Cross relaxation in CaTiO3 and LaAlO3 perovskite nanocrystals doped with Ho3+ ions

LaAlO3: Ho3+(0.5-10%) and CaTiO3: Ho3+ (0.1-2%) nanosized perovskites were prepared with the Pechini and sol-gel method, respectively. The spectroscopic properties of CaTiO3: Ho3+ were investigated for the first time. The cross relaxation energy transfer processes were determined as a function of Ho3+ concentration, by examination of the two strongest transitions observed in the visible region arising from 5S2 and 5F5 multiplets. The cross relaxation processes for the investigated Ho3+ levels were described. It was found that the clustering processes for CaTiO3 is so strong, that increase of dopant concentration weakly influence the cross relaxation processes, while in LaAlO3, where dopants are located randomly in the crystal lattice, clear monotonic dependence is observed.