In situ synthesis of composite MTiO3-Al2O3 coatings via laser zone melting

Laser zone melting was employed in this work to prepare MTiO3 based coatings over commercial, polycrystalline Al2O3 substrates, using the corresponding mixtures of powdered alkaline earth carbonates and TiO2 as starting materials. In situ synthesis of the series M=Ca, Sr, Ba was studied using a CO2 laser as the heating source, emitting at 10.6 mu m, following substrate preheating to a temperature of 750 degrees C and sample displacement speed of 500 mm h(-1). Microstructure (SEM) and phase composition (XRD) demonstrated in situ formation of crystalline MTiO3 perovskite (M=Ca, Sr), MAl2O4 (M=Ca), MAl12O19 magnetoplumbite type (M=Sr) and MAl14O22 beta-alumina type (M=Ba) phases. Substantial interaction with the substrate resulted in stable, 50-150 mu m thick, composite coatings. (c) 2007 Elsevier Masson SAS. All rights reserved.