Near-infrared luminescence of manganate(V)-doped phosphates and vanadates

Manganese(V) is stabilized in various phosphate and vanadate lattices with apatite and spodiosite structure on quasi-tetrahedral sites. At all temperatures between 10 and 298 K the luminescence spectra consist of sharp lines in the near infrared, assigned to 1E → 3A2 (Td). The observed splitting ΔE between the two low-symmetry orbital components of the emitting state 1E(Td) is correlated with structural distortion data of the (PO4)3- and (VO4)3- tetrahedra in the host. Luminescence lifetimes of Mn5+ in five different compounds vary between 300 and 700 μs at 10 K. At room-temperature lifetimes are reduced by factors of 1.4 to 11, depending on the host lattices.