Synthesis and characterization of nano-sized zirconia powder synthesized by single emulsion-assisted direct precipitation Navin Chandra * , Deepesh Kumar Singh, Meenakshi Sharma, Ravi Kant Upadhyay, S.S. Amritphale, S.K. Sanghi Advanced Materials and Processes Research Institute (CSIR), Habibganj Naka, Hoshangabad Road, Bhopal 462 064, MP, India article info Article history: Received 23 October 2009 Accepted 24 October 2009 Available online xxxx Keywords: t-ZrO 2 Phase transformation Reverse microemulsion X-ray diffraction (XRD) abstract For the first time, single reverse microemulsion-assisted direct precipitation route has been successfully used to synthesize tetragonal zirconia nanoparticles in narrow size range. The synthesized powder was characterized using FT-IR, XRD and HRTEM techniques. The zirconia nanoparticles obtained were spher- ical in shape and has narrow particle size distribution in the range of 13–31 nm and crystallite size in the range of 13–23 nm. Ó 2009 Elsevier Inc. All rights reserved. 1. Introduction Zirconia (ZrO 2 ) is a widely used ceramic material exhibiting excellent properties such as low thermal conductivity, high coeffi- cient of thermal expansion, high thermal stability, high oxygen ion conductivity, high strength, high fracture toughness and high ther- mal shock resistance enabling it to be used as thermal barrier coat- ing, cutting tools, refractory material, as catalyst/catalyst support (stable under a reducing atmosphere and photo irradiation). More- over, owing to their high oxygen ion conductivity, the high temper- ature phases (tetragonal and cubic) of ZrO 2 are useful as solid electrolytes in oxygen sensors and solid oxide fuel cells [1,2]. ZrO 2 is also used as ball heads for total hip replacement because of its good chemical and dimensional stability, mechanical strength, toughness and Young’s modulus [1]. About 95% of fer- rules used in optical fiber connectors are made of zirconia [3]. Be- cause of amphoteric nature, it can be used to modify the inner surface of fused silica capillary, which can be applied in separation science (capillary electrophoresis) to obtain switchable electro-os- motic flow [4]. Zirconia is stable over a wide pH range and has higher thermal stability, so surface modifications using zirconia nanoparticles may increase options in the development of analyt- ical methods. The isoelectric point of ZrO 2 depends on the nature of its crystallographic phase, which in turn decides the pH of the background electrolyte [5]. At atmospheric temperature and pressure, zirconia exists in monoclinic form, but with increase in temperature, it transforms to tetragonal at 1170 °C and cubic phase above 2370 °C. The appli- cation of pressure also causes phase transformation in zirconia; at 3 GPa, a Pbca-type orthorhombic phase occurs, which converts to Pnam at 16–22 GPa [6,7]. Orthorhombic structure is considered to be an intermediate structure between monoclinic and tetrago- nal. Transformation of tetragonal to monoclinic phase is accompa- nied by 3–5% increase in volume [8]. High temperature polymorphs (tetragonal and cubic) have to be stabilized at lower temperature because of their application in various fields, either by adding stabilizers such as Y 2 O 3 , MgO and CaO or by reduction in grain or particle size into nanometer regime [9]. Zirconia particles in the nano-size range have been synthesized using various routes such as sol–gel [1,10], co-precipitation [11,12], ball milling [13], hydrothermal process [14,15], gas phase synthesis and microemulsion methods [16–18]. Due to the possi- bility of controlling reactor (droplet) size, the emulsion method yields nanopowders with a narrow size range. Reverse microemul- sion is a transparent, isotropic and thermodynamically stable dis- persion of nano-sized aqueous droplets dispersed in a continuous oil phase, in the presence of interfacial film of surfactant mole- cules. The microemulsion methods reported in literature for the preparation of nano-sized zirconia powder may either involve preparation of a single emulsion followed by precipitation or prep- aration of two separate emulsions and their mixing followed by hydrolysis. For example, Feng et al. [19] used single as well double microemulsion system to synthesize zirconia particles. The former method produced larger particles with a mixture of tetragonal and monoclinic phases, while the latter yielded finer zirconia particles with tetragonal phase. Following two emulsions, dopant/stabilizer 0021-9797/$ - see front matter Ó 2009 Elsevier Inc. All rights reserved. doi:10.1016/j.jcis.2009.10.065 * Corresponding author. Fax: +91 755 2587042/2488323. E-mail addresses: navinchandrarrl@yahoo.com (N. Chandra), nit_d7@yahoo.com (D.K. Singh), meenakshirrl@yahoo.com (M. Sharma), rkupadhyay85@gmail.com (R.K. Upadhyay), ssamritphale@hotmal.com (S.S. Amritphale), sksanghi@ampri. res.in (S.K. Sanghi). Journal of Colloid and Interface Science xxx (2009) xxx–xxx Contents lists available at ScienceDirect Journal of Colloid and Interface Science www.elsevier.com/locate/jcis ARTICLE IN PRESS Please cite this article in press as: N. Chandra et al., J. Colloid Interface Sci. (2009), doi:10.1016/j.jcis.2009.10.065