Morphology-controlled synthesis and microwave absorption properties of β-MnO2 microncube with rectangular pyramid

•β-MnO2 microncube has been synthesized via a simple aqueous chemical route.•The crystal type changed from γ-MnO2 to β-MnO2 and the morphology changed to a microncube with rectangular pyramid.•The evolution process of the β-MnO2 structure is proposed to involve two main stages.•β-MnO2 has certain dielectric loss properties.•An effective absorption bandwidth of 3.5 GHz was achieved from the β-MnO2/paraffin wax composite.

β-MnO2 microncube is a novel morphology of microncube with rectangular pyramid. It has been synthesized for the first time via a simple aqueous chemical route under hydrothermal conditions without any templates. When the reaction time is increased from 1 h to 10 h, the crystal type changed from γ-MnO2 to β-MnO2 and the morphology changed from an urchin-like shape to a microncube with rectangular pyramid. We propose a possible growth mechanism for intrinsic structural growth mechanism, the evolution process of the β-MnO2 structure is proposed to involve two main stages. Besides, the electromagnetic properties of the synthesized β-MnO2 were investigated. It shows that β-MnO2 has certain dielectric loss properties and an effective absorption bandwidth (reflection loss lower than − 10 dB) of 3.5 GHz was achieved from the β-MnO2/paraffin wax composite.