The paper reports the use of Y2O3 and La2O3 co-doping as a composite sintering additive for the fabrication of γ-AlON transparent ceramics by pressureless sintering. The Y3+ enhanced the mobility of grain boundary and accelerated the grain growth, whereas the La3+ has the opposite effect on grain growth. The sintering additives could cause the formation of liquid phase during sintering, which would greatly promote the densification and eliminate pores. High transparent AlON ceramics with the in-line transmittance of 80.3% at 400 nm wavelength have been prepared when the concentration of sintering additives was 0.12 wt% Y2O3 and 0.09 wt% La2O3.

•The double-emitting blue phosphor Sr3(PO4)2: Eu2+, Dy3+ was prepared.•A broad excitation band between 250 and 450 nm was observed.•Two emission peaks located 410 nm and 485 nm were observed.•Luminescence center Eu2+ occupies both 6-coordinated and 10-coordinated Sr2+ sites.•The phosphor is emission-tunable by varying the Dy3+ concentration.Double-emitting blue phosphor Sr3(PO4)2: Eu2+, Dy3+ was synthesized by solid state reaction under H2 atmosphere. XRD exhibited the pure hexagonal phase of the prepared phosphor. The photoluminescence results showed that all samples had intense broad absorption band between 250 and 450 nm, which matched well with the near-UV (350–420 nm) emission band of InGaN-based chips. The emission spectrum of Sr3(PO4)2: Eu2+, Dy3+ consisted of two broad bands, peaked at 485 nm and 410 nm, which originated from two luminescent centers, related to 4f65d1 → 4f7 transition of Eu2+ in six-coordinated Sr(I) and ten-coordinated Sr(II) sites respectively. The intensity ratio of two emission bands could be easily tuned by adjusting Dy3+ co-doping content, which resulted in color-tunable luminescence in bluish green region to purplish blue region.