Influence of wastewater sludge pyrolysis char as dopants on the microstructure and electromagnetic wave absorbing properties of iron deficient Mn-Zn ferrite (Zn0.75Mn0.75Fe1.5O4) based on microwave induced sintering method

- Microwave-induced pyrolysis ash of wastewater sludge was utilized effectively.
- Iron deficient ferrite was prepared with wastewater sludge ash as dopants.
- Quality of iron deficient ferrite crystals doped with pyrolysis ash was enhanced.
- Electromagnetic properties of iron deficient ferrites with dopants were improved.

Iron deficient Mn-Zn ferrite was prepared by doping the microwave induced pyrolysis char of wastewater sludge. The effects of doping with different dosages of pyrolysis char on the crystallization phase, micromorphology, crystal microstructures, electromagnetic parameters and microwave absorbing properties were investigated. The iron deficient ferrite samples with microwave sintering at a temperature of 900 °C had a spinal structure, and the main crystallization phase was Zn0.75Mn0.75Fe1.5O4. The crystal grains with the dopants of 20 wt% were homogeneous, and the average grain size was about 36.80 nm. The crystal of ferrite with dopants of 20 wt% had a clear grain boundary, and the crystallinity degree reached 94.76%. Moreover, the electromagnetic parameters (permittivity and permeability) of Zn0.75Mn0.75Fe1.5O4 ferrites were changed due to the dopants improving the electromagnetic wave absorbing properties. The electromagnetic wave reflection loss of the Zn0.75Mn0.75Fe1.5O4 ferrite samples with the dopants of 20 wt% increased to −4.2 dB.

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