Comparative Study on Photoluminescent Properties of CaGdAlO4: Eu3+ Phosphors Synthesized with Three Methods

CaGdAlO4Eu3+ powder phosphors were prepared using citrate sol-gel (CSG), half-dry and half-wet (HDW) and solid state (SS) methods, respectively. X-ray diffraction results confirm the formation of CaGdAlO4: Eu3+ at 900 °C. (CSG), 1200 °C (HDW) and 1400 °C (SS), respectively. Field emission scan electron microscopy (FE-SEM) images show that the GaGdAlO4: Eu3+ powder prepared by the CSG and HDW method has an elliptical shape and that prepared under the SS method has a flaky shape. Upon excitation with 280 nm UV light, all the CaGdAlO4: Eu3+ powders show bright red emission on account of the 4f-4f transitions of the Eu3+ ions. Moreover, the size of the phosphor particles and the emission intensity increase with the increase of calcined temperature. At the same calcination temperature of 1400 °C, the 5D0 → 7F2 emission intensity of the sample prepared by HDW method is the highest. Stark components of the 5D0 → 7Fj emission transitions, both at room temperature and at a low temperature, reveal that the Eu3+ ions occupy only one site with non-centrosymmetry in the crystals.