Upconversion photoluminescence and dielectric properties in Er3+ and Yb3+ co-doped Sr4La2Ti4Nb6O30

Filled tetragonal tungsten bronze (TTB) structure Sr 4 La 2 Ti 4 Nb 6 O 30 co-doped by Er 3+ and Yb 3+ (SLTN: x Er 3+ – y Yb 3+ ) ceramics with different x and y were synthesized, and their crystal structure, upconversion photoluminescence (UC-PL), and dielectric permittivity were investigated for the first time. Under 980   nm infrared (IR) excitation, bright single-band UC green (515–570   nm) emission was observed for SLTN: x Er 3+ – y Yb 3+ ( x =0.05, y =0), however, featured two-bands UC emission (515–570   nm and 640–690   nm) was confirmed for all SLTN: x Er 3+ – y Yb 3+ ( x =0.05, y ≠0) samples. Two-photon energy transfer process was proved through pumping laser power dependence of emission intensity measurement. It is believed that energy back transfer (EBT) process should be mainly responsible for the two-bands UC emission. In addition, the dielectric properties were also discussed for SLTN: x Er 3+ – y Yb 3+ system.