Structural properties of yttrium aluminosilicates microspheres

Aluminosilicate microspheres with and without yttrium, obtained by combined sol–gel and spray-drying method, were investigated as materials with great potential in biomedical applications. Electron microscopy (SEM and TEM) analyses were used to examine the morphology of the as-prepared samples. The spray dried particles showed a spherical shape, but some distortions of their surfaces due to the particles collision in the spray cylinder are present. The X-ray diffraction patterns indicate an amorphous structure of as-prepared samples and the development of small nanocrystals in the yttrium containing samples. The local structure and its changes induced by aluminum substitution with yttrium in the microspheres network have been investigated by means of 29Si and 27Al MAS NMR. The network of the sample containing yttrium has been found to be more depolymerized than that of the sample without yttrium.

Research highlights► Low temperature synthesis of aluminosilicate microspheres using combined sol–gel and spray-drying methods. ► Yttrium substitution for aluminum affects to a less extent the distribution of aluminum sites, in agreement with the fact that yttrium is mainly disposed in yttrium rich nanocrystals. ► At the same time the development of silica rich region with much uniform oxygen distribution around Q4 units is favored.