Hydrothermal Synthesis and Electromagnetic Characteristics of α-MnO2 Nanorods

alpha a-MnO2 nanorods were prepared with hydrothermal method using manganese sulfate (MnSO4 center dot H2O) and potassium permanganate (KMnO4) as raw materials in a stainless-steel autoclave at 160 degrees C for 48 h. The crystalline structure, morphology and microstructure of the products were characterized by XRD, FESEM and TEM. The temperature dependent dielectric properties in the frequency ranges 1 kHz to 1 MHz were also discussed at the temperature 223 K to 393K. The results show that the products are tetragonal alpha-MnO2, nanorods with straight and smooth surfaces. Its diameter is about 30 nm and lengths are up to 0.5-1 mu m. The dielectric constants and dielectric loss tangents all increase with temperature and decrease with frequency. With the decreasing of temperature, there turns less difference between the dielectric loss tangents at different frequencies.