Preparation and magnetic and microwave absorption properties of MnNb2O6 ellipsoid-like hierarchical structures
Abstract
Great efforts have been made to synthesize columbite niobates due to their fascinating properties and applications. In this research, ellipsoidal MnNb2O6 crystals have been successfully prepared by a facile hydrothermal method. X-ray powder diffraction patterns showed that the products have the typical orthorhombic columbite structure. Electron microscopy analysis revealed that the obtained MnNb2O6 ellipsoids had a very rough surface, with flaky hierarchical structures composed of nanoparticles with diameters of 10–20 nm. Based on time-dependent experiments, a possible growth mechanism of the ellipsoidal hierarchitectures was also proposed. The magnetization studies demonstrate that the products exhibit antiferromagnetic behavior with a Néel temperature of about 4 K. The microwave absorption properties of the ellipsoidal MnNb2O6 hierarchical structures were also investigated with a vector network analyzer. The absorption peak position moves to a lower frequency with increasing thickness of the sample. The value of the minimum reflection loss is −11.6 dB at 7.8 GHz with a thickness of 3.5 mm, and a reflection loss lower than −10 dB can be obtained in the frequency range of 7.2–8.3 GHz.