Down-conversion Photoluminescence Properties of ZrO<inf>2</inf>: Ln³⁺ (Ln = Eu, Sm, Er, Tb, Ho, Tm, Pr, Gd, Dy) Films Formed by Plasma Electrolytic Oxidation

Abstract

Down-conversion photoluminescent ZrO2: Ln3+ (Ln = Eu, Sm, Er, Tb, Ho, Tm, Pr, Gd, Dy) films were prepared by the plasma electrolytic oxidation (PEO) method from a pure zirconium foil, by adding Ln2 O3 particles to a basic electrolyte. Photoluminescence (PL) emission spectra of ZrO2: Ln3+ films are characterized by a broad band of ZrO2 host with a maximum positioned at about 490 nm and sharp emission bands ascribed to 4f–4f transitions of Ln3+ ions. The most intense 4f–4f transitions of Ln3+ are 5 D 0  →  7 F2 at 613 nm for Eu3+,4 G5/2  → 6 H7/2 at 617 nm for Sm3+,4 S3/2  → 4 I15/2 at 548 nm for Er3+,5 D4  → 7 F5 at 543 nm for Tb3+,5 F4  → 5 I8 at 540 nm for Ho3+,1 D2  → 3 F4 at 456 nm for Tm3+,3 P0  → 3 H6 at 608 nm for Pr3+,6 P7/2  → 8 S7/2at 313 nm for Gd3+, and4 F9/2 → 6 H13/2at 578 nm for Dy3+. Ln3+ ions in ZrO2 host can be directly excited into 4f levels. For Eu3+ more efficient excitation is through charge transfer band caused by electron transfer between the completely filled 2p orbital of O2− ions and the partially filled 4f orbital of Eu3+, while for Tb3+ through the inter-configurational 4f8  → 4f7 5d1 transition.