Journal of Optoelectronics and Advanced Materials Vol. 5, No. 5, 2003, p. 1411 - 14 16 Al 2 TiO 5 -BASED CERAMICS OBTAINED BY HYDROTHERMAL PROCESS M. Zaharescu * , M. Crisan, M. Preda a , V. Fruth, S. Preda Institute of Physical Chemistry “I. G. Murgulescu”, 202 Splaiul Independentei, 060022 Bucharest 6, Romania a Politehnica University of Bucharest, 1-7 Ghe. Polizu, 011061 Bucharest 1, Romania Aluminum titanate is a very interesting compound due to some special properties as: high refractivity, low thermal conductivity and low thermal expansion coefficient, that confers to the aluminum titanate based ceramics high resistance to the thermal shock. Eutectoid decomposition in the initial oxides and low mechanical strength limit the well-known properties of aluminum titanate desired in several applications. In order to minimize these limitations new synthesis routes and additives were studied. In the present work the phase formation and sintering behavior of aluminum titanate powders obtained by hydrothermal method is studied using DTA/TG, XRD, IR and ceramic properties determination (density, absorption, porosity) as investigation methods. (Received July 28, 2003; accepted August 28, 2003) Keywords: Sol-gel hydrothermal method, Aluminum titanate, Precursor powders 1. Introduction Aluminum titanate ceramics were heretofore known as an important high-temperature employable product, as articles for high-temperature portions of an automotive engine, parts for high- temperature portions in electric and electronic devices, parts in nuclear reactors such as shielding materials for use in nuclear fusion reactors, tools for a melting furnace of non-ferrous alloys and ferroalloys or articles for measuring the temperature of molten metal or glass in a furnace [1]. Aluminum titanate, named also tialite, is used in a variety of high-temperature branches for its properties. The thermal expansion coefficient with values ranging between 0.2-1×10 -6 K -1 [2] is comparable with the fused silica expansion coefficient (10 times higher), but the monocrystals present an extreme anisotropy, with values ranging between (+3)→(-19)×10 -7 K -1 [3], causing the occurrence of microcracking phenomena at the grain boundary. Tialite have also an excellent thermal shock resistance, low Young modulus, high refractivity temperature (melting point ~ 1850 °C) [4] and is non- wetted and does not react with many molten non-ferrous metals and alloys. The common use of this material for high temperature applications is limited by the low fracture strength, caused by the microcracking phenomena and the thermodynamic decomposition over a given range of temperature. The phase equilibrium diagram shows that 1200 °C is the temperature below tialite becomes thermodynamically unstable [5]. As the correlation between the grain size and microcracking is proved a grain size distribution and a small size of particles are desirable for a good sintering behavior and a limited development of the microcracks [5]. There are many studies for the improvement of overall properties, starting from different synthesis methods to the introduction of additives and obtaining of aluminum titanate based ceramic * Corresponding author: mzaharescu@chimfiz.icf.ro