Effect of binary ion substitution on the crystal structure and microwave dielectric properties of MgTa₂O₆ ceramics

Abstract

Mg1/3A11/3A21/3Ta2O6 ceramics (where A1 and A2 represent Co, Ni, or Zn) were prepared using the solid‐phase reaction route. The results of X‐ray diffraction and Raman tests showed that (Co1/2Ni1/2)2+, (Co1/ 2Zn1/2)2+, and (Ni1/2Zn1/2)2+ ions replaced Mg2+ ions in the lattice of MgTa2O6, resulting in the formation of a pure tri‐rutile structure. All three complex ions could significantly reduce the sintering temperature of the ceramics (by 150°C–200°C) and could broaden the sintering window. The large deviation (48.8%–69.2%) between the porosity corrected relative permittivity εr‐corr. and the theoretical relative permittivity εr‐theo. might be due to the overestimation of the ionic polarizability of Ta5+ by Shannon. (Co1/2Ni1/2)2+ has the most significant effect of increasing the bond energy of ceramic A–O bonds, reducing the τf value from 51 to 36 ppm/°C. In addition, the mechanisms affecting their dielectric properties are discussed based on bond ionicity (fi), full width at half maximum (FWHM) of Raman peak, and bond energy (E). Mg1/3Co1/3Ni1/3Ta2O6 ceramic sintered at 1350°C have the most excellent microwave dielectric properties: εr = 26.8, Q × f = 86,000 GHz, and τf = 36 ppm/°C.