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Microwave dielectric ceramics Ba(M1/32+M2/35+)O3 have been studied for many years, but the exact relations between the B-site ions and the ceramics’ dielectric properties are still unclear. We take 2:1-ordered Ba(Zn1/3Nb2/3)O3 (BZN) and Ba(Mg1/3Nb2/3)O3 (BMN) as examples and discuss their static permittivity and intrinsic loss based on first-principles calculation. The larger mode-effective charges and lower frequencies of the normal modes are found to be responsible for the larger permittivity in BZN, but further analysis indicates that the dipole interaction, which is strengthened by the covalent bonding among Zn, Nb, and O, is the origin of these phenomena. In fact, the measured loss is found to be very close to the intrinsic loss in both BZN and BMN; we conclude that the difference in the measured loss is mainly the reflection of the difference in the intrinsic loss which is caused by the difference in permittivity between BZN and BMN. Moreover, our calculation results are in good agreement with the experimental values, a characterization of the Raman spectra of BZN and BMN is suggested based on our results. [ABSTRACT FROM AUTHOR]

Microwave dielectric ceramics Ba(M1/32+M2/35+)O3 have been studied for many years, but the exact relations between the B-site ions and the ceramics’ dielectric properties are still unclear. We take 2:1-ordered Ba(Zn1/3Nb2/3)O3 (BZN) and Ba(Mg1/3Nb2/3)O3 (BMN) as examples and discuss their static permittivity and intrinsic loss based on first-principles calculation. The larger mode-effective charges and lower frequencies of the normal modes are found to be responsible for the larger permittivity in BZN, but further analysis indicates that the dipole interaction, which is strengthened by the covalent bonding among Zn, Nb, and O, is the origin of these phenomena. In fact, the measured loss is found to be very close to the intrinsic loss in both BZN and BMN; we conclude that the difference in the measured loss is mainly the reflection of the difference in the intrinsic loss which is caused by the difference in permittivity between BZN and BMN. Moreover, our calculation results are in good agreement with the experimental values, a characterization of the Raman spectra of BZN and BMN is suggested based on our results. [ABSTRACT FROM AUTHOR]

Abstract: This paper discusses the difference in permittivity at infrared frequencies between Ba(Mg1/3Ta2/3)O3 (BMT) and Ba(Mg1/3Nb2/3)O3 (BMN) based on a first-principles calculation. The permittivity, far-infrared and Raman spectra are successfully computed. Analysis of these results shows that the smaller amplitude of O in the low frequency mode Eu 2 (BMT), which is caused by the larger polarizability of Ta5+, is the origin of the smaller permittivity of BMT. [Copyright &y& Elsevier]