Solvent-Free Synthesis of Rare-Earth-Doped Zirconia Ceramic Nanofiber Films with Enhanced Luminescence for Anti-Counterfeiting and Warm White Lighting

Abstract

To overcome the limitations of brittleness and aggregation-caused quenching of traditional inorganic phosphors, we developed highly flexible rare-earth (RE³⁺)-doped zirconia (ZrO₂) ceramic nanofiber films via a solvent-free electrospinning and calcination approach. Density functional theory (DFT) calculations and X-ray photoelectron spectroscopy (XPS) analyses reveal that oxygen vacancies (VO) formed during charge compensation stabilize the high-symmetry cubic phase, serving as the key mechanism for phase regulation. By co-doping La³⁺ or Lu³⁺ in ZrO₂:Eu³⁺, the cubic phase proportions increased to 45.4% and 61.0%, respectively, while absolute photoluminescence quantum yields (PLQY) reached 93.6% and 94.7%. This enhancement is attributed to the optimized crystal field symmetry around Eu3+ and suppressed non-radiative transitions facilitated by V_O. The flexible films exhibit excellent bendability and long-term stability. Under 254 nm/365 nm UV illumination, ZrO₂:La³⁺/Eu³⁺, ZrO₂:Lu³⁺/Eu³⁺, ZrO₂:Lu³⁺/Er³⁺, and ZrO₂:Lu³⁺/Tm³⁺/Er³⁺ films emit bright red, red, green, and multicolor fluorescence respectively, with no performance degradation observed over 180 days of testing. For WLEDs, ZrO₂:1.40Lu³⁺,2.25Eu³⁺,1.60Dy³⁺ ceramic nanofiber films encapsulated on near-UV chips yield warm white light (CCT = 3708 K, CRI = 72) via Dy³⁺→Eu³⁺ energy transfer, maintaining stable performance without decay over 200 h of continuous operation.