As a promising replacement for nitride red phosphors, Ce: Y-3(Mg1.8Al1.4Si1.8)O-12(Ce: YMASG) ceramic phosphors have attracted significant attention recently for their advantages in inorganic encapsulation and massive red-shifting of Ce(3+)emission. In this work, Ce: YMASG with different doping concentrations of Ce(3+)and Al2O3, was fabricated by vacuum sintering to investigate its effects on the elimination of the impurity phase and the enhancement of the luminescent properties of white light-emitting diodes (w-LEDs). It was discovered that the emission wavelength redshifts from 592 to 606 nm as the Ce(3+)concentration increases, while at 450 K, the emission intensity deteriorates from 0.47 to 0.36 of its initial value. The Rietveld analysis revealed the presence of an impurity phase of Y(4)MgSi(3)O(13)with a concentration of 17.021 wt% in Ce: YMASG. With the introduction of Al2O3, the impurity phase was eliminated from the matrix completely, the emission peak shifted to a shorter wavelength, and the thermal stability was greatly improved. When the correlated color temperature was controlled at around 3000 K in the packaged w-LEDs, the commission international de l'eclairage (CIE) chromaticity coordinates shifted toward the bottom left corner of the diagram with increasing concentration of Ce3+. Conversely, the luminous efficiency (LE) increased from 36 lm/W to 58.6 lm/W as the concentration of Al(2)O(3)increased from 0 to 10 wt%, which demonstrated the application prospect of the fabricated phosphor in warm w-LEDs.