Luminescence Properties of Eu3+ and Mn2+ Doped Tungstate and Phosphate Materials

Abstract

As a new generation of display and lighting source, white LED has the characteristics of high efficiency, energy-saving, green environmental protection, no pollution, sturdiness, long life, fast switching, and easy maintenance. It is one of the most promising high-tech fields in the world in recent years. Combining phosphors with ultraviolet, near ultraviolet or blue light chips is one of the important ways to realize white LEDs. As a key and technically important component of white LEDs, phosphors are of great significance in improving and improving the luminous efficiency, color rendering index, service life and other technical indicators of white LEDs. Therefore, it is necessary to continuously explore and develop new and efficient phosphor material. Rare earth luminescent materials have a widely applicated in the fields of light-conversion luminescent materials such as energy-saving lighting, medical imaging, modern information technology and display detection, and phosphor luminescent materials with high efficiency, stability and good luminescent properties are also used in white LEDs and other applications. significance. Tungstate host materials are often selected as valuable luminescent materials due to their good chemical stability, high luminescence intensity, self-luminescence, and easy preparation. Therefore, the self-activated tungstate matrix and Eu3+-doped tungstate matrix materials have extensive research and application significance. In this study, Eu3+ ions doped Ca3WO5Cl2 was prepared by the facile high temperature solid-state reaction. The PL-PLE spectra, crystal structure, temperature-dependent luminescence, and decay lifetimes were investigated. Under the excitation of UV light, the pure Ca3WO5Cl2 emitted the typical self-activated luminescence from the charge transfer (CT) transitions in [WO5Cl]5- groups. With the increasing temperature from room temperature to 480 K, the emission intensity decreases, and the emission band shifts to blue. Such reduction due to thermal quenching wherein emission centers are thermally activated through the crossing point between the ground and the excited levels. The concentration dependent emission spectra of Ca3WO5Cl2:Eu3+ shows the characteristic emission peaks of Eu3+ ions can be observed in the red emission region at around 615 nm both with the host emission band in the blue emission region at around 450 nm. Accordingly, the band at 450 nm originates from charge transfer behavior of WO5Cl group, while the sharp lines at 615 nm originates from the 5D0-7F2 transitions of Eu3+ ions. As the Eu3+ concentration increases, the luminescence intensity of the Eu3+ ions increase, while that of the WO5Cl group band decreases rapidly. The temperature dependent emission spectra indicate Ca3WO5Cl2:Eu3+ phosphor has good thermal stability. Therefore, the results indicate the possibility of present phosphor for Near UV (394 nm excitation), blue LED (450 nm excitation) applications in white light diodes with high thermal stability. Phosphate system phosphor is an important traditional light-emitting material. Phosphate matrix has good physical and chemical stability, low synthesis temperature, low production cost, complex structure, and can strongly absorb ultraviolet light to achieve high-efficiency emission in the visible spectrum, and widely used. In this study, the traditional high-temperature solid-state reaction method was used to synthesize Mn2+-doped Na2Mg(PO3)4 phosphors. The structure was conducted on the basis of X-ray diffraction (XRD), the photoluminescence excitation (PLE) and emission (PL) spectra reveal that the Na2Mg(PO3)4:Mn2+ red phosphor could be excited by ultraviolet (UV) to blue light from 300 to 500 nm, and shows a broadband emission in the spectral region from 550 to 750 nm. The optimum doping concentration of Mn2+ ions in Na2Mg(PO3)4 lattice was measured to be 9 mol% based on the concentration-dependent PL spectra. To deeply study the thermal stability of Na2Mg(PO3)4:Mn2+ red phosphor, temperature dependent PL spectra and decay curves were measured at various temperature ranging from 10 to 500 K. It is demonstrated that Na2Mg(PO3)4:Mn2+ red phosphors can be simulated as potential materials to produce high-efficiency white-light.