Novel alpha-SiAlON:Eu2+-based yellow oxynitride phosphors with the formula Sr0.375-x Eu (x) (2+) Si12-m-n Al (m+n) O (n) N16-n (m = 0.75, n = x = 0.004-0.04) have been prepared by firing the powder mixture of SrSi2, alpha-Si3N4, AlN, and Eu2O3 at 2,000 A degrees C for 2 h under 1 MPa nitrogen atmosphere. The luminescence properties, the dependence of the activator concentration of Eu2+ and the thermal stability of Sr-alpha-SiAlON:Eu2+ phosphor have been investigated in comparison with Ca-alpha-SiAlON:Eu2+ phosphor. Similar to Ca-alpha-SiAlON:Eu2+ phosphor, Sr-alpha-SiAlON:Eu2+ phosphor has the excitation wavelength ranging from the ultraviolet region to 500 nm, and exhibit intense yellow light. The strongest luminescence was achieved at about x = 0.02 with the emission peak at 578 nm, slightly shorter than that of Ca-alpha-SiAlON:Eu2+ phosphor at 581 nm. Temperature-dependent emission intensity of Sr-alpha-SiAlON:Eu2+ phosphor is comparable to that of Ca-alpha-SiAlON:Eu2+ phosphor. The results suggest that the different position of the emission peak for Sr- and Ca-alpha-SiAlON:Eu2+ depends on the composition and the Stokes shift, and the thermal stability is nearly independent of Sr and Ca or fixed by the network of (Si, Al)-(O, N) in alpha-SiAlON at the same Eu2+ concentration.