Near-Zero Doped-Niobate Ceramics for Dielectric Resonator Applications

Of the niobate ceramics with the formula MNbO, several compounds (M = Zn, Mg, Ca and Co) are examined. values (at 1-10 GHz) are between 40 000 and 90 000 GHz, offering potential in dielectric resonator applications. However, their temperature coefficient of resonant frequency () values were too high for commercial development, at between −50 to −90 ppm. This paper details the doping of these materials with dielectric ceramics with a large positive , in an attempt to reduce the overall to zero, whilst maintaining a high quality factor (). Several materials have been made with near-zero , particularly 90% CoNbO / 10% CaTiO, which had = +2 ppm, = 21 700 GHz and = 25.