Yttrium aluminum garnet, Y 3 Al 5 O 12 , YAG monoliths with well-defined macropores have been prepared from ionic precursors using the sol-gel method accompanied by phase separation. The addition of propylene oxide to the starting solution controls the gelation, while the addition of poly ethylene oxide induces the phase separation. Polymerization-induced phase separation and gelation concur by an appropriate selection of the starting composition, which allows the production of bicontinuous macroporous nanocomposite gels in large dimensions Ĭ10j10j10 mm 3 . During heat treatment at 800c C, the monolithic nanocomposite gels crystallize into YAG without the formation of any intermediate phases or the precipitation of impurity phases, indicating higher homogeneity of cation distribution in the dried gels. The macroporous YAG network was maintained even after heat treatment at 1000c C for 10 h.