Encapsulation of nitride phosphors into sintered phosphate glass by pressureless firing and hot isostatic pressing

The encapsulation conditions of Eu²⁺-doped calcium silicon nitride ((Ca_0.90Eu_0.10)₂Si₅N₈) and strontium silicon nitride ((Sr_0.98Eu_0.02)₂Si₅N₈) phosphors into phosphate glass ((50-x)Na₂O–xZnO–5B₂O₃–45P₂O₅; x = 10-40) were examined by pressureless sintering (normal or infrared firing) and subsequent oxygen-assisted hot isostatic pressing. The evaluation of water resistivity, as well as glass transition temperature (T_g), indicated that the excellent water resistivity and low T_g (313°C) could be achieved at x = 30. The colorless and clear glass body could be fabricated by infrared firing at 370°C for 20 minutes in air, followed by the hot isostatic pressing at 370°C for 24 hours (80%Ar + 20%O₂, pressure: 130 MPa). The encapsulations of 3.0 mass% (Ca_0.90Eu_0.10)₂Si₅N₈ and (Sr_0.98Eu_0.02)₂Si₅N₈ into the glass body produced reddish orange light emission (peak wavelength: 604 nm under excitation wavelength of 423 nm) and red-light emission (617 nm under 383 nm), respectively, showing higher chemical and thermal stability of nitride phosphors in the glass matrix.