The spectrally tunable inorganic solid solutions discovered in the past years generally cannot show the spectral tuning properties without either using external rare earth (RE) (e.g., Eu2+, Ce3+) and non-RE (e.g., Mn2+, Bi3+) ions, or using the coupling arrangement of these RE/non-RE ions as the luminescent activator(s). Herein, we report a type of external dopant-free Sc(Px,V1-x)O4 (0.0 < x < 1.0) solid solutions that features the color tuning, enhanced photoluminescence (PL) intensity, and improved thermally-induced PL quenching stability. Our powder X-ray diffraction (XRD) and PL findings show that gradual substitution of larger V5+ ions with smaller P5+ ions not only leads to the decrease of lattice parameters a(b)c and Sc-O bond lengths and the shrinkage of cell volume (V), but also causes an initial redshift of emission position from 495 nm to 524 nm as the x increases to 0.2 followed by a subsequent blueshift back to 457 nm for 0.2 < x ≤ 0.9. Meanwhile, an enhancement of ~40% of the room temperature emission intensity at x = 0.3, along with the improved thermal PL quenching after adding an appropriate amount of P5+ content, are observed in the Sc(Px,V1-x)O4 (0.0 < x < 0.9) solid solutions. Through a combined analysis and discussion of density functional theory (DFT) and dielectric electronegativity calculations as well as the UV-vis diffuse reflectance and temperature-dependent PL spectral measurements, we reveal that the origin of this unusual yet regular spectral tuning and the improved PL properties is mostly arising from the interplay of the bandgap energies adjustment, the bond covalency regulation, and the possible presence of significant amount of oxygen vacancies, together with the closing structural rigidity caused by the lattice microenvironment modification. This work not only can provide insights into designing and discovering new external dopant-free inorganic solid solutions with color tunability, enhanced emission intensity, and improved thermally-induced PL quenching behavior, but also allows to gaining better understanding on how the key parameters to govern the spectral tunability in the virgin (or doped) zircon crystal systems.
- Tunable solid solution
- DFT simulation
- Dielectric electronegativity theory
- Oxygen vacancies