Electric-field-induced composite color centers formation and Yb ions valence state change in spark plasma sintered Yb:YAG transparent ceramics

Abstract Transparent Yb:YAG ceramics with submicron-scale grains were fabricated through the spark-plasma-sintering of co-precipitated Yb:YAG powders without the use of any additives. Yb valence state shift and composite color center formation were investigated by visible range absorption spectra、Emission spectra and Electron Paramagnetic Resonance (EPR) measurements. The underlying mechanisms by which an applied field influences the valence state transition and composite color center formation are discussed in detail. Absorption spectra measurements of Yb:YAG ceramics consolidated by SPS at 1100–1300 °C revealed absorption bands located at 380, 487, 524, 634, 646, and 654 nm. EPR characterization and photoluminescence spectrum confirmed the presence of a Yb 2+ ion population with the 4f 13 ground state electronic configuration by the 589 nm luminescence under 354 nm excitation, formed by the Yb 3+ ion capturing an electron to form Yb 2+ -F + composite color centers. It was determined that both the shift in Yb valence state and the formation of composite color centers were caused by the electric field employed to conduct the sintering process.