by stearic acid gel method M.S. Sadjadi a , K. Zare a,b , S. Khanahmadzadeh a,c, ⁎, M. Enhessari a,d a Department of Chemistry, Science and Research Campus, Islamic Azad University, Hessarak, Tehran, Iran b Department of Chemistry, Shahid Beheshty University, Tehran, Iran c Department of Chemistry, faculty of science, Islamic Azad University, Mahabad Branch, Mahabad, Iran d Department of Chemistry, Islamic Azad University, Naragh Branch, Naragh, Iran ABSTRACT ARTICLE INFO Article history: Received 9 January 2008 Accepted 8 April 2008 Available online 13 April 2008 Keywords: Nickel titanate Wet-chemistry synthesis Nanopowders X-ray diffraction TEM FTIR Pure nickel titanate nanopowders were successfully prepared in wet-chemistry synthesis method, using nickel stearate and tetra-n-butyl titanate as Ni, Ti sources and stearic acid as complexing reagent. The gel was calcined at different temperatures in air ranging from 500 to 750 °C. Results of thermal analysis are given, including both DTG and TG. Fourier transform infrared spectrometry (FTIR), X-ray diffraction (XRD) and transmission electron microscopy (TEM) were used to characterize the crystallization process, the particle size and morphology of the calcined powders. The results indicated that nickel titanate nanopowders with particle size between 30 and 65 nm could be obtained after calcinations of the dried gel at 750 °C for 2 h. © 2008 Elsevier B.V. All rights reserved. 1. Introduction Titanium based oxides containing metals such as MTiO 3 (M: Ni, Pb, Fe, Co, Cu and Zn) are universally known as inorganic functional materials with wide applications. For example, they are applicable for industries, such as electrodes of solid oxide fuel cells, metal–air bar- riers, gas sensors and high performance catalysts [1–9]. Nickel titanate has been investigated as a tribological coating to reduce friction and wear at high temperature applications without using liquid lubricants [10–15]. The traditional preparation methods of NiTiO 3 can produce large NiTiO 3 particles with uncontrolled and morphologies due to their inherent problems such as high reaction temperature, heterogeneous solid phase reaction, etc. By contrast with the traditional methods, the wet-chemistry synthesis techniques, including sol–gel, sol–precipita- tion, combustion synthesis, chemical coprecipitation, and hydrother- mal synthesis, offer many distinctive advantages over traditional methods in the production of powders. There are few reports re- garding chemical synthesis of NiTiO 3 powders by citrate, maleate and propionic acid methods [13–18]. Thus, it is a meaningful work to investigate some routes at a low temperature to prepare ultra-fine particles of NiTiO 3 with a controlled morphology, a narrow size dis- tribution, and a high purity. In this study, we chose one typical wet-chemistry synthesis method, stearic acid gel, to try to prepare pure NiTiO 3 nanopowders. In this route, the carboxylic acid group and long carbon chain in stearic acid endow it with strong ability to disperse metal precursors. More- over, this synthetic process is easily controlled and convenient in comparison with other methods. 2. Experimental NiTiO 3 powders were prepared along a synthetic procedure as summarized in Fig. 1 . Nickel stearate, tetrabutyl titanate, and stearic acid used in experiments were all of analytical grade reagents. An appropriate amount of stearic acid was first melted in a beaker at 73 °C, and then a fixed amount of nickel stearate was added to the melted stearic acid and dissolved to form a green transparent solution. Next, stoichiometric tetrabutyl titanate was added to the solution, stirring to form a homogeneous light green sol, naturally cooling down to room temperature, and drying in an oven for 12 h to obtain dried gel. Finally, the gel was calcined at different temperatures in air to obtain nano-crystallites of NiTiO 3 . The formation of process and structural characterization of NiTiO 3 phases have been investigated by TG/DTA, FTIR, XRD, and TEM. Thermogravimetric/differential thermal analysis experiments were performed by TG/DTA (METTLER TA4000) in air to investigate the calcinations temperature and possible phase transformation from 25 to 900 °C with a heating rate of 5 °C/min. The FTIR spectrum was recorded with an MB100 (BOMEM) spectrometer by using KBr pellet. Materials Letters 62 (2008) 3679–3681 ⁎ Corresponding author. Department of Chemistry, faculty of science, Islamic Azad University, Mahabad Branch, Mahabad, Iran. Tel.: +98 442 2446534. E-mail address: Khanahmad_s@yahoo.com (S. Khanahmadzadeh). 0167-577X/$ – see front matter © 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.matlet.2008.04.028 Contents lists available at ScienceDirect Materials Letters journal homepage: www.elsevier.com/locate/matlet