Tunable Optical\nProperties, Enhanced Photoluminescence,\nand Thermostability of CaO: Eu<sup>2+/3+</sup> Phosphors by Codoping\nCl<sup>–</sup> Ions

Europium-activated calcium oxide (CaO: Eu) phosphor shows\ngreat\npotential in the fabrication of light-emitting diodes (LEDs). However,\nits luminescent intensity and thermostability still need to be further\nenhanced. In this work, the photoluminescence property and thermostability\nof CaO: Eu<sup>2+/3+</sup> were improved significantly by codoping\na few of Cl<sup>–</sup> ions into it. Compared with CaO: Eu<sup>2+/3+</sup> samples, CaO: Eu<sup>2+/3+</sup>, Cl<sup>–</sup> phosphors not only have tunable luminescence but also show stronger\nluminescence intensity and thermal stability. The emission color of\nphosphors can be tuned by changing the excitation wavelength; typically,\nstrong red/blue light can be displayed under 250/362 nm excitation.\nMore importantly, both the red and blue emissions will increase simultaneously\nwith increasing codoped Cl<sup>–</sup> content. When the Cl<sup>–</sup> ion content is 0.06, the emission intensity of CaO:\n0.01Eu<sup>2+/3+</sup>, 0.06Cl<sup>–</sup> reaches its maximum\nand its red and blue emission intensities increase by approximate\n2.5 times and 13.2 times, respectively. The results show that CaO:\nEu<sup>2+/3+</sup>, Cl<sup>–</sup> phosphors have potential\napplication value in LEDs and anti-counterfeiting.