Mn²⁺ activated red long persistent phosphors in BaMg₂Si₂O₇

Novel red long persistent phosphors of BaMg₂Si₂O₇:Mn²⁺, Eu²⁺, Dy³⁺ have been synthesized at high temperature and weak reductive atmosphere. There are a deep blue emission with peak wavelength of 400 nm and a broader emission band centered at 680 nm when excited by 340 nm. The broad emission band is attributed to the spin-forbidden transitions of the d-orbital electrons associated with the Mn²⁺ ions (⁴T₁(⁴G)-⁶A₁(⁶S)). The excitation and emission spectra of the samples with different dopants and doping concentrations show that the Mn²⁺ emission is dominantly due to the persistent energy transfer from Eu²⁺. Red long persistent phosphors have been observed in the system for over 2 h.