Double-site Eu3+ occupation in the langbeinite-type phosphate phosphor toward adjustable emission for pc-WLEDs

Abstract A novel single trivalent Eu ion activated multicolor tunable langbeinite-type phosphor KBaIn2(PO4)3:Eu3+ (abbreviated to KBIP:Eu3+) was successfully synthesized through solid-state reaction. XRD was used to identify the phase of the as-prepared KBIP:Eu3+ phosphor, which proved that the phosphor was pure phase. The refined results showed that In3+ ions occupied two different sites in the KBIP host lattice. The PL spectra shows that the KBIP:Eu3+ phosphor has two luminescent centers, so Eu3+ ions can replace In3+ ions with two different positions. With the change of doping concentration, Eu3+ ions have different occupation orientations in the two sites, and tunable luminescence occurs at different excitation wavelengths. Besides, the morphology, molecular structure and optical properties of the KBIP:Eu3+ phosphors were studied. It is found that the sample crystallizes completely, and the band gap minishes from 2.67 eV to 2.36 eV with the increase of Eu3+ doping content. The fluorescence intensity at 150 ℃ is 65.5% of that at room temperature, and the calculated activation energy is 0.20 eV. The simple LED device test shows that the color rendering index of the phosphor is high (Ra = 92.4%), which greatly improves the red index R9. Therefore, the reported phosphors have great potential application in pc-WLEDs in the future.