B-site Y3+ assisted charge compensation strategy to synthesize Eu3+ doped Ruddlesden-Popper Ca2SnO4 perovskite and photoluminescence properties

The rare-earth doped phosphors are widely used in luminous applications. As necessary activators, the involved rare-earth ions are quite low in amount. This may lead to the unsuccessful incorporation or existence of secondary impurity, which, in turn, causes the incorrect interpretations in photoluminescence (PL) origins and mechanisms, e.g. in Eu3+doped Ruddlesden-Popper Ca2SnO4 perovskite. In this work, we adopted a B-site Y3+ assisted charge compensation strategy to dope A-site rare earth Eu3+ cations into Ca2SnO4 in order to obtain the pure-phase red-emission phosphors. The Ca2-xEuxSn1-yYyO4 (x = y = 0.01–0.05) phosphors were synthesized via the one-step solid-state reaction. The careful and systematic XRD measurements reveal that only Eu3+ doping cannot give pure-phase Ca2-xEuxSnO4, while the combination with B-site Y3+ assistance enables achieving pure-phase Ca2-xEuxSn1-yYyO4, which crystallize in an orthorhombic Pbam structure. The STEM-EDX and XPS characterizations indicate the uniform distribution of dopants in the matrix and B-site Y3+ plays a charge compensation role and assists the A-site Eu3+ doping. The charge transfer state (CTS) presenting the energy transfer from matrix to dopants (O2--Eu3+) in excitation spectra was observed with the center at around 275 nm. This excitation wavelength can give the strongest emission signals, i.e. the overall warm-reddish emission. The comprehensive structure and PL/FT-IR/UV spectroscopy analyses indicate that Eu3+ ions substitute for Ca2+ ions at a low symmetric position, and the electric-dipole transition (5D0→7F2) is dominant, giving rise to the stronger emission at 617 nm. The optimal PL emission is achieved at doping level x = 0.03, beyond which the concentration quenching occurs, with an origin of electric dipole-dipole interaction of Eu3+ responsible.