ELSEVJER August 1997 Materials Letters 32 (1997) 203-208 Low temperature U.S. Hareesh, Asha sintering of seeded aluminium titanate precursor gels K. Vasudevan, P. Mukundan, A.D. Damodaran, K.G.K. Warrier * zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQ Structural Ceramics Unit, Regional Research Laboratory (CSIR), Thiruuananthapuram 695019, Kerala, India Received 4 March 1997; revised 14 April 1997; accepted 5 May 1997 zyxwvutsrqponmlkjihgfedcbaZYXW Abstract Aluminium titanate has been prepared by thermal decomposition of a precursor gel formed by the controlled flocculation of a homogeneous mixture of boehmite and titanium isopropoxide ~01s. The effect of aluminium titanate seed nuclei, with average size less than 0.25 mm, on the phase formation, densification and microstructure development is reported. The results indicate enhanced densification kinetics for the seeded precursor. Such gels after calcination at 1000°C for 2 h were sintered to densities of - 96% at 1300°C for 30 min. Nearly complete formation of the aluminium titanate phase was achieved under the present experimental conditions. A simultaneous densification and phase formation from a liquid phase assisted titania rich precursor is suggested. On the other hand the unseeded gels could achieve only < 85% densification under identical conditions. 0 1997 Elsevier Science B.V. Keywords: Low temperature sintering; Aluminium titanate: Precursor gel 1. Introduction which help reducing the microcracks [4-61. Further, Aluminium titanate, a low thermal expansion ce- aluminium titanate decomposes partially to its con- ramic with properties of high melting point, high stituent oxides in the temperature range 800-1250°C thermal shock resistance and very low thermal con- cooling after densification, which is also reported to ductivity is reported to be quite suitable for high be grain size dependent [7]. Hence careful control of temperature applications such as heat engine ceram- the processing parameters is a prerequisite for ob- its [1,2]. This ceramic, however, has been restricted taining sintered alurninium titanate with acceptable in its use as a structural material due to anisotropic mechanical and thermal properties. thermal expansion and attendant formation of micro- AIurninium titanate is usually synthesised by heat cracks which considerably reduce its mechanical treatment of an intimate mixture of alumina and strength [3]. Usually aluminium titanate is stabilised titania above 1450°C. Under these conditions the by introducing additives like MgO, Fe,O, and SiO, sintered ceramic undergoes enhanced grain growth resulting in microcracks [S]. Sol gel techniques were successful bringing down the temperature of the * Corresponding author. Tel.: +91-471-490674; fax: +91-471. formation as well as the sintered grain sizes in 491712; e-mail: warrier@csrrltrd.ren.nic.in. aluminium titanate [9]. Recently Messing et al. iden- 00167-577X/97/$17.00 Q 1997 Elsevier Science B.V. All rights reserved. PII SO167-577X(97)00153-5