Microwave dielectric properties of Ba8Ta6(Ni1 − xMx)O24 (M = Zn and Mg) ceramics

The influence of M (M = Zn and Mg) substitution for Ni on the microwave dielectric properties and the crystal structure of Ba8Ta6(Ni1 − xMx)O24 ceramics was investigated in this study. The Ba8Ta6(Ni1 − xZnx)O24 (BTNZ) solid solutions showed a single phase in the composition range of 0–1, whereas the limit of Ba8Ta6(Ni1 − xMgx)O24 (BTNM) solid solutions was approximately x = 0.75; the lattice parameters of both solid solutions increased linearly, depending on the composition x. Although the dielectric constants (ɛr) of BTNZ were almost constant over the whole composition range, those of BTNM slightly decreased from 27.8 to 24.3; the decrease in the dielectric constant of BTNM is due to the change in relative density of the sample. The quality factors (Q × f) of both solid solutions were improved by the M substitution for Ni; the maximum Q × f values of BTNZ and BTNM were 91729 and 93127 GHz, respectively. Moreover, the temperature coefficients of resonant frequency (τf) of BTNZ and BTNM varied from 33 to 40 ppm/°C and from 33 to 26 ppm/°C, respectively.