Preparation of Al2TiO5-ZrO2 Mixed Powders via Sol-Gel Process

Sol-gel routes in the ternary system Al2O3-TiO5-ZrO2 were investigated to prepare Al2TiO5-ZrO2 mixed powders. The preparation of ZrTiO4 and Al2TiO5 was studied before going on with the ternary system. Zirconium titanate precursor gels were prepared from Ti(OPri)(4) and Zr(OPrn)(4) mixtures. The crystallization of ZrTiO4 develops at T < 700 degrees C. Al2TiO5 was prepared by different ways, using mixtures of Al(OBuS)(2)(C6H9O3) with Ti(OPri)(4) (i), or with acetic acid addition (ii). Route (i) leads to a separate crystallization of TiO2 and alpha-Al2O3, with subsequent formation of beta-Al2TiO5 at T approximate to 1360 degrees C. Although the pseudobrookite beta-Al2TiO5 is thermodynamically unstable below 1280 degrees C, route (ii) leads to the crystallization of metastable beta-Al2TiO5 at T approximate to 800 degrees C. At increasing temperature, beta-Al2TiO5 decomposes into TiO2 and alpha-Al2O3, then the two compounds react to form stable beta-Al2TiO5. For the ternary system, all the preparation routes which were studied lead to ZrTiO4 and alpha-Al2O3 with subsequent reaction (at T approximate to 1500 degrees C) to give beta-Al2TiO5 and ZrO2.