Color‐Tunable Up‐Conversion Emission and Infrared Photoluminescence and Dielectric Relaxation of Er 3+ / Yb 3+ Co‐Doped Bi 2 Ti 2 O 7 Pyrochlore Thin Films

The color‐tunable up‐conversion ( UC ) emission and infrared photoluminescence and dielectric relaxation of Er 3+ / Yb 3+ co‐doped Bi 2 Ti 2 O 7 pyrochlore thin films prepared by a chemical solution deposition method have been investigated. The pyrochlore phase structure of Bi 2 Ti 2 O 7 can be stabilized by Er 3+ / Yb 3+ co‐doping. Intense color‐tunable UC emission and infrared photoluminescence can be detected on the thin films excited by a 980 nm diode laser. Two UC emission bands centered at 548 and 660 nm in the spectra can be assigned to 2 H 11/2 , 4 S 3/2 → 4 I 15/2 and 4 F 9/2 → 4 I 15/2 transitions of Er 3+ ions, respectively. A Stokes infrared emission centered at 1530 nm is due to 4 I 13/2 → 4 I 15/2 transition of Er 3+ ions. The dependence of UC emission intensity on pumping power indicates that the UC emission of the thin films is a two‐photon process. The thin films also exhibit a relatively high dielectric constant and a low dissipation factor as well as a good bias voltage stability. Temperature‐ and frequency‐dependent dielectric relaxation has been confirmed. This study suggests that Er 3+ / Yb 3+ co‐doped Bi 2 Ti 2 O 7 thin films can be applied to new multifunctional photoluminescence dielectric thin‐film devices.