Abstract By controlling the pH values of prepared solutions, the 10 mol% Ce 3+ , 5 mol% Tb 3+ co-doped KGdF 4 (synthesized with pH = 3) and the 10 mol% Ce 3+ , 5 mol% Tb 3+ co-doped GdF 3 (synthesized with pH = 1) submicro/nanocrystals have been synthesized based on a citric acid assisted hydrothermal method. For comparison, the samples synthesized by co-precipitation method (without hydrothermal treatment) with pH = 3 and 1 were also collected. The X-ray diffraction data illustrate that the hydrothermal treated KGdF 4 sample crystallizes in the cubic phase and the GdF 3 sample crystallizes in the orthorhombic phase. However, the samples synthesized by co-precipitation method with pH = 3 and 1 are both cubic phase KGdF 4 . The field emission scanning electron microscopy images suggest that the hydrothermal treated KGdF 4 submicro/nanocrystals present spherical morphology and the GdF 3 submicrocrystals are rhombic-shaped. And the photoluminescence excitation and emission spectra as well as the luminescent dynamic curves demonstrate the difference in optical properties of the two hydrothermal treated samples.