Sintering and Dielectric Characterization of Pseudoternary Compounds from the Bi2O3–TiO2–TeO2 System

Using X-ray diffraction analysis, scanning electron microscopy, thermogravimetry, and measurements of the dielectric properties up to the MW frequency range, the characterization of Bi₂Ti₃TeO₁₂, Bi₂TiTeO₈, and Bi₆Ti₅TeO₂₂ compounds, which all include Te⁶⁺, was performed. As the processes of Te⁶⁺ reduction and the evaporation of TeO₂-containing species contribute to the presence of secondary phases, the preparation of single-phase ceramics is rather difficult. To minimize the amount of secondary phases during the firing process, the pellets were muffled in a corresponding compound and then fired in an autoclave furnace under 10 bars of oxygen pressure. By sintering the Bi₂Ti₃TeO₁₂, Bi₂TiTeO₈, and Bi₆Ti₅TeO₂₂ between 840° and 1010°C, ceramics with ɛ_r ranging from 36 to 350, Q × f values from 220 to 12 500 GHz, and τ_f from +41 to +2600 ppm/K were obtained.