A Novel Method for Improving Particle Growth and Photoluminescence through F- Substituting for Gallery NO3- in Layered Y/Eu Hydroxides

Abstract We demonstrated a novel methodology to promote particle growth via introducing anions, here F−, into the precursor structure, which utilized the exchangeability of NO3− anions resided in the gallery of layered Y/Eu hydroxide (LY/EuH, simply (Y/Eu)2(OH)5NO3·nH2O) nanosheets. LY/EuH was prepared by one-step freezing temperature crystallization method. Through anion-exchange reaction at room temperature, F− substituted for NO3−, and LY/EuH transformed into F−-exchanged layered Y/Eu hydroxide (LY/EuHFx, simply (Y/Eu)2(OH)z(NO3)yFx·nH2O). The phase, particle size and photoluminescence of annealed particles strongly depended on the fluorine content. Fluorine accelerated the collapse of sheet morphology and significantly promoted the particle growth. The product calcined at 1300 °C from LY/EuH consisted of particles around 200 nm in size. In contrast, the size of particles calcined at 1300 °C from LY/EuHF0.8 increased by 7.5 times, up to 1.5 μm, and the photoluminescence intensity at 613 nm increased by 1.5 times. During calcination, the oxidation reaction, including the uptake of oxygen and the outward diffusion of fluorine contained in intermediates Y2O3−y/2Fy and YOF, in conjunction with the melt of YOF, is believed to promote the mass transfer and thus accelerate particle growth. After the oxidation reaction completion, both Y2O3−y/2Fy and YOF transformed into cubic Y2O3, without leaving residues. This novel methodology exhibits great advantages and provides significant insight into the synthesis of high performance inorganic phosphors.