Microwave dielectric properties of BaO–TeO2 binary compounds

A series of BaO-TeO2 binary ceramic compounds were explored for microwave dielectric applications with ultra-low processing temperatures. During the calcination of mixed BaCO3 and TeO2 raw powders, BaTe4O9, BaTe2O6, BaTeO3, and Ba2TeO5 phases were obtained through the sequential phase formations from Te-rich to Ba-rich phases at temperatures ranging from 500 to 850 deg C. Sintering temperatures were as low as only 550 deg C for the Te-rich phases. Barium tellurate ceramics exhibited excellent microwave dielectric properties with intermediate dielectric permittivities and high quality factors (Q). The dielectric properties at microwave frequencies were e,= 10-21, Q xf= 34,000-55,000 GHz, and TCf=-51 to -124 ppm/ deg C, depending on compositions.