A new resource-rich carbonate luminescent host KNa5Ca5(CO3)8: A case study activated by Eu3+ for red-phosphor purpose

Abstract

Exploring and designing new luminescent host with rich resource is beneficial to reducing the cost and the large-scale application of luminescent materials. Herein, a series of novel Eu3+-activated KNa5Ca5(CO3)8 red-emitting phosphors with different Eu3+ concentrations were successfully synthesized under mild hydrothermal condition. XRD and SEM characterizations show that all as-prepared KNa5Ca5(CO3)8:Eu3+ samples crystallize in a hexagonal structure, P63mc (No.186) space group, and show monodispersed hexagonal sheet morphologies, within a side length interval about of 2–3 μm and a thickness of about 0.6 μm. Eu3+ doping within 6 mol% concentration has little influence on the crystal structure of the host, as indicated by XRD, and FT-IR results, but thermal stability changes as shown by the TG-DTA. KNa5Ca5(CO3)8 phosphors with different Eu3+ concentrations can emit red-light under effectively excitation by near-UV light. CIE chromaticity coordinates of all KNa5Ca5(CO3)8:Eu3+ phosphors were calculated to locate in red region, and CCT of each sample is the range from 2815 to 3650 K, very close to the tungsten lamp light. Besides, concentration quenching phenomenon appearing at 5 mol% is found to be the result of electric multipolar interaction of Eu3+ activators, and the decay lifetime is about 1.63 ms, which almost unchanges with Eu3+ doping concentration. Importantly, thermal quenching analysis reveals good thermal stability with thermal activation energy of about 0.216 eV. The results reported here demonstrate that KNa5Ca5(CO3)8 is a promising fluorescent host for LEDs applications.