Effect of alumina addition on the microstructure and luminescence properties of BaAl2O4:Eu2+-Al2O3 green fluorescent composite ceramics fabricated by spark plasma sintering

Abstract

BaAl2O4:Eu2+ green phosphors were prepared by the solid state reaction method. The structural and optical properties of phosphors with different Eu ions doping concentrations and thermal treatment temperatures were investigated. Then the Ba0.97Al2O4:Eu2+0.03 (BAO:Eu2+0.03) phosphor powders were sintered into ceramics by spark plasma sintering (SPS). In addition, different amounts of alumina were added to fabricate composite ceramics, aiming to improving the thermal conductivity and the light extraction efficiency. X-ray diffraction θ-2θ scans showed that hexagonal BaAl2O4 was the only crystalline phase in the BaAl2O4–Al2O3 composite, which implied that an amount of glass phase may be formed. The addition of alumina also has the effect on limiting the grain growth of BaAl2O4. In addition, the amount of pores was obviously reduced in the composite ceramics, which may be attributed to the improved densification brought by the glass phase. The BAO:Eu2+0.03-15w% Al2O3 composite ceramic has the highest luminescence intensity, which was 2.8 times as high as that of the BAO:Eu2+0.03 ceramic. And the thermal conductivity of the BAO:Eu2+0.03-15 wt% Al2O3 composite ceramics is 1.6 times as high as that of BAO:Eu2+0.03 ceramics. This indicates introduction of alumina can improve the heat removal capability and enhance the luminescence output of the BaAl2O4:Eu2+ fluorescent ceramic.