1：Experimental Design and Method Selection:

The study uses plasma electrolytic oxidation (PEO) to form Er3+/Yb3+ doped ZrO2 coatings on zirconium substrates in an alkaline electrolyte containing Er2O3 and Yb2O3 particles. The PEO process is chosen for its ability to incorporate rare earth ions into oxide coatings through micro-discharges.

2：Sample Selection and Data Sources:

Commercial zirconium substrates (

3：95% purity, Alfa Aesar) are used. Electrolyte compositions vary with concentrations of Er2O3 and Yb2O3 particles up to 4 g/L in a supporting electrolyte of 10 g/L Na3PO4·12H2O. Samples are coded S1 to S7 based on particle concentrations. List of Experimental Equipment and Materials:

Equipment includes a PEO setup (described in Ref. [15]), scanning electron microscope (SEM, JEOL 840A) with energy dispersive spectrometer (EDS, OXFORD) and wavelength dispersive X-ray fluorescence spectrometer (XRF, Shimadzu XRF-1800), X-ray diffractometer (XRD, Rigaku Ultima IV with Ni-filtered Cu Kα radiation), and spectrofluorometer (Horiba Jobin Yvon Fluorolog FL3-22) with a 450 W xenon lamp and a 980 nm diode laser. Materials include zirconium, Na3PO4·12H2O, Er2O3, and Yb2O3 particles.

4：Experimental Procedures and Operational Workflow:

PEO is performed at a constant current density of 150 mA/cm2 for 15 minutes with electrolyte temperature maintained at 20±2°C. Coatings are analyzed for morphology (SEM), chemical composition (EDS and XRF), phase composition (XRD), and photoluminescence properties (down-conversion with 280 nm and 379 nm excitations, up-conversion with 980 nm excitation). All measurements are at room temperature.

5：Data Analysis Methods:

XRD data are analyzed using integrated intensities to calculate weight fractions of monoclinic and tetragonal ZrO2 phases. PL spectra are corrected for system response and lamp distribution. Energy transfer mechanisms are interpreted based on emission and excitation spectra.