Introduction In 1989 Kuznicki synthesized new titanium based mate- rials [1]. Chapman in 1990 synthesised microporous titanosilicate used as molecular sieves [2]. The ETS-10 is a newly formed titano-silicate the structure of which was resolved thanks to the XRD, EDS, HREM and mass NMR [3]. The structure contains TiO 6 octahedra, two oxygen atoms being shared by neighboring TiO 6 units forming a Ti–O–Ti chain, while the other four ox- ygen atoms are shared with neighboring tetrahedral SiO 4 groups [3, 4]. A set of periodically placed chains develops that way in an orthogonal direction. The super- imposition of layer of this type gives rise to a tridimen- sional structure of 12 membered ring channels. Only few zeolitic structures have such an open structure, the more important ones being zeolite Y (FAU) and zeo- lite Beta (BEA). Each titanium atom in this structure is associated with two negative charges that are neutral- ized by cations not being part of the structure. The den- sity of cations is roughly similar to that of a zeolite with Si/Al=2.5. Due to the long interconnecting pores in the structure and the high density of the extraframework cations, the ETS-10 is a potentially good catalyst. In ad- dition, aluminium can be substituted at tetrahedral posi- tions replacing silicon and hence Broensted acid sites can be introducted [5, 6]. In ETS-10, the disposition of the layers composed of Ti–O–Ti chains in an orthogonal way is not regular leading to defects in the structure. The disorder can be modelled by the combination of two polymorphic structures that are due to different se- quences. The polymorph A corresponds to a sequence ABCD and has a monoclinic symmetry with C2/c space group, while the other corresponds to a sequence ABAB and has a tetragonal symmetry with space group P41 or P43 [7]. Eldewik et al. have investigated the incorpora- tion of Co 2+ ions into ETS-10 [8]. Neither the physico- chemical nor the catalytic properties of ETS-10 are well characterized. Anyway it is not clear how they could be influenced by the disorder. Anderson et al. used a com- bination of atomic force microscopy, high-resolution electron microscopy and modelling to elucidate the de- tails of the mechanism of crystal growth in framework of ETS-10 and other materials [9]. Kim et al. reported studies on the crystallization of ETS-10 using various compositional systems in presence of organics and in the absence of seeds [10, 11]. Picquart et al. studied the chemical-physical behaviour of sol–gel zirconia [12]. Naik et al. synthesized a sodium zirconium phosphate, potential ceramic matrix for fixation of high level nu- clear waste [13]. Experimental The synthesis procedure for ETS-10 molecular sieves is identical to that proposed by Pavel et al. [14]. Two batches are separately prepared, the one being alkaline and the other acidic. For the alkaline batch the ingredi- ents are added in the following order: sodium silicate (Merck; 8% Na 2 O, 27% SiO 2 , 65% H 2 O), sodium hy- droxide (Carlo Erba; 50 mass%) and potassium fluoride (Merck; 40 mass%). For acidic batch the components are added in the following order: distilled water, hydro- chloric acid (Carlo Erba; 37 mass%), titanium tetrachlo- ride (Merck; 50 mass%) and zirconium tetrachloride in 1388–6150/$20.00 Akadémiai Kiadó, Budapest, Hungary © 2005 Akadémiai Kiadó, Budapest Springer, Dordrecht, The Netherlands Journal of Thermal Analysis and Calorimetry, Vol. 80 (2005) 585–590 INFLUENCE OF ZIRCONIUM ON THE CRYSTALLIZATION OF ETS-10 MOLECULAR SIEVE D. Vuono 1* , C. C. Pavel 2 , P. De Luca 1 , J. B. Nagy 3 and A. Nastro 1 1 Dipartimento di Pianificazione Territoriale, University of Calabria, via P. Bucci, C.A.P. 87036, Arcavacata di Rende (CS), Italy 2 Department of Chemical Technology and Materials Chemistry, Faculty of Chemistry, ‘Al. I. Cuza’ University of Iasi, Bd. Carol I, 6600 Iasi, Romania 3 Laboratoire de R.M.N., Facultés Universitaires Notre-Dame de la Paix, 5000 Namur, Belgium The ETS-10 is a newly formed titano-silicate the structure of which was resolved thanks to the XRD, EDS, HREM and mass NMR. The ETS-10 is a potentially good catalyst. The aim of this research is to study the physicochemical properties of ET(Zr)S-10 ob- tained from a gel containing different amounts of Zr. The analyses used are XRD, thermal analysis (TG-DSC), SEM, and 29 Si NMR. Keywords: DSC, ETS-10, initial gels, TG, zirconium * Author for correspondence: danyvuono@yahoo.it