Hierarchical three-dimensional cobalt phosphate microarchitectures: Large-scale solvothermal synthesis, characterization, and magnetic and microwave absorption properties

Novel hierarchical cobalt phosphate (α- and β-Co ₂P₂O₇) and cobalt hydrogen phosphate hydroxide [Co₁₁(HPO₃)₈(OH)₆] three-dimensional (3D) architectures with different morphologies were synthesized under a solvothemal condition. The form and shape of cobalt phosphate can be readily tuned by adjusting experimental parameters of the reaction system. The novel hierarchical α-Co₂P₂O₇ microcrystals with basketry-like microstructures were obtained with a molar ratio of Co ²⁺/H₃PO₄/CH₃NH₂/ HO(CH₂)₂OH of 1:1.2:1:108, the reaction temperature of 180 °C, and the reaction time of 5 days; dumbbell-like β-Co ₂P₂O₇ microspheres were formed with the same reaction temperature and time but the molar ratio of 1:1.2:1:54, and Co ₁₁(HPO₃)_g(OH)₆ with peony-like nanostructures was prepared with the same molar ratio and reaction time as β-Co₂P₂O₇ but the reaction temperature of 120 °C. The samples were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), Fourier transform infrared spectra (FT-BR) technologies, a Quantum Design superconducting quantum interference device (SQUID) magnetometer, and a network analyzer. The formation mechanism of cobalt phosphate microstructures was investigated in detail.