The sinterability and microstructural evolution of mixed-metal Y3Al5-xCrxO12 (YACRG), Y3Al5-xMnxO12 (YAMNG), Y3Al5-xNixO12 (YANIG), Y3Al5-xCoxO12 (YACOG), Y3Al5-xCuxO12 (YACUG) and Y3Fe5-xCoxO12 (YICOG) (0 <= x <= 2.75) garnets powders, synthesized by an aqueous sol-gel process, were investigated. The synthesized samples were characterized by infrared spectroscopy (IR) and X-ray diffraction (XRD). Scanning electron microscopy (SEM) was used to study the morphology and microstructure of the synthesized samples. It was demonstrated, for the first time to the best our knowledge that the formation of YACRG, YAMNG, YANIG and YACOG garnets proceeds only within narrow substitutional range. Considerably less substitutional limit was observed for the YACUG garnet. On the other hand, the formation of monophasic YICOG garnet did not proceed at the same synthesis conditions. Furthermore, the limitary radius of garnet structure compounds was calculated. It was found that the linear dependence of the radius of M3+ cations distributed among tetrahedral and octahedral sites versus value of the limitary radius of garnet structure compounds exists. (C) 2012 Elsevier B.V. All rights reserved.