Mechanochemical Synthesis of ZrTiO₄ Precursor from Inhomogeneous Mixed Gels

Abstract

Effects of vibration ball-milling of a powdered mixture of two gels, prepared from mixing ZrO2 andTiO2 sols, on crystallization processes during heating are studied in order to elucidate enhanced mechanochemical reactions with the aid of hydroxyl groups. TiO2 (anatase) and ZrO2 (tetragonal) crystallized at 698 K and 712 K, respectively, when heating non-milled gel mixture at 10 K min1 in air. Few reactions between the two phases were detected below 1023 K. After vibro-milling a powdered gel mixture at room temperature for 3 to 30 h, ZrTiO4 (orthorhombic) crystallized directly from non-crystalline precursors on heating to 1023 K. The fraction of crystallizedZrTi04, determined by Raman spectroscopy, increased linearly with increasing the index of micro-homogeneity for non-heated gels. We suggest that short-range ordering of ZrTiO4 rather than crystallization of individual oxides occurs through the non-thermal atomic movement between different metallic species under mechanical stress.

X-ray Diffraction and X-ray Absorption Spectroscopy Studies of Sol−Gel-Processed Zirconium Titanates

“…Therefore, alternative approaches to the preparation of high-quality powders have been explored. The routes investigated include a polymeric precursor made from titanium butoxide and zirconium oxychloride octahydrate, 7,8 coprecipitation from aqueous solution, [9][10][11] trolytic deposition, 12 mechanochemical synthesis, 13 conventional alkoxide sol-gel methods, 3,14 a nonalkoxide sol-gel procedure in which zirconium acetylacetonate was mixed with acetic-acid-modified titanium isopropoxide, 15 and nonhydrolytic sol-gel routes. 16 In this paper, four procedures for the preparation of ZrTiO 4 are compared: a conventional alkoxide sol-gel route, an acetic-acid-modified sol-gel route based on that previously reported for lead zirconium titanate (PZT), 17,18 a nonhydrolytic sol-gel method, and a mixed oxide route.…”

“…Therefore, alternative approaches to the preparation of high-quality powders have been explored. The routes investigated include a polymeric precursor made from titanium butoxide and zirconium oxychloride octahydrate, , coprecipitation from aqueous solution, − electrolytic deposition, mechanochemical synthesis, conventional alkoxide sol−gel methods, , a nonalkoxide sol−gel procedure in which zirconium acetylacetonate was mixed with acetic-acid-modified titanium isopropoxide, and nonhydrolytic sol−gel routes …”

Extremely Low Temperature Crystallization in the A2M3O12 Family of Negative Thermal Expansion Materials

“…For example, synthesis of ZrTiO 4 requires the use of chelating agents to slow down the reaction of the titanium precursor. [26] An elegant alternative to this is the use of a non-hydrolytic sol-gel (NHSG) method. [20][21][22]27,28] In this approach, metal halides or alkoxides are reacted with secondary or tertiary ethers in a non-aqueous environment.…”

Novel Materials through Non-Hydrolytic Sol-Gel Processing: Negative Thermal Expansion Oxides and Beyond

“…A limitation of aqueous sol-gel processes arises for mixed metal oxides where individual components show very different hydrolysis rates (e.g., ZrTiO 4 ) [ 30 ]. In such cases, complexing agents are required to slow down the hydrolysis of the more reactive precursor.…”