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PACS 78.55.Hx, 81.05.Je, 81.20.Fw Powders of yttria-alumina materials YAlO 3 (YAP) and Y 3 Al 5 O 12 (YAG) have been prepared from commercially-available preformed sols, and the products were compared with those from preformed solnitrate, nitrate-citric acid and alkoxide methods. The preformed sol route offers an alternative cheap and rapid method, and different sizes of the nanometre-scale precursors are available. Characterization was carried out by SEM, XRD, TG-DTG-DTA and FTIR-DRIFTS. On doping with Er 3+ , the maximum intensity of green emission was found for a dopant ion concentration of 1.0-1.2 mol%, with cross-relaxation to depopulate 2 H 11/2 / 4 S 3/2 becoming more important at higher dopant ion concentrations. A memory effect of the precursor sol upon the luminescence intensity of the product was able to distinguish precursors from two different suppliers. Demonstrations are given of the use of site-selective luminescence spectra in monitoring the purity of the yttria-alumina products. catalytic applications [22], partly because they are widely available and much cheaper than alkoxides. Preformed sols are stable mixtures of dispersed particles within a given size range, which by contrast to the conventional hydrolysis-polymerization sol-gel reactions of alkoxides, enable the sol and gel processes to be isolated and performed in two steps. This is attractive because it offers potential control over the particle size, crystallinity and microstructure of the product. The preformed sol route has other advantages that different-size precursors are readily available in aqueous solutions, employed herein, or as dispersed powders. The alumina sols consist of porous aggregates of rod-or platelet-boehmite (γ-AlO.OH.nH 2 O) crystallites [22]. It has been envisaged [22] that nanometer-scale mixing of preformed sols of widely-different sizes, such as large alumina and small silica particles, results in isolated large particles dispersed in a sea of smaller particles.The goal of the present study was to utilize preformed sols in the preparation of YAP and YAG. These materials were doped with the lanthanide ion Er 3+ , which has intense, well-characterized emission properties. In addition, several areas were investigated concerning the resulting luminescence properties of the doped YAP and YAG materials: the concentration-intensity dependence of the luminescence, the possible occurrence of precursor memory effects, and the site-selective resolution of product materials. A preliminary report of some areas of the present study was made at the IUPAC International Congress on Analytical Sciences [23].

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