Dielectric properties and microstructural characterization of cubic pyrochlored bismuth magnesium niobates
KAUST DepartmentPhysical Sciences and Engineering (PSE) Division
Materials Science and Engineering Program
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AbstractCubic bismuth pyrochlores in the Bi2O3 Bi 2O3-MgO-Nb2O5 Nb2O 5 system have been investigated as promising dielectric materials due to their high dielectric constant and low dielectric loss. Here, we report on the dielectric properties and microstructures of cubic pyrochlored Bi 1.5 MgNb 1.5 O 7 Bi1.5MgNb1.5O7 (BMN) ceramic samples synthesized via solid-state reactions. The dielectric constant (measured at 1 MHz) was measured to be ∼ 120 ∼120 at room temperature, and the dielectric loss was as low as 0.001. X-ray diffraction patterns demonstrated that the BMN samples had a cubic pyrochlored structure, which was also confirmed by selected area electron diffraction (SAED) patterns. Raman spectrum revealed more than six vibrational models predicted for the ideal pyrochlore structure, indicating additional atomic displacements of the A and O′ O' sites from the ideal atomic positions in the BMN samples. Structural modulations of the pyrochlore structure along the  and  directions were observed in SAED patterns and high-resolution transmission electron microscopy (HR-TEM) images. In addition, HR-TEM images also revealed that the grain boundaries (GBs) in the BMN samples were much clean, and no segregation or impure phase was observed forming at GBs. The high dielectric constants in the BMN samples were ascribed to the long-range ordered pyrochlore structures since the electric dipoles formed at the superstructural direction could be enhanced. The low dielectric loss was attributed to the existence of noncontaminated GBs in the BMN ceramics. © 2013 Springer-Verlag Berlin Heidelberg.
SponsorsThis work was supported in part by National Natural Science Foundation of China (Grant Nos. 10874065, 11174122, and 11134004), key projects from Ministry of Science and Technology of China (Grant Nos. 2009CB929503 and 2009ZX02101-4), and Analysis & Test Fund of Nanjing University. T. Al-Kassab acknowledges the generous support of the KAUST baseline funds.
PublisherSpringer Science + Business Media
JournalApplied Physics A