Effect of maltose for the crystallization of tetragonal zirconia Hai-Yang Zhu, Bin Liu, Ming-Min Shen, Yan Kong, Xi Hong, Yu-Hai Hu, Wei-Ping Ding, Lin Dong * , Yi Chen Key Lab of Mesoscopic Chemistry and Jiangsu Provincial Lab for Nanotechnology, Department of Chemistry, Nanjing University, Nanjing 210093, China Received 7 October 2003; accepted 14 May 2004 Available online 2 July 2004 Abstract A new method was used to prepare the tetragonal zirconia and high temperature X-ray powder diffraction (XRD) and thermo gravimetry and differential scanning calorimetry (TG – DSC) were employed to study the process of the formation and variation of crystal zirconia. The high temperature XRD results showed that [Nature 258 (1975) 703] during the formation of zirconia from zirconium hydroxide, the addition of maltose favored the phase transformation of zirconia from amorphous to tetragonal as the calcination temperature rises (from about 400 to 550 jC), and then monoclinic zirconia gradually formed as the temperature increases (from about 550 to 846 jC), [Appl. Catal. 71 (1991) 363] tetragonal zirconia would partly transform into monoclinic one during the annealing, and which implies that the suitable calcinations temperature for the preparation of tetragonal zirconia should be controlled lower than 550 jC. In addition, it is suggested that the combination of high temperature XRD and TG – DSC is a powerful tool to approach the process of the formation of solid materials. D 2004 Elsevier B.V. All rights reserved. Keywords: Tetragonal zirconia; TG– DSC; High-temperature XRD 1. Introduction As known to all, zirconia has three stable crystal struc- tures depending on temperature (T): monoclinic at T < 1170 jC, tetragonal at 1170 < T < 2370 jC and cubic at T >2370 jC. The mechanical properties of zirconia-based ceramic materials are known to be a function of phase structure and composition [1]. In recent years, a great many interests have been paid on the study of the zirconia as a support in catalysis, and this is because of the fact that zirconia has several useful properties of favoring its application in this field [2]. Among the physical properties that make it a useful support under harsh conditions are its high melting point of 2370 jC, low thermal conductivity, and high corrosion resistance. Chem- ically, zirconia is an amphoteric support that is similar to alumina with oxidizing as well as reducing capabilities [3]. It can be made into a very strong acid by sulphating zirconium hydroxide followed by calcinations [4]. Sulph- ated zirconia is active in the isomerization of linear to branched hydrocarbons. Various reactions such as hydro- desulphurization [5], methanol synthesis [6,7], and the Fischer-Tropsch reaction to give higher hydrocarbons [8,9] were reported to show higher activity and selectivity with zirconia than with conventional supports. However, zirconia exhibits polymorphic forms in the general purchased pro- duction (a mixture of monoclinic, tetragonal, and cubic phases), such as the zirconia produced by Toray Ltd and Tosoh Co., Japan. Generally, the monoclinic phase is thermodynamically more stable at room temperature. And it was well established that, due to the difference of the surface acid site on monoclinic zirconia and tetragonal zirconia, the activity and the selectivity of those catalysts supported on monoclinic zirconia clearly inferior to that of those catalysts on tetragonal and amorphous zirconia [10– 14]. Therefore, more attention has been paid to the prepa- ration of pure tetragonal zirconia in recent years, and it has been reported that tetragonal zirconia can be stabilized by introducing some metal cations, e.g. V 5+ [15], Mo 6+ [16], Y 3+ [17, 18] and Na + [19]. As known to all, the properties of tetragonal zirconia modified by other metal ions should be different in the selectivity of the catalysts from those of 0167-577X/$ - see front matter D 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.matlet.2004.05.050 * Corresponding author. Laboratory of Mesoscopic Materials Science, Chemistry and Chemical Engineering, Nanjing University, Nanjing 210093, China. Fax: +86-25-3317761. E-mail addresses: donglin@nju.edu.cn, chem718@nju.edu.cn (L. Dong). www.elsevier.com/locate/matlet Materials Letters 58 (2004) 3107– 3110