A promising molten silicate resistant material: Rare-earth oxy-apatite RE9.33(SiO4)6O2 (RE = Gd, Nd or La)

In this work we reported a new class of rare earth oxy-apatite, RE9.33(SiO4)6O2, with superior molten silicate resistant capability which shows promising application for thermal barrier coatings (TBCs). Three RE elements with different ion radius, i.e., Gd, Nd and La, were selected to prepare RE9.33(SiO4)6O2 bulk using co-precipitation and pressless-sintering. After 8-h CMAS attack at 1300 °C, the specimens exhibited a dense, continuous reprecipitated layer at RE-apatite/CMAS interface, which is predominantly controlled by a dissolution-reprecipitation mechanism distinguishing from the sacrificial material which is usually with reaction layer being formed. With an increase of ion radius, apatite is easier to crystallize in the melt.