Pressureless sintering of LRH nanoplates on amorphous alumina for near-infrared GAP:Mn4+ transparent ceramic film

We developed a pressureless sintering method to prepare GdAlO3: Mn (GAP: Mn) transparent ceramic films, which were prepared by spin coating layered rare earth hydroxide (LRH) on amorphous alumina substrate and sintering at 1550 oC for 2 hours. Through the interface reaction, the Al2O3 reacted with Gd2O3 to form mesophase Gd4Al2O9 below 1550oC. However, the final products are GdAlO3 at 1550 oC. The GAP: Mn4+ film exhibits a high transmittance of about 90%. Under UV excitation at 310 nm, the ceramic film outputs deep red and NIR emissions, which are both arising from the 2Eg-4A2g transition of Mn4+. Due to the electron traps arising from unequal valence substitution, the ceramic film exhibits a negative thermal quenching phenomenon. The ceramic film has a good luminescence thermal stability, because its emission intensity at 150 oC maintains over 72% that at room temperature. This work may pave a new way to fabricate transparent ceramics using layered rare earth hydroxides.