This paper deals with an original method for the preparation of ferrit
es with the garnet structure by coprecipitation. The different transfo
rmations of the coprecipitated hydroxide during heat treatment are stu
died and reported. YIG crystallization from amorphous oxide is signifi
cantly dependent of some parameters. However, pure homogeneous materia
ls can be obtained at low temperature (800-850 degrees C) for Al subst
ituted YIG Y3AlxFe(5-x)O-12 with 0.5 less than or equal to x less than
or equal to 1.