Green Up‐Conversion Photoluminescence and Dielectric Relaxation of Ho 3+ / Yb 3+ ‐Codoped Bi 2 Ti 2 O 7 Pyrochlore Thin Films

Ho 3+ / Yb 3+ ‐codoped Bi 2 Ti 2 O 7 pyrochlore thin films were prepared by a chemical solution deposition method, and their visible up‐conversion ( UC ) photoluminescence and dielectric relaxation were studied. Ho and Yb can be doped into Bi 2 Ti 2 O 7 lattice and single pyrochlore phase is maintained. Intense visible UC photoluminescence can be observed under the excitation of a 980‐nm diode laser. Two UC emission bands centered at 551 nm and 665 nm in the spectra can be assigned to 5 F 4 , 5 S 2 → 5 I 8 and 5 F 5 → 5 I 8 transitions of Ho 3+ ions, respectively. The dependence of their UC emission intensity on pumping power indicates that both the green and red emissions of the thin films are two‐photon process. In addition, a Stokes near‐infrared emission centered at 1200 nm can be detected, which is due to 5 I 6 → 5 I 8 transition of Ho 3+ ions. The thin films prepared on indium tin oxide–coated glass substrates exhibit a relatively high dielectric constant and a low dielectric loss as well as a good bias voltage stability. The dielectric relaxation of the thin films was also analyzed based on the temperature‐ and frequency‐dependent dielectric properties. This study suggests that Ho 3+ / Yb 3+ ‐codoped Bi 2 Ti 2 O 7 thin films are promising materials for developing multifunctional optoelectronic thin film devices.