Structure, photoluminescence, Judd–Ofelt analysis, and thermal stability studies of Ho3+/Yb3+ Co-doped YNbO4 green phosphors

A series of YNbO4:Ho3+/Yb3+ phosphors with varying concentrations of Yb3+ were synthesized using a high-temperature solid-state method. To ascertain the presence, structure, and purity of YNbO4:Ho3+/Yb3+, the crystal structure of the luminescent powder was investigated through x-ray diffraction. Trivalent rare earth ion-doped transparent luminescent materials possess distinctive f–f transition properties, which can be comprehensively studied using the Judd–Ofelt theory. However, when dealing with opaque powder materials, traditional Judd–Ofelt (J–O) theory becomes challenging to apply due to the unavailability of absorption spectra measurements. In this paper, to analyze the properties of Ho3+ in the YNbO4 phosphors, diffuse diffraction spectra and fluorescence decay curves were employed within the framework of the J–O theory. Furthermore, the J–O parameters Ωλ (λ = 2, 4, 6) of Ho3+ in YNbO4 phosphors were calculated and subsequently modified for accuracy and precision.