M-type barium ferrites Ba(CoTi)(1.20)Fe9.6O19 were synthesized with 5.0 wr% Bi2O3 additive at low temperatures in an oxygen atmosphere. For temperatures increasing from 900 degrees C to 945 degrees C, the saturation magnetization (M-s) increased first and then decreased. However, coercivity (He) decreased first and then increased. Superfluous Bi2O3 produced BiFeO3 dielectric phase with Fe3+ ions. When the samples were processed in an oxygen atmosphere, the magnetic and dielectric properties were obviously increased, in particular, the real permeability (mu') and real permittivity (epsilon'). The processed materials exhibited nearly equivalent real permeability and real permittivity (at 935 degrees C, mu' approximate to epsilon' approximate to 420.6), and had low magnetic loss (tan delta(mu) approximate to 0.05) and low dielectric loss (tan delta(epsilon) approximate to 0.004) at the frequency of 100 MHz. The results showed the Bi2O3 enhanced M-type barium ferrite was an excellent substrate material for high frequency antenna applications. (C) 2017 Elsevier Ltd. All rights reserved.