Influence of partial substitution of Fe3+ with W3+ on the microstructure, humidity sensitivity, magnetic and electrical properties of barium hexaferrite

This paper investigates the influence of partial substitution of iron with tungsten on the properties of barium hexaferrite. The BaWxFe12−xO19 hexaferrite samples were prepared by using a sol-gel autocombustion technology. The powder ferrites were heat treated for 30 min at 1000 °C. The samples were investigated by using X-ray diffraction in order to highlight the differences between the phase compositions of comparative samples. The influence of the substitution of tungsten ions on the size and shape of the crystallites was revealed by the scanning electron microscopy. The investigations of the substitution of tungsten were focused mainly on magnetic and electrical properties of the BaWxFe12−xO19 ferrites; the measurements of electrical properties were performed in different humidity conditions, aimed at obtaining a ferrite useful as a material support for capacitive or resistive humidity sensors. In this respect, the partial substitution of iron with tungsten contributes to an increasing of permittivity and to a reduced electrical resistivity of the material, without significantly lowering its sensitivity to humidity.