A new phase of Ba(Mg1/3Ta2/3)O3 has been obtained by calcination at 1400°C. It belongs to the cubic Pm3m with a = 4·08840 (4) A and the crystal structure has been found to be the ideal perovskite by the Rietveld method from powder X-ray diffraction data.

Janaswamy Srinivas

E. D. Dias

G. Sreenivasa Murthy

BARIUM COMPOUNDS

Calcination

Crystal Structure

MAGNESIUM COMPOUNDS

Phase Transitions

Tantalum compounds

X ray powder diffraction

Rietveld method

Perovskite

Fulltext

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IIT Madras

Crystal structure of Ba(Mg1/3Ta2/3)O3 calcinated at 1400°C

Bulletin of Materials Science

The Ba3ZnTa2O9 (BZT) and Ba3MgTa2O9 (BMT) ceramics, a family of A3B2+B5+2O9 complex perovskites, are extensively utilized in mobile based technologies due to their intrinsic high unloaded quality factor, high dielectric constant and a low (near-zero) resonant frequency temperature coefficient at microwave frequencies. The preparation conditions as well as size and nature of B cations have a profound effect on the final dielectric properties. In this article, we report the effect of Nb5+ at the Ta5+ site on the BMT structure prepared at four synthesis temperatures (1300, 1400, 1500 and 1600 °C). The analysis has been carried out using the Rietveld technique on the X-ray powder diffraction data. Results suggest that both the preparation temperatures and Nb5+ content have significant effect on the ordering of B cations in the Ba3Mg(Ta1-xNbx)2O9 solid solution. A disordered (cubic) structure is preferred by the 1300 °C compounds. The weight percentage of the ordered (trigonal) phase escalates, for a given composition, with increasing calcination temperature. A fully ordered trigonal arrangement exists only for x = 0.0 and 0.2 compounds calcined at 1600 °C, and the rest are biphasic (cubic and trigonal). The increase in the cubic fraction upon Nb5+ augmentation suggests that the solid solution leans more toward the disordered structural arrangement of B2+ and B5+ cations. © 2007 Elsevier Ltd. All rights reserved.

Materials Research Bulletin

Structure analysis on the Ba3Mg(Ta1-xNbx)2O9 ceramics: Coexistence of order and disorder

Structure analysis of polycrystalline BaMg1/3Ta 1/3Nb1/3O3 ceramics has been carried out using the Rietveld technique, wherein the B cations (Mg, Ta, and Nb) have the same occupancy with a size difference and charge imbalance. The compound has an ordered trigonal structure as well as a disordered cubic phase depending on the preparation temperature. The weight percentage of the ordered phase is found to increase with a rise in the calcination temperature. © Pleiades Publishing, Inc., 2006.

Crystallography Reports

Ordering in BaMg1/3Ta1/3Nb1/3O3 ceramics: An X-ray Rietveld analysis

Journal of the American Ceramic Society

Ba(Zn1/3Ta2/3)O3 Ceramics with Low Dielectric Loss at Microwave Frequencies

Inorganic Chemistry

Ordering in Compounds of the A(B'0.33Ta0.67)O3Type

The Journal of Physical Chemistry

ORDERING OF THE OCTAHEDRALLY COÖRDINATED CATION POSITION IN THE PEROVSKITE STRUCTURE

Journal	Bulletin of Materials Science
Publisher	Indian Acad of Sciences, Bangalore
ISSN	02504707
Open Access	Yes