Red-emitting improvement of CaAlSiN₃:Eu²⁺ phosphor-in-glass: Insight into the effect of atmospheric pressure preparation on photoluminescence properties and thermal degradation

The red-emitting phosphor-in-glass (PiG)s have been successfully prepared by a facile one-step co-sintering method on the basis of ultra-low melting Sn-P-F-O glass and CaAlSiN₃: Eu²⁺ red phosphors synthesized under atmospheric-pressure (denoted as CASN-AP) and high-pressure (denoted as CASN-HP), respectively. The crystal structure, particle morphology, photoluminescence (PL) properties and surface states of the phosphors were investigated detail by X-ray powder diffraction (XRD), field emission electron microscopy (FESEM), fluorescence spectroscopy and X-ray photoelectron spectroscopy (XPS). Under excitation of blue light (460 nm), CASN-AP phosphor with red emission at 659 nm shows a higher luminescent intensity by 23 % than that of CASN-HP phosphor. Moreover, a shorter photoluminescence lifetime and red shift of 9 nm for emission peak can be also found for the CASN-APphosphor, which is ascribed to the increased Si-N bonds and surface Si/N ratio (1.86) demonstrated by the XPS analysis. Besides, the quantum yield and thermal degradation of both phosphors have been investigated. CASN-AP phosphor exhibits higher emission intensity because of its more emitting photons, but a lower quantum yields than CASN-HP phosphor due to its more absorbed photons. Based on the above, the low-temperature melting process for Sn-P-F-O glass does not damage the phosphor and the enhanced (≥35%) red-emitting CASN-AP PiG will be a promising candidate for essential red component in high quality white LEDs.