The τ-phase-Ba_1.3Ca_0.7SiO₄ phosphors co-doped with 3 mol% Dy³⁺ and ~1-5 mol% Tb³⁺ trivalent rare-earth ions were prepared by the gel-combustion method. The structure-property relation of the samples was examined by X-ray diffraction, scanning electron microscopy, and spectrophotometer. Here, the effect of Tb³⁺’s concentration on the spectroscopic properties of Dy³⁺/Tb³⁺ co-doped Ba_1.3Ca_0.7SiO₄ phosphors was explored by using the photoluminescence excitation, emission, and decay curves. Importantly, the photonic energy transfer from (Dy³⁺: ⁴F9/2 + Tb³⁺: ⁷F₆) to (Dy³⁺: ⁶H_15/2 + Tb³⁺:⁵D₄) was observed, in which the Dy³⁺ ions acts as a light-emitting donor whereas the Tb³⁺ ions as a light-absorbing acceptor, resulting in an enhanced emission from the co-doped Ba_1.3Ca_0.7SiO₄: Dy³⁺/Tb³⁺ phosphors. Finally, the chromaticity coordinates were determined from the measured emission spectra, locating at the green and white light regions. This observation indicates that the characteristic emission color could be tuned from white to green by varying Tb³⁺ concentrations under ultraviolet light.

X-ray diffraction (XRD) measurements (Model Philips Bruker D8 advance) were carried out to examine the structure and phase of the prepared phosphor materials. The scanning electron microscope (SEM) (Model JEOL JSM-7800F) was used to characterize the morphology of phosphors as a function of composition. Energy-dispersive X-ray spectroscope (EDX) (Oxford Aztee) was used to confirm the composition of elements in the Ba_1.3Ca_0.7SiO₄: Dy³⁺/Tb³⁺ samples. The PL emission and decay spectra were investigated using Cary Eclipse fluorescence spectrophotometer (Model LS-55) equipped with a xenon flash lamp to act as the excitation source.

<XRD_Data>

Two columns: X-axis: 2theta (degree) and Y-axis: Intensity (a.u.)

XRD_Dy3mol% Tb1mol%.csv (Dy 3 mol% and Tb 1 mol % doped phosphor sample XRD)

XRD_Dy3mol% Tb2mol%.csv(Dy 3 mol% and Tb 2 mol % doped phosphor sample XRD)

XRD_Dy3mol% Tb3mol%.csv (Dy 3 mol% and Tb 3 mol % doped phosphor sample XRD)

XRD_Dy3mol% Tb4mol%.csv (Dy 3 mol% and Tb 4 mol % doped phosphor sample XRD)

XRD_Dy3mol% Tb5mol%.csv (Dy 3 mol% and Tb 5 mol % doped phosphor sample XRD)

<PL_Data> PL Data_Excitation and Emission

Two columns: X-axis: Wavelength (nm) and Y-axis: Intensity (a.u.)

PL Data_Emission Dy3+ 3mol% Tb3+ 1mol%

PL Data_Emission Dy3+ 3mol% Tb3+ 2mol%

PL Data_Emission Dy3+ 3mol% Tb3+ 3mol%

PL Data_Emission Dy3+ 3mol% Tb3+ 4mol%

PL Data_Emission Dy3+ 3mol% Tb3+ 5mol%

PL Data_Excitation Dy3+ 1mol% Tb3+ 1mol%

PL Data_Excitation Dy3+ 2mol% Tb3+ 2mol%

PL Data_Excitation Dy3+ 3mol% Tb3+ 3mol%

PL Data_Excitation Dy3+ 4mol% Tb3+ 4mol%

PL Data_Excitation Dy3+ 5mol% Tb3+ 5mol%

<EDX data>

EDX data: Dy3+ 3 mol% and Tb3+ 1 mol % phosphor sample – EDX data

EDX data: Dy3+ 3 mol% and Tb3+ 2 mol % phosphor sample – EDX data

EDX data: Dy3+ 3 mol% and Tb3+ 3 mol % phosphor sample – EDX data

<SEM data>

Various SEM images as a function of composition and magnification.

<CIE color coordinate> Example

Calculated CIE color coordinates for emission in the co-doped Ba1.3Ca0.7SiO4:0.03Dy3+/xTb3+ (x=0.01-0.05) phosphors. 

Here, 3 mol% and 4 mol% Tb3+ doped phosphor showed almost overlapped data.