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Sr‐containing α‐SiAlON (Srm/2Si12‐m–nAlm+nOnN16–n:Eu2+) phosphor was obtained as a major phase in compositions having small m and n values, by firing the powder mixture of SrSi2, SrO, α‐Si3N4, AlN, and Eu2O3 at 2000°C for 2 h under 1 MPa nitrogen atmosphere. The crystal structure of Sr‐α‐SiAlON was refined by the Rietveld analysis of the synchrotron X‐ray powder diffraction pattern. The crystal structure showed that the Sr–N2 bonding distance of Sr‐α‐SiAlON was fairly large compared with that of Ca‐α‐SiAlON. The displacement of N2 sites probably allow the interstices in α‐SiAlON to accommodate the introduction of the large Sr ion. Sr‐α‐SiAlON:Eu2+ phosphor has an excitation wavelength ranging from the ultraviolet region to 500 nm and emits a strong yellow light.

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Orthorhombic Ca1−xEuxAlzSiN2+z polycrystalline powders have been synthesized by a solid‐state reaction at high temperature in a nitrogen atmosphere. The smaller lattice parameters compared with the single crystal and charge distribution analysis indicate that impure oxygen might be incorporated into the lattice. Ca1−xEuxAlzSiN2+z shows red emission at about 630 nm due to the transition of 4f65d1→4f7 when excited within 375–450 nm. With an increase in the Eu2+ concentration and z, the quantum efficiency of Ca1−xEuxAlzSiN2+z was significantly decreased due to concentration quenching and high photoionization. First‐principle molecular orbital calculations suggest that the overall luminescence of Eu2+ may be mainly originated from the small Eu(1) center. CaSiN2:Eu2+ is a potential red conversion phosphor for white LED applications.