科研之友
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摘要
Monodispersed spheres (monospheres) of the rare-earth orthophosphate (REPO4, RE = La-Lu in the lanthanide family and Y, excluding radioactive Pm) have been originally synthesized via fast microwave irradiation of mixed solutions containing RE3+, phosphoric acid, urea and sulfate anions. Through systematic and in-depth investigations into the influences of heating method (microwave and water-bath), SO42- /RE3+ molar ratio, sulfate source, PO43-:Y3+ molar ratio and solution pH, the mechanisms of morphology evolution were unveiled. The effects of lanthanide contraction and post calcination on the phase structure and particle morphology of the products were also clarified. The key feature of this technique is utilizing microwave heating to promote burst nucleation of REPO4 and SO42- anions to efficiently aggregate the nuclei/subunits into monospheres. The photoluminescence of various RE3+ activators (RE = Ce, Pr, Sm, Eu, Tb, Dy, Er and Tm) was comprehensively elaborated with YPO4 as a representative host lattice, and the thermal quenching of Eu3+ emission was also investigated. The microwave assisted homogeneous precipitation technique established in this work for REPO4 may have wide implications to the generation of other types of inorganic monospheres.
