Multifunctional Ca9NaZn1-Mg (PO4)7:Eu2+ phosphor for full-spectrum lighting, optical thermometry and pressure sensor applications

The Eu2+ ions in Ca9NaZn(PO4)7:1.0%Eu2+ phosohor occupying the Ca3, Ca1/Ca2, and Na sites bring about a bright yellow light with peaks at about 415, 490, and 570 nm, respectively. The induction effect of Mg2+ ions on Ca9NaZn(PO4)7:1.0%Eu2+ gradually decreases the occupation of Eu2+ in Ca3 site (415 nm), reducing the harm of blue light to human health. Meanwhile, the emission of Eu2+ ions at Na sites emerge a great red shift from 562 to 634 nm due to the change of local environment caused by Mg2+ ions, and the emission color is gradually adjusted from yellow to warm white with increasing the red light component. The color rendering index (CRI) of WLED devices prepared by combination of Ca9NaZn1-yMgy(PO4)7:1.0%Eu2+ (y = 0 and 0.6) phosphors with 375 nm chip promotes from 79.9 to 90.3. Good optical properties of these LED devices confirm the potential of the Ca9NaZn1-yMgy(PO4)7:1.0%Eu2+ phosphors in full-visible-spectrum lighting. In addition, the optical thermometric properties of Ca9NaZn(PO4)7:1.0%Eu2+ phosphors were analyzed in the temperature range of 298–498 K. The maximum relative sensitivity Sr is found to be 0.81% K−1 at 398 K, indicating the potential applications of the Ca9NaZn(PO4)7:1.0%Eu2+ phosphors in optical thermometry. The pressure-dependent luminescence properties of Ca9NaZn(PO4)7:1.0%Eu2+, that is, the red shift of the band centroids and the changes of the band ratios, make the Ca9NaZn(PO4)7:1.0%Eu2+ phosphor suitable for optical pressure sensing (the calculated shift rate dλ/dP ≈ 5.21 nm/GPa).