TECHNICAL FIELD

The present invention relates to a phosphor powder, a composite, and a light-emitting device.

BACKGROUND ART

As nitride and oxynitride phosphors, an α-sialon phosphor in which a specific rare earth element is activated is known to have useful fluorescence characteristics, and has been applied to a white LED and the like. The α-sialon phosphor has a structure in which Si—N bonds of α-silicon nitride crystals are partially substituted with Al—N bonds and Al—O bonds, and specific elements (Ca, Li, Mg, Y, or lanthanide metals except for La and Ce) penetrate into crystal lattices and are solid-dissolved in order to maintain electrical neutrality. The fluorescence characteristics are expressed by using some of the elements that penetrate into the lattices and are solid-dissolved as a rare earth element serving as a luminescent center. Among those, the α-sialon phosphor, in which Ca is solid-dissolved and the elements thereof are partially substituted with Eu, is relatively efficiently excited in a wide wavelength range from ultraviolet to blue light and exhibits emission of yellow to orange light. As an attempt to further improve the fluorescence characteristics of such an α-sialon phosphor, for example, it has been proposed to select an α-sialon phosphor having a specific average particle diameter by a classification treatment (Patent Document 1).

RELATED DOCUMENT

Patent Document

[Patent Document 1] Japanese Laid-open Patent Publication No. 2009-96882

SUMMARY OF THE INVENTION

Technical Problem

In recent years, a higher brightness of a white LED has been demanded. For example, a further improvement in the light emission characteristics of a phosphor powder used for the white LED has also been required.

The present invention has been made in view of the problems. An object of the present invention is to provide a phosphor powder having improved light emission characteristics.

Solution to Problem

According to the present invention, there is provided a phosphor powder composed of α-sialon phosphor particles containing Eu, in which in a case where an internal quantum efficiency after the phosphor powder is held at 600° C. for 1 hour in an air atmosphere is defined as P1 and an internal quantum efficiency after the phosphor powder is held at 700° C. for 1 hour in an air atmosphere is defined as P2, P1 is equal to or more than 70% and (P1−P2)/P1×100 is equal to or less than 2.8%.

Furthermore, according to the present invention, there is provided a composite including the above-mentioned phosphor powder and a sealing material that seals the phosphor powder.

In addition, according to the present invention, there is provided a light-emitting device including a light-emitting element that emits excitation light, and the above-mentioned composite that converts a wavelength of the excitation light.

Advantageous Effects of Invention

According to the present invention, it is possible to provide a technique relating to a phosphor powder having improved light emission characteristics.

