Single-hole hollow tetragonal LaVO4:Eu3+ microspheres prepared by Ostwald ripening and their luminescence property

Single-hole hollow tetragonal (t-) LaVO4:Eu3+ microspheres have been synthesized with the assistance of ethylene diamine tetraacetic acid (EDTA, or H4L, where L4− = (CH2COO)2N(CH2)2N(CH2COO)24−]) from a hydrothermal system of water and ethylene glycol (EG) via a hydrothermal process. Single-hole hollow LaVO4:Eu3+ microspheres with well-defined morphology and single structure of tetragonal phase are obtained with the adding volume of EG = 3.2 mL at pH = 4 for 48 h. The obtained hollow LaVO4:Eu3+ microspheres are 1–3 μm in diameter with holes in their shells in the diameter of several hundreds nanometers. The dense shells are about 100 ~ 200 nm in the thickness, and there are orderly tetragonal nanorods with an average diameter about 8 nm and aspect ratio about 10 on their surface. The forming process is investigated by the variation of the reaction time, the pH value of the initial solution, and the adding volume of EG. A formation mechanism is proposed involving the nucleation, aggregation and Ostwald ripening accompanying the oriented growth of nanorods. The holes in the shell form as a result of both the connection of neighboring nanoparticles outside the microspheres during the Ostwald ripening process and the mass transfer in the oriented growth of t- LaVO4:Eu3+ nanorods. Furthermore, single-hole hollow t- LaVO4:Eu3+ microspheres exhibit excellent red emission.