Effect of temperature on shielding efficiency of phosphate-bonded CoFe2O4 – xBaTiO3 multiferroic composite ceramics in microwaves

Abstract

A series of novel CoFe2O4 – xBaTiO3 (x = 0.6–0.9) phosphate-bonded multifunctional ceramic composites were synthesized and studied both in ‘Salisbury screen’ geometry and as free-standing films in the frequency range of 25–54 GHz and temperature interval of 120–500 K. Experiments prove that the studied system is prospective for shielding applications in both modes providing total transmission losses of the free-standing sample layer of 40 dB for x = 0.9 dominated by absorption and more than 40 dB of reflection losses at resonant conditions in the Salisbury screen geometry. It was demonstrated that the electromagnetic response of multiferroic composite ceramics in microwaves is very sensitive to the temperature changes in the application's significant temperature range, i.e. 150 – 400 K. Notably, a small, i.e. 5 – 10 K, temperature variation drastically changes the shielding efficiency of the Salisbury screen (SER). In particular, SER ≥ 40 dB is achieved in the range of 302–309 K for the sample with x = 0.9, outside of the range SE rapidly decreases to 10–15 dB. The impact of temperature has to be considered for the efficient use of shielding materials in Ka and V bands for different applications.

Keywords

• Phosphate-bonded ceramics
• Barium titanate
• Cobalt ferrite
• EMI shielding efficiency
• Microwaves