Oxide fluorescent material, light emitting device, and method for producing oxide fluorescent material

An oxide fluorescent material, having a composition comprising:

• at least one first element M1 selected from the group consisting of Li, Na, K, Rb, and Cs;
• at least one second element M2 selected from the group consisting of Mg, Ca, Sr, Ba, and Zn;
• at least one third element M3 selected from the group consisting of B, Al, Ga, In, and rare earth elements;
• at least one fourth element M4 that comprises Ge and optionally comprises at least one element selected from the group consisting of Si, Ti, Zr, Sn, Hf, and Pb;
• O (oxygen);
• Cr;
• and
• optionally at least one fifth element M5 selected from the group consisting of Eu, Ce, Tb, Pr, Nd, Sm, Yb, Ho, Er, Tm, Ni, and Mn,
• wherein the composition is represented by the following formula (1):
• M1tM2uM3vM45Ow:Crx,M5y (1)
• wherein t, u, v, w, x, and y each satisfy 0.7≤t≤1.3, 1.5≤u≤2.5, 0.7≤v≤1.3, 12.9≤w≤15.1, 0.001≤x≤0.2, 0≤y≤0.10, and y<x, and
• wherein the oxide fluorescent material has a light emission peak wavelength in a range of 782 nm or more and 1,050 nm or less in a light emission spectrum of the oxide fluorescent material and having a full width at half maximum in a range of 123 nm or more and 400 nm or less in the light emission spectrum.