Luminescent properties of the Sr8−xBaxMgY(PO4)7:Eu2+ solid solution

Abstract

Photoluminescence generated by substituting rare-earth ions on multiple crystallographically independent cation sites within a crystalline host material is one of the most common approaches for creating a full-spectrum phosphor-converted white light-emitting diode (pc-wLED). In this work, a series of complex orthophosphates with the composition (Sr8−xBax)0.99Eu0.08MgY(PO4)7 (x = 0, 1, 2, 3) were synthesized via high-temperature solid-state synthesis. These materials possess five potential substitution sites achieving broadband (5905 cm−1) yellow photoluminescence through multi-site substitution showing a violet-excited photoluminescent quantum yield of nearly 50%. Developing such an efficient broad emission spectrum is crucial for enhancing the color rendering ability of pc-wLEDs. Varying the Sr2+ to Ba2+ shifts the emission color from green-yellow to yellow under violet excitation (λex = 400 nm) while influencing the full-width-at-half-maximum (fwhm). Temperature-dependent photoluminescence measurements indicate that phosphor has good thermal stability with T50, the temperature at which the emission intensity is half of the low-temperature intensity, at 420 K and stable chromaticity coordinates, further supporting that the (Sr8−xBax)0.99Eu0.08MgY(PO4)7 series are promising candidates for LED white lighting. Constructing a prototype pc-wLEDs device using (Sr7Ba)0.99Eu0.08MgY(PO4)7, the highest quantum yield phosphor, produced a functional daylight bulb with a color rendering index (CRI) of 90.

Keywords

• Solid state lighting
• Inorganic phosphor
• Photoluminescence
• Whitlockite