Yb3+ quenching effects in co-doped polycrystalline BaTiO3:Er3+, Yb3+

Luminescent properties of single and co-doped samples of sol-gel polycrystalline BaTiO3 with trivalent Er3+ and Yb3+ ions are reported. Under 520 nm pumping, visible radiative emission from 2H7/2, 4S3/2 → 4I15/2, and 4F9/2 → 4I15/2; and near infrared emission from 4S3/2 → 4I13/2, 4I11/2 → 4I15/2 and 4I13/2 → 4I15/2 of Er3+ and from 2F5/2 → 2F7/2 of Yb3+ ions were measured. For single Er3+ doped samples, concentration quenching was observed from the 4S3/2 state, whereas emissions in the 1.0 and 1.5 μm regions increase with concentration due to the cross-relaxation mechanism 4S3/2 + 4I15/2 → 4I9/2 + 4I13/2. Upon addition of Yb3+ ions quenching is enhanced, as corroborated by the luminescence decay time curves and emission spectra. This is so because an additional non-radiative energy transfer process from the thermally coupled states (2H11/2, 4S3/2) of Er3+ to the 2F7/2 state of Yb3+ takes place.