LI-CONTAINING --a-- or --ALPHA-- SIALON-BASED PHOSPHOR, PRODUCTION PROCESS THEREOF, LIGHTING DEVICE AND IMAGE DISPLAY DEVICE

A process of producing an Li-containing α-sialon-based phosphor represented by formula (1):

• LixEuySi12−(m+n)Al(m+n)On+δN16−n−δ (1)
• wherein, assuming that average valence of Eu is a, x+ya+δ=m;
• 0.45≦x<1.2, 0.001≦y≦0.2, 0.9≦m≦2.5, 0.5≦n≦2.4, and δ>0;
• the process comprising:
• i) weighing and mixing
• a silicon nitride powder and/or a nitride-containing silane compound,
• an aluminum source containing at least aluminum nitride,
• a nitride, oxynitride or oxide of Li or a precursor substance capable of becoming an oxide of Li by pyrolysis, and
• a nitride, oxynitride or oxide of Eu or a precursor substance capable of becoming an oxide of EU by pyrolysis, to produce a composition of the Li-containing α-sialon-based phosphor represented by formula (1) provided that lithium is contained in an amount in excess over a theoretical amount of Li in the Li-containing α-sialon-based phosphor represented by formula (1) by 0.1 mole or more per 1 mole of the Li-containing α-sialon-based phosphor, and
• ii) firing a mixture obtained by said mixing at 1,400 to 1,800° C. in a nitrogen-containing inert gas atmosphere under atmospheric pressure.