[Synthesis of the CaCO3:Eu3+ red phosphor by microwave method]

The red phosphor of CaCO3 doped with Eu3+ was synthesized with the microwave method in the aqueous solution and characterized with electron microscope (SEM), X-ray diffraction (XRD), and photoluminescence and photoluminescence excitation (PL-PLE) spectrum. Also under investigation was the influence of microwave power on luminescence properties. The results showed that the synthesized CaCO3:Eu+ particles were the mixture of various particles in the forms of vaterite with flower-flake, calcite with cubic shape and aragonite with needle-like, which were evenly dispersed. The Eu3+ ion as the luminescent center inhabited the site of Ca3+ in mixed phases of CaCO3:Eu3+. This feature was mainly characterized by the intense charge transfer band range from 200 to 300 nm in the PLE spectrum, which was the wide band excitation. Moreover, the narrow excitation peaks at 319, 395, 465, 535 nm and so on could be detected in the PLE spectrum. For the mixed phase, the magnetic-dipole transition (5)D0 to (7)F1 emission was split into two sublevels at about 589 and 593 nm by the crystal field. The mainly emission peaks were located in the vicinity of 614 and 620 nm, corresponding to the electric dipole transition (1)D0-->(7)F2 of Eu3+ ions that was the pure red emission. Moreover, with the improvement of the microwave power, the emission intensity was on rise for the morphology and phase of the sample changed from the flower-flake vaterite to the needle-like aragonite, coupled with the intensity of red light emission.