Enhanced microwave dielectric performance and thermal stability of La2Mo2O9 –TiO2 composites for microwave S- and C-band applications

This study investigates the influence of TiO 2 addition on the structure, dielectric properties, and performance as dielectric resonator antenna of the La 2 Mo 2 O 9 (LMO) matrix. X-ray diffraction (XRD) analyses revealed that LMO reacted with TiO 2 during sintering, resulting in the formation of additional crystalline phases in the composites. The microwave dielectric properties were directly influenced by TiO 2 addition. The relative permittivity values (ε' r ) initially decreased for the LMO80 sample, followed by an increase in the other compositions. This behavior can be attributed to the crystalline phases formed, as well as to the increased contribution of TiO 2 . Furthermore, all composites exhibited a reduction in the loss tangent (tan δ) compared to pure LMO, indicating improved dielectric performance. The thermal stability was evaluated using the temperature coefficient of resonant frequency (τ f ), with values ranging from −256.0 to +104.0 ppm.°C −1 . Among the investigated compositions, the LMO70 composite showed the τ f value closest to zero (τ f = +23.0 ppm.°C −1 ). Numerical simulations were also conducted to assess the suitability of the composites for use as dielectric resonator antennas (DRAs). The simulated devices showed reflection coefficients (S 11 ) values below −10 dB within specific frequency ranges, radiation efficiency exceeding 83%, bandwidths at –10 dB between 180 and 894 MHz, and gain above 4.70 dBi. These results demonstrate that composites investigated exhibit promising performance for application in electronic devices operating in the S and C bands.