Cation Ordering and Domain Boundaries in Ca[(Mg1/3Ta2/3)1− xTi x]O3 Microwave Dielectric Ceramics.

Cation ordering and domain boundaries in perovskite Ca[(Mg1/3Ta2/3)1− xTi x]O3 ( x=0.1, 0.2, 0.3) microwave dielectric ceramics were investigated by high-resolution transmission electron microscopy (HRTEM) and Rietveld analysis. The variation of ordering structure with Ti substitution was revealed together with the formation mechanism of ordering domains. When x=0.1, the ceramics were composed of 1:2 and 1:1 ordered domains and a disordered matrix. The 1:2 cation ordering could still exist until x=0.2 but the 1:1 ordering disappeared. Neither 1:2 nor 1:1 cation ordering could exist at x=0.3. The space charge model was used to explain the cation ordering change from 1:2 to 1:1 and then to disorder. A comparison between the space charge model and random layer model was also conducted. HRTEM observations showed an antiphase boundary inclined to the (111) c plane with a projected displacement vector in the 〈001〉 c direction and ferroelastic domain boundaries parallel to the 〈100〉 c direction. [ABSTRACT FROM AUTHOR]