Novel blue and green phosphors obtained from K2ZrSi3O9:Eu2+ compounds with different charge compensation ions for LEDs under near-UV excitation

Abstract

The structural properties of wadeite (K₂ZrSi₃O₉) have been investigated using high-resolution transmission electron microscopy and X-ray powder diffraction refinement, and the luminescence properties of Eu²⁺ activated K₂ZrSi₃O₉ have been studied to explore new material for phosphor-converted white light near-ultraviolet light-emitting diodes (NUV-LEDs). Eu²⁺ was introduced into the K₂ZrSi₃O₉ host in a reducing atmosphere, and the special crystallographic positions of Eu²⁺ were determined based on XRD, photoluminescence emission spectra, temperature dependence properties, and time-resolved photoluminescence. The calculated band gap is about 4.7 eV. The CIE chromaticity coordinates and FWHM of the blue phosphor K₂ZrSi₃O₉:1%Eu²⁺ are (0.1538, 0.1857) and 57 nm respectively. The photoluminescence properties of co-doped Eu²⁺–Al³⁺and Eu²⁺–Sc³⁺ charge compensation pair phosphors were investigated. The Eu²⁺ single-doped K₂ZrSi₃O₉ phosphor shows blue emission with a broad band peaking at 465 nm upon 400 nm NUV excitation. With Eu²⁺–Al³⁺ as the charge compensation pair, the photoluminescence properties do not change distinctly, while the photoluminescence emission spectrum red shifts by about 39 nm and the emission becomes green with the Eu²⁺–Sc³⁺ pair. Different occupation locations of the different charge compensation pairs were discussed. Blue and green emissions can be obtained from K₂ZrSi₃O₉:Eu²⁺ compounds by different charge compensation mechanisms. This reveals that K₂ZrSi₃O₉:Eu²⁺ possesses remarkable optical properties and can be used in NUV-LEDs.