RESEARCH ARTICLE Copyright © 2005 American Scientific Publishers All rights reserved Printed in the United States of America Journal of Nanoscience and Nanotechnology Vol. 5, 1101–1107, 2005 TEM/AFM Investigation of Size and Surface Properties of Nanocrystalline Ceria S. Gupta, 1 P. Brouwer, 1 S. Bandyopadhyay, 1 ∗ S. Patil, 2 R. Briggs, 3 J. Jain, 4 and S. Seal 2 1 School of Materials Science and Engineering, The University of New South Wales, Sydney 2052, Australia 2 Department of Advanced Materials Processing and Analysis Centre, University of Central Florida, FL 32816, USA 3 Rochester Institute of Technology, USA 4 University of Notre Dame, USA A series of ceria nanoparticles were synthesized by using a microemulsion method. The effect of relative concentration of surfactant/water on the size and the surface roughness of ceria nanopar- ticles was examined using transmission electron microscopy (TEM) and atomic force microscopy (AFM) respectively. The investigation confirmed a relationship between the size and the roughness properties of the nanoceria as a function of the water to surfactant ratio. With increasing dilution of the surfactant, the size distribution became narrow such that average particle size decreased linearly as the ratio increased without affecting lower size threshold of particles (∼10 nm). The sur- face roughness, on the other hand was found to increase with increasing water to surfactant ratio implying diluted surfactant would provide rougher surface of ceria nanoparticles. The information can be used to tailor the adhesion properties of nanoceria by optimizing the size distribution as well as surface roughness as a function of water to surfactant ratio. Keywords: Ceria, Nanoparticles, AFM, TEM, Microemulsion, Sol–Gel, Surfactant, Roughness. 1. INTRODUCTION Due to increasing economic and environmental concerns, there is increasing demand to prepare high performance materials such as Thermal Barrier Coatings (TBC) in order to enhance the efficiency of many industrial processes. Popular TBC materials such as yttria-stabilized zirconia (YSZ) are approaching to their performance limits leading to development of alternative materials. 1 Ceramics oxides such as perovskite, heavy atom doped zirconia and ceria based materials are some of the promising materials being developed, which are believed to display higher perfor- mance when compared to commonly used thermal barrier coating materials. 2–4 Due to high versatility such as higher phase stability, thermal properties and lower oxygen dif- fusivity, ceria is one of the most promising high perfor- mance materials. 5–6 Ceria containing materials find wide range of applications including in metallurgy industry to improve oxidative resistance of steel, 6 catalysis, functional ∗ Author to whom correspondence should be addressed. ceramics and as solid electrolyte materials for fuel cells. 7 Most of the properties of the nanosized materials are often found to be different from those of micron-sized particles such as higher surface area, and to depend on size, shape and composition. Therefore, there is increasing emphasis in developing nano-ceria as potential catalytic materials. Recently, sol–gel or microemulsion technology has become a popular technique to prepare nano-phase mate- rials including ceria. 7–12 In sol–gel processing, a polar solvent is added to a mixture of non-polar solution and sur- factant, the surfactant molecules get coordinated with the help of water molecules to form spherical globules (micelles) resulting in synthesis of nanoparticles. Subse- quent densification stages often produce quite uniform microstructure, high packing density with limited flaws. The process conditions such as the nature of the surfac- tant, the relative concentration of reactants and the cal- cination temperature can influence the size of the ceria nanoparticles. 8 For example, different surfactant types and their relative concentration and calcination temperature were shown to influence the particle size distribution. 8 J. Nanosci. Nanotech. 2005, Vol. 5, No. 7 1533-4880/2005/5/1101/007/$17.00+.25 doi:10.1166/jnn.2005.151 1101