Gradient, porous alumina ceramics were prepared with the characteristics of microsized tabular alpha-Al2O3 grains grown on a surface with a fine interlocking feature. The samples were formed by spin-coating diphasic aluminosilicate sol on porous alumina substrates. The sol consisted of nano-sized pseudo-boehmite (AlOOH) and hydrolyzed tetraethyl orthosilicate [Si(OC2H5)(4)]. After drying and sintering at 1150 degrees-1450 degrees C, the crystallographic and chemical properties of the porous structures were investigated by analytical electron microscopy. The results show that the formation of tabular alpha-Al2O3 grains is controlled by the dissolution of fine Al2O3 in the diphasic material at the interface. The nucleation and growth of tabular alpha-Al2O3 grains proceeds heterogeneously at the Al2O3/glass interface by ripening nano-sized Al2O3 particles.