Dielectric properties of MgTi_1−x(Zn_1/3B_2/3)_xO₃ (B = Nb⁵⁺, Ta⁵⁺) ceramics at microwave frequencies

Abstract

Microwave dielectric properties of MgTi_1−x(Zn_1/3B_2/3)_xO₃ (B = Nb⁵⁺, Ta⁵⁺, 0.025 ≤ x ≤ 0.125) were investigated based on their structural characteristics and the electronegativity difference of the constituent ions. For the specimens of MgTi_1−x(Zn_1/3Nb_2/3)_xO₃, a single phase of the rhombohedral ilmenite structure appeared for the entire range of compositions (0.025 ≤ x ≤ 0.125), while MgTi_1−x(Zn_1/3Ta_2/3)_xO₃ showed a single phase of ilmenite structure up to x = 0.075, and then MgTi₂O₅ was detected as a secondary phase on further substitution of (Zn_1/3Ta_2/3)⁴⁺ at Ti⁴⁺-site of MgTiO₃. Quality factor value increased with the electronegativity difference up to an electronegativity difference of 2.015 and was dependent on the degree of covalent character of the bond. Temperature coefficient of resonant frequency decreased with an increase in oxygen octahedral distortion. Dielectric constant of the specimens did not exhibit any remarkable change with the substitution of (Zn_1/3B_2/3)⁴⁺ at Ti⁴⁺-site of MgTiO₃.