Photoluminescence evolution and high thermal stability of orange red-emitting Ba3-xSrxZnNb2O9: Eu3+ phosphors

Highlights: • A serious of orange red-emitting Ba_3-xSr_xZnNb₂O₉: 0.3Eu³⁺ phosphors were synthesized successfully. • The occupancy conditions of Eu³⁺ ion is discussed through the refined results of XRD. • The blue-shift of the emission peaks have been explained by the theory of crystal field splitting in the luminescent center. A series of Ba_3-xSr_xZnNb₂O₉: 0.3Eu³⁺ (x=0, 0.5, 1, 1.5, 2, 2.5, 3) orange-red phosphors were synthesized by high-temperature solid-phase reaction. In order to identify and describe the crystal structure, luminescence characteristics and thermal stability of the samples, XRD and luminescence spectroscopy tests were carried out. The refined XRD results showed that Eu³⁺ ions have been successfully doped into Ba_3-xSr_xZnNb₂O₉ matrix and occupied partly the sites of Eu³⁺ ions. Under UV excitation of 396nm, the emission spectra of the samples are composed of two emission peaks near 593nm and 612nm with a slight blue shift, attributed to the increase in splitting degree of 5d electron orbit of Eu³⁺ ions. At 523K, the thermal stabilities of phosphors with Sr²⁺ ion doping concentration of 2 and 3 are 82.14% and 84.33%, respectively. With the increase of Sr²⁺ ion concentration, the activation energy increases from 0.198eV to 0.230eV, better than the other reports. In addition, the CCT (below 2000 K) and color purity (above 95%) of the samples are calculated. A WLED device can be obtained by combining the as-prepared orange red-emitting phosphor with commercial blue (BaMgAl₁₀O₁₇: Eu²⁺) and green ((Sr, Ba)₂SiO₄: Eu²⁺) phosphors. All these indicated that the self-made phosphors are promising to be used in UV/n-UV pumped WLEDs requiring low CCT.