A novel thermally-stable red phosphor CaYGaO4:Eu3+ for WLEDs and anti-counterfeiting ink

Abstract

In this paper, CaYGaO4:xEu3+ (CYGO:xEu3+)phosphors were synthesized for the first time using a high-temperature solid-state method. The samples were characterized by X-ray diffractometer (XRD) and scanning electron microscope (SEM). Their energy dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS) were used to further investigate the microscopic composition of the samples. The forbidden bandwidths and densities of states of CYGO and CYGO:0.25Eu3+ were calculated by first principles methods. The emission and excitation spectra of the samples were tested by fluorescence spectroscopy, which showed that the samples can be excited by both UV and blue light. When the sample heated to 473 K, the luminescence intensity under 393 and 463 nm excitation stays at 83.99 % and 85.19 % of the room temperature, respectively, which demonstrates that CYGO:0.3Eu3+ possesses excellent thermal stability. The color coordinates (CIE), correlated color temperature (CCT) and color purity (CP) of the samples were also investigated. In order to explore its application in the field of white light-emitting diodes (WLEDs), CYGO:0.3Eu3+ was mixed with commercial blue and green phosphors in a certain ratio, and the chip was made into a WLED with 395 nm excitation, and the CIE of the lamps were (0.3338, 0.3521), with a correlated CCT of 5448 K, and a color rendering index (CRI) of Ra = 86.2. The thermal imaging performance of the small lamps was also evaluated for sustained usage, revealing minimal temperature fluctuations and excellent thermal stability. Consequently, CYGO:Eu3+ exhibits promising potential for applications in the field of WLEDs. Additionally, CYGO:0.3Eu3+ was selected as a representative sample for the creation of fluorescent ink and its subsequent application on various media. The outcomes indicate that this phosphor possesses promising potential for use in the field of anti-counterfeiting ink technology.