Novel red phosphors KBaEu(XO 4 ) 3 (X = Mo, W) show high color purity and high thermostability from a disordered chained structure

• Published in: Dalton transactions : an international journal of inorganic chemistry 2017-05, Vol.46 (20), p.6776-6784
• Main Authors: Wang, G Q, Gong, X H, Chen, Y J, Huang, J H, Lin, Y F, Luo, Z D, Huang, Y D
• Format: Article
• Language: English
• ISSN: 1477-9226; 1477-9234
• DOI: 10.1039/c7dt01044c

Two novel red phosphors KBaEu(XO ) (X = Mo, W) have been synthesized by high-temperature solid-state reactions and the crystal structures were determined for the first time. Single-crystal X-ray diffraction data reveal that their space groups are C2/c. The crystalline structure is constituted of K/BaO distorted square antiprisms and distorted EuO polyhedra which form chains lying along the c-axis and two kinds of distorted XO tetrahedra. This high disorder of K/Ba which might lower the crystal field symmetry around Eu results in the high purity of red emission around 615 nm originating from D → F transition under near-ultraviolet (NUV) excitation. With increasing temperature, the luminescence of KBaEu(XO ) (X = Mo, W) phosphors decreases almost linearly with subtle alteration for the CIE coordinate. As the temperature reaches 550 K, the red emission intensity decreases to 37.3% and 50.7% of that at 300 K for KBaEu(MoO ) and KBaEu(WO ) , respectively. The analysis of the decay curves of the D → F emission at variable temperatures indicates the weak cross relaxation and non-radiative energy transfer between Eu ions. These results demonstrate that the investigated phosphors are attractive for application in high power NUV excited white LEDs.