Fabrication of rare-earth fluoride films via a sacrificial template method from layered rare-earth hydroxide (LRH) films: phase transition mechanism and near infrared light response†

Abstract

Rare-earth fluoride films of REF₃ (RE = La, Pr, Nd) and NaREF₄ (RE = Sm, Eu, Gd, Tb, Dy, Ho, and Y) were fabricated within 1 hour at 100 °C and pH ∼ 7 via a sacrificial template method, using electrodeposited layered rare-earth hydroxide (LRH) films as templates and NaF as an anion source. By investigating the phase transition from layered gadolinium hydroxide (LGdH) templates to NaGdF₄ films, the dissolution–recrystallization mechanism governing this transformation was elucidated. The Yb³⁺/Er³⁺ co-doped NaGdF₄ film exhibited significant up-conversion luminescence from Er³⁺ under 980 nm excitation. A NaGdF₄:Yb,Er/Bi₂S₃ composite film was subsequently fabricated using the successive ionic layer adsorption and reaction (SILAR) method and deployed as a photoanode in a standard electrochemical cell, generating measurable photocurrent in aqueous media. This work provides a promising strategy for the preparation of rare earth fluoride thin films and achieves infrared light collection through a composite with semiconductors, with potential applications in solar cells, photocatalysts, and infrared light detectors.