Phase stability, microstructure, and dielectric properties of quaternary oxides In12Ti10A2BO42 (A: Ga or Al; B: Mg or Zn)

Quaternary oxides In12Ti10Al2BO42 (ITAM), In12Ti10Al2BO42 (ITAZ), In12Ti10Ga2MgO42 (ITGM), and In12Ti10Ga2ZnO42 (ITGZ), were synthesized by the solid-state reaction method and the dielectric behavior is reported. The samples were submitted to different sintering temperatures (1473-1773 K) for 24 hours and the phase stability and microstructure were analyzed by X-ray powder diffraction (XRD) and scanning electron microscopy (SEM). It is found that the phase decomposition occurs above of 1573 K. Microstructure images showed an increase in the grains size as sintering temperature was raised. The dielectric permittivity as a function of temperature and frequency showed acceptable dielectric constant (15-30) and low dielectric loss (tan delta << 1) values in a wide range of temperature. The band gap obtained by the optical spectrum analysis is about 3.5 eV indicating good dielectric insulating compounds. Furthermore, the electrical conductivity, the activation energy, and the conduction mechanisms are analyzed and discussed in a whole range of temperature. The good dielectric values, epsilon' (15-20) and tan delta (similar to 0.004), and their behavior (almost independent of the frequency and temperature) almost constant within a wide range of temperature make these quaternary oxides interesting in electroceramic applications.