Crystal Structure and Optical and Magnetic Properties of Pr₂(MoO₄)₃

Praseodymium molybdate Pr₂(MoO₄)₃ was synthesized using the standard ceramic route. The crystal structure of the material has been successfully solved in superspace group I2/b(αβ0)00 with lattice constants a = 5.30284(4), b = 5.32699(3), c = 11.7935(1) Å, γ = 90.163(1)°, and the modulation vector q = 2/3a* + 0.88810(2)b*. The deviation of the q vector from a rational value allows a description of the structure in terms of nanosize domains with the La₂(MoO₄)₃-like structure separated by stacking faults. Under 450 nm excitation, (³P₀ level) Pr₂(MoO₄)₃ exhibits the characteristic red emission, with the most intense band at 649 nm corresponding to a ³P₀ → ³F₂ transition. Magnetic susceptibility measurements reveal Curie−Weiss paramagnetism with predominating antiferromagnetic interactions between Pr³⁺-magnetic moments and no evidence of magnetic transitions down to T = 5 K.