A green-emitting phosphor, Eu2+-activated KCaPO4, was synthesized by a conventional solid-state reaction. The phase formation was confirmed by X-ray powder diffraction measurements. The photoluminescence excitation and emission spectra, the temperature-dependent luminescence intensities (293-438 K), and decay curves of the phosphor were measured. With increasing temperature, the emission bands show the abnormal blueshift with broadening bandwidth. The natures of the Eu2+ emission in KCaPO4, e.g., the chromaticity coordinates, the luminescence quenching temperature, and the activation energy for thermal quenching (Delta E), were reported. The excitation spectra have been investigated in the D-5(0) -> F-7(0) region for Eu3+ ions in KCaPO4 by using a pulsed, tunable, and narrow-band dye laser to detect the cation site of Ca2+ in KCaPO4. The multiple sites structure of Eu2+ ions in KMgPO4 lattices were suggested and discussed. (C) 2010 The Electrochemical Society. [DOI: 10.1149/1.3429887] All rights reserved.