The Preparation Of High Performance Lanthanum Aluminate Powder

As a novel type of rare earth functional materials, lanthanum aluminate has widely been used in the fields of electronic devices, catalysts, high temperature fuel cells, advanced ceramics, sewage treatment, and substrate materials. Lanthanum aluminate crystal possesses excellent features and great potential application. Thus, it is necessary to develop a simple, economical technique to prepare high-purity and ultrafine lanthanum aluminate powders. Therefore, the preparation research on ultrafine lanthanum aluminate is very significant.In the present work, lanthanum aluminate powder was synthesized by several process routes with different starting materials: (i) boehmite and lanthanum oxalate; (ii) boehmite and lanthanum acetate; (iii) aluminium isopropoxide and lanthanum oxalate; (iv) aluminium isopropoxide and lanthanum acetate; (v) lanthanum, isopropanol and aluminium tri-chlorinate. In the case of (i) or (ii), lanthanum aluminate powders were obtained via high temperature solid state reaction from the stating materials, after being ground and mixed with additive (AlF₃, AlCl3₃) and dispersion medium. By means of biomicroscopy, TG-DTA, SEM and XRD, the thermal decomposition process of the precursor and the effects of dispersion medium, temperature and additives on the synthesis of lanthanum aluminate were investigated. In the case of (iii) or (iv), lanthanum aluminate powder was prepared by gel-solid state reaction. The drying process of gel and the thermal decomposition process of precursor, the effect of temperature and additives on the phase transformation and the particle morphology were investigated. In the case of (v), the synthesis of lanthanum alkoxide and aluminium alkoxide.Results showed that single phase lanthanum aluminate powder was obtained by holding for 3h at 1200℃, with boehmite and lanthanum oxalate as starting materials, with 2wt%AlCl3₃ or 3wt%AlF₃ as additive. Regular and spherical particles were obtained with AlCl3₃ as additive, and primary particle size is about 300nm. The secondary particle size is 1μm and grain well developed with AlF₃ as additive. Sample was prepared by gel-solid phase, with aluminium isopropoxide and lanthanum acetate as starting materials, According to TG-DTA curve synthesis temperature of lanthanum aluminate was 900℃, coincide with the XRD. Precursor was made with lanthanum, isopropanol and aluminium tri-chlorinate as starting materials, by hydrolysising and drying, single phase lanthanum aluminate powder wae obtained after calcining at 1200℃for 3h. The optimal preparation technique of lanthanum aluminate powder is the solid state process with boehmite and lanthanum oxalate as the starting materials, 2wt% AlCl3₃ or 3wt% AlF₃ as additive, via solid state mixed-grinding, single phase lanthanum aluminate powder wae obtained after calcining at 1200℃for 3h.