Processes for preparing color stable red-emitting phosphor particles having small particle size

A Mn+4 doped phosphor of formula I comprising a monodisperse population of particles having a particle size distribution comprising a D50 particle size of less than 1 μm;

• Ax[MFy]:Mn+4 I
• wherein
• A is Li, Na, K, Rb, Cs, or a combination thereof;
• M is Si, Ge, Sn, Ti, Zr, Al, Ga, In, Sc, Y, La, Nb, Ta, Bi, Gd, or a combination thereof;
• x is the absolute value of the charge of the [MFy] ion;
• and
• y is 5, 6 or 7;
• wherein an aspect ratio of a plurality of particles of the population is less than or equal to 3/1,
• wherein the phosphor has a quantum efficiency exceeding 85% under blue excitation,
• wherein the phosphor comprises an amount of manganese ranging from about 1.82 wt % to about 5.1 wt % based on total phosphor weight, and
• wherein the phosphor is coated with a manganese-free shell comprising KMgF3.

A Mn+4 doped phosphor of formula I comprising:

• a monodisperse population of particles having a particle size distribution comprising a D50 particle size of less than 10 μm;
• Ax[MFy]:Mn+4 I
• wherein
• A is Li, Na, K, Rb, Cs, or a combination thereof;
• M is Si, Ge, Sn, Ti, Zr, Al, Ga, In, Sc, Y, La, Nb, Ta, Bi, Gd, or a combination thereof;
• x is the absolute value of the charge of the [MFy] ion;
• and
• y is 5, 6 or 7;
• wherein an aspect ratio of a plurality of particles of the population is less than or equal to 3/1;
• and
• wherein the phosphor is coated with a manganese-free shell comprising KMgF3.

A Mn+4 doped phosphor of formula I comprising:

• a monodisperse population of particles having a particle size distribution comprising a D50 particle size of less than 10 μm;
• Ax[MFy]:Mn+4 I
• wherein
• A is Li, Na, K, Rb, Cs, or a combination thereof;
• M is Si, Ge, Sn, Ti, Zr, Al, Ga, In, Sc, Y, La, Nb, Ta, Bi, Gd, or a combination thereof;
• x is the absolute value of the charge of the [MFy] ion;
• and
• y is 5, 6 or 7;
• wherein an aspect ratio of a plurality of particles of the population is less than or equal to 3/1,
• wherein the phosphor has a quantum efficiency exceeding 85% under blue excitation,
• wherein the phosphor comprises an amount of manganese ranging from about 1.82 wt % to about 5.1 wt % based on total phosphor weight;
• and
• wherein the phosphor is coated with a manganese-free shell comprising KMgF3.