Oxide phosphor, light-emitting device, and method for producing oxide phosphor

An oxide phosphor having a composition comprising Mg, Ga, O, and Cr, the composition optionally including:

• at least one first element M1 selected from the group consisting of Ca, Sr, Ba, Ni, and Zn;
• at least one second element M2 selected from the group consisting of B, Al, In, and Sc;
• and at least one third element M3 selected from the group consisting of Eu, Ce, Tb, Pr, Nd, Sm, Yb, Ho, Er, Tm, and Mn,
• wherein, when a total molar ratio of Ga, Cr, the second element M2, and the third element M3 per mole of the composition of the oxide phosphor is 2, a molar ratio of Mg or a molar ratio of a total of Mg and the first element M1 when the first element M1 is included is in a range of 0.7 to 1.3,
• a molar ratio of O is in a range of 3.7 to 4.3,
• a molar ratio of Cr is in a range greater than 0.02 and 0.3 or less, and
• further, when a molar ratio of a total of Mg and the first element M1 is 1, a molar ratio of the first element M1 is in a range of 0 to 0.8, and
• a molar ratio of the second element M2 is in a range of 0 to 1.6, a molar ratio of the third element M3 is in a range of 0 to 0.2, the molar ratio of the third element M3 being smaller than the molar ratio of Cr, and
• wherein the oxide phosphor has a light emission peak wavelength in a range of 800 nm to 1600 nm.

A method for producing an oxide phosphor, the method comprising:

• preparing a raw material mixture comprising a first compound containing Mg, a second compound containing Ga, and a third compound containing Cr, and optionally a fourth compound containing at least one first element M1 selected from the group consisting of Ca, Sr, Ba, Ni, and Zn, and optionally a fifth compound containing at least one second element M2 selected from the group consisting of B, Al, In, and Sc, and optionally a sixth compound containing at least one third element M3 selected from the group consisting of Eu, Ce, Tb, Pr, Nd, Sm, Yb, Ho, Er, Tm, and Mn,
• wherein the raw material mixture has a composition in which when a total molar ratio of Ga, Cr, the second element M2, and the third element M3 per mole of the composition is 2, a molar ratio of Mg, or when the first element M1 is included, a molar ratio of a total of Mg and the first element M1 is in a range of 0.7 to 1.3, a molar ratio of Cr is in a range greater than 0.02 and 0.3 or less, when a molar ratio of a total of Mg and the first element M1 is 1, a molar ratio of the first element M1 is in a range of 0 to 0.8, a molar ratio of the second element M2 is in a range of 0 to 1.6, a molar ratio of the third element M3 is in a range of 0 to 0.2, and the molar ratio of the third element M3 is smaller than the molar ratio of Cr;
• and
• obtaining an oxide phosphor by heat-treating the raw material mixture in an atmosphere containing oxygen at a temperature in a range of 1200° C. to 1700° C.,
• wherein at least one selected from the group consisting of the first compound, the second compound, and the third compound is an oxide.