High thermal stability and colour saturation red-emitting Ba2AGe2O7: Eu3+ (A = Mg, Zn) phosphors for WLEDs

Abstract Two series of Eu3+ ions activated high performance red-emitting phosphors Ba2(1-x)AGe2O7: 2xEu3+ (A = Mg, Zn, 0 ≤ x ≤ 0.2) were synthesized by high-temperature solid-state procedure. The research results showed that the host lattice Ba2MgGe2O7 possess higher band gap than that of Ba2ZnGe2O7, and all the Ba2(1-x)MgGe2O7: 2xEu3+ (BMGO: 2 xEu3+, 0 ≤ x ≤ 0.2) and Ba2(1-x)ZnGe2O7: 2xEu3+ (BZGO: 2 xEu3+, 0 ≤ x ≤ 0.2) phosphors crystallized in a tetragonal unit cell with the space group of P421 m (113). Compared with other phosphors in the same series, the samples BMGO: 0.30 Eu3+ and BZGO: 0.25 Eu3+ presented the highest absorption intensity when monitoring at 616 nm under 395 nm excited, respectively. Moreover, the samples BMGO: 0.30 Eu3+ and BZGO: 0.25 Eu3+ not only exhibited high color purity of 90% and 90.3%, respectively, but also possess excellent thermal stability. Unsurprisingly, the WLED devices based on BMGO: 0.30 Eu3+ and BZGO: 0.25 Eu3+ as the red-emitting components displayed good luminescence properties, especially the color rendering index (CRI, Ra) R9 represented the saturation of colour of illuminated objects exhibited a high value of 89.6 and 82.3, respectively. In contrast, the WLED device based on BMGO: 0.30 Eu3+ as red-emitting phosphors presented better electroluminescence performances than those of BZGO: 0.25 Eu3+ on account of its much favorable crystal structure, PL performance and thermal stability.