Phosphor and light-emitting device

A β-type sialon phosphor represented by the following expression 1, wherein D50 is 4.3 μm or less, and values of D10, D50, and D90 satisfy a relationship of the following expression 2 with respect to D10, D50, and D90 (each unit is [μm]) on a volume frequency basis as measured according to a laser diffraction/scattering method:

• Si12-aAlaObN16-b:Eux Expression 1
• where 0<a≤3;
• 0<b≤3;
• 0<x≤0.1
• (D90−D10)/D50<1.6 Expression 2
• where the D10, D50, and D90 (each unit is [μm]) on a volume frequency basis as measured according to the laser diffraction/scattering method are each a measurement value obtained with a liquid obtained by loading 0.5 g of a phosphor for measurement, into 100 ml of a solution of 0.05% by weight of sodium hexametaphosphate mixed in ion-exchange water, and subjecting the resultant to a dispersing treatment for 3 minutes with an ultrasonic homogenizer at an oscillation frequency of 19.5±1 kHz and an amplitude of vibration of 32±2 μm, with a chip being placed at a central portion of the liquid, and
• an average particle size DBET [μm] calculated from a specific surface area measured according to a BET method and the D50 [μm] measured according to a laser diffraction/scattering method, of the β-type sialon phosphor, satisfy a relationship of the following expression 3:
• D50/DBET<2.1. Expression 3