The  constant  scientific  breakthrough  contributes  to  the  emerge  of  multifunctional  materials,  aiming  to  supply  the  world  demand  for  technology. Therefore, the study and development of materials is associated to Material Chemistry understanding. In this scenario, the present thesis aims the application of the four Material Chemistry pillars (synthesis, characterization, properties, and applications) in an inorganic nanocomposite production rich in bismuth cobaltite, with a sillenite crystalline structure (sillenite Co – Co3O4) as a promising candidate to various applications. In a first study, two polycrystalline samples of the nanocomposite were prepared by combustion and sol-gel routes, with crystalline size from 64.4 nm to 80 nm of all phases. Combustion sample presented a diffractogram with small asymmetry in its sillenite peaks, indicating the presence of sillenite s with variation in its stoichiometry. From the magnetic susceptibility, it was verified that the combustion sample has a degree of magnetic frustration twice that of the sol-gel sample. Both samples presented Néel temperature of 36 K for secondary phase Co3O4 and a hysteresis at 6 K. However, in M-T measurements with 200 Oe, above 148 K, just the combustion sample presented a superparamagnetic signal, and this signal decreases to 70 K when a 600 Oe magnetic field is applied. In a second work, directed to nanocomposite application, it was reported the production and characterization of sillenite Co – Co3O4 powder, using combustion route. The nanocomposite dielectric characterization presented interesting results in X-band, with low conductivity and loss tangent from 6.0 GHz to 8.5 GHz, allowing its application as resonator’s substrate. Thus, the nanocomposite was applied as a substrate in a microstrip patch antenna. Reflection coefficient measurements presented good agreement with the simulations, reaching a maximum  error of 0.39% in resonance frequency, validating the  morphological and dielectric characterizations, according to antenna’s design. In a third investigation, the nanocomposites synthesis optimization was performed using Box-Behnken design and the study of structural, chemical, and dielectric properties were also performed using three types of fuels applied to sol-gel combustion synthesis: urea, glycine, and ethylene glycol. Fourteen samples were prepared combining the sol-gel and combustion methods to evaluate the effects of fuel type, along with fuel percentage and initial pH in mass concentration of Co sillenite (% CoS). Validation experiments confirmed the good predictive potential of the proposed quadratic model in % CoS control of the nanocomposites, w ith the ethylene glycol sample presenting the higher % CoS, reaching 87.92%.