K-band microwave absorption analysis of sol–gel synthesized cobalt-substituted zinc spinel ferrites

Cobalt-substituted zinc spinel ferrites having chemical composition Zn 1− x Co x Fe 2 O 4 with stoichiometric proportion ‘ x ’ equals 0.00, 0.25, 0.50, 0.75, and 1.00 have been synthesized by sol–gel citrate route sintered at 1000 °C for 6 h. All the fabricated specimens have been characterized by using X-ray diffraction, scanning electron microscopy, energy-dispersive spectroscopy, Raman spectroscopy, and vector network analyzer. The XRD patterns ensured the existence of a cubic spinel crystal structure having single phase of space group Fd -3 m . Decline in crystallite size ( D c ) from 48.016 to 45.314 nm with an increase in cobalt content displayed the nanocrystalline nature of the synthesized specimens. The values of lattice constant ( a avg , a px , a true , and a th ) obtained from four different approaches are perfectly coordinating with each other. The complex electromagnetic parameters ( ε r and μ r ) measured by VNA are found to be increasing with Co 2+ doping in K-band (18–26.5 GHz) frequency range. The reflection loss study revealed that all the synthesized compositions have yielded more than 90% absorption intensity in the studied frequency band due to higher magnetic and dielectric losses of the synthesized ferrites thereby making them a potential candidate for the implementation of microwave absorbers at higher frequencies.