Via a fast, facile and environmentally-friendly microwave-assisted ionic liquid method, binary rare earth fluoride REF₃ (RE = La–Lu, Y) nano/microcrystals with multiform crystal structures (hexagonal and orthorhombic) and morphologies (nanodisks, secondary aggregates constructed from nanoparticles, and elongated nanoparticles) have been successfully fabricated. The experimental results indicate that the use of microwave irradiation and ionic liquid [BIBM][BF₄] are responsible for the products. Microwave irradiation accelerates dramatically the reaction rate and shortens the reaction time. [BIBM][BF₄] plays multiple roles as solvent, reactant and template. The possible formation mechanisms for REF₃ nano/microcrystals with diverse well-defined morphologies have been presented in detail. Additionally, we systematically investigate the magnetic and luminescent properties of the GdF₃ : Ce³⁺/Ln³⁺ (Ln = Eu, Tb and Dy). They show paramagnetic property with mass magnetic susceptibility value of 1.10 × 10⁻⁴ emu g⁻¹ Oe at 300 K, and red (Eu³⁺), green (Tb³⁺) and blue (Dy³⁺) emissions due to the Ce³⁺ → Ln³⁺ (Ln = Tb, Eu, and Dy) energy transfer. This energy transfer occurs through the energy migration process like Ce³⁺ → Gd³⁺→ (Gd³⁺)_n → Ln³⁺ and the Gd³⁺ ions plays an intermediate role in the process.