Effect of sol–gel modifications on formation and morphology of nanocrystalline lanthanum aluminate S. Naci Koc a, * , Faruk Oksuzomer a , Erdem Yasar b , Selcuk Akturk b , M. Ali Gurkaynak a a Department of Chemical Engineering, Istanbul University, Istanbul, Turkey b Department of Physics, Kirikkale University, Kirikkale, Turkey Received 25 November 2005; received in revised form 4 April 2006; accepted 18 April 2006 Available online 4 May 2006 Abstract LaAlO 3 powders are prepared by sol–gel method. The effect of preparation conditions on morphological properties and crystal formations are investigated. iso-Propanol/tert-butanol and ethyl acetoacetate/ethylene glycol monomethylether are used solvents and complexing agents, respectively. Samples are dried with conventional and freeze-drying methods and calcined between 600 and 1000 8C. TGA, DTA, XRD, SEM and TEM methods are used for characterization. It is observed that freeze-dried sample prepared with tert-butanol has the lowest LaAlO 3 formation temperature and uniform rhombohedral crystals. But conventionally dried sample, prepared with iso-propanol has smallest agglomerates at 1000 8C and does not show clear crystallization temperature in DTA analysis. The XRD peaks of LaAlO 3 crystal are observed at 600 8C for all samples prepared by various sol–gel conditions. # 2006 Elsevier Ltd. All rights reserved. Keywords: A. Nanostructures; B. Sol–gel chemistry; C. X-ray diffraction; D. Microstructure 1. Introduction Lanthanum aluminate has gained great importance in variety of applications in recent years. This material has shown potential for producing high frequency capacitors, microwave dielectrics, catalyst support for high-temperature partial oxidation and dehydrogenation reactions. The single crystal forms of lanthanum aluminate are a promising substrate for high-temperature superconductor films. Moreover, it has also potential application for solid oxide fuel cell (SOFC) electrolyte material when doped with cation such as Sr 2+ and Mg 2+ due to enhanced oxygen ionic conductivity at intermediate temperatures (600–800 8C). For these different applications low/high surface area, uniform and small grain size, chemical homogeneity, low synthesis and sintering temperature are very important parameters [1–6]. Lanthanum aluminate is conventionally synthesized by solid-state reaction using Al 2 O 3 and La 2 O 3 precursors in the temperature range of 1500–1700 8C. In that case, chemical dishomogeneity, high reaction temperature and large grain size are the main disadvantages. Many attempts have been done to lower synthesis temperature using different preparation routes such as co-precipitation, aerosol combustion, in situ polymerization, sol–gel and polycarboxylic acid complexation. Kumar et al. [7] has produced LaAlO 3 by thermal decomposition using hydrated nitrate precursors. www.elsevier.com/locate/matresbu Materials Research Bulletin 41 (2006) 2291–2297 * Corresponding author. Tel.: +90 212 591 24 79; fax: +90 212 473 71 80. E-mail address: nacik@istanbul.edu.tr (S.N. Koc). 0025-5408/$ – see front matter # 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.materresbull.2006.04.025