Abstract
In this Article, we investigated the dielectric properties of B-site Ga-doped K0.5Na0.5NbO3 (KNN) in air using AC impedance spectroscopy from room temperature to about 800 *C. Powder X-ray diffraction (PXRD) studies showed the formation of perovskite-type structure with orthorhombic symmetry, √2ap × 4a p×√2ap (where ap is perovskite-type lattice constant) for x ) 0.01, 0.1, and 0.13 members of Na0.5K0.5Nb1-xGaxO3. The PXRD result is similar to the parent KNN structure. AC impedance results showed mainly bulk contribution over the frequency range of 0.1 Hz to 1 MHz for the x ) 0.01 member, while bulk and grain-boundary contributions were present for x > 0.01 in the same frequency range. Scanning electron microscopy was used to study the effect of microstructure change for Ga3+ substitution in KNN. The inclusion of Ga3+ in KNN showed a significant change in the microstructure. The dielectric properties of Na0.5K0.5Nb1-xGaxO3 were enhanced by increasing the Ga3+ content; among the compounds studied, the x ) 0.1 member exhibited the highest dielectric constant and lowest dielectric loss at 1 MHz over the temperature range studied. All of the Na 0.5K0.5Nb1-xGaxO3 materials had a maximum dielectric constant at around 420 *C, which is consistent with other KNN ceramics reported in the literature and can be attributed to the Curie temperature. A small peak in the dielectric constant at around 220 *C was due to a structural phase transition.
Original language | English |
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Pages (from-to) | 4648-4653 |
Number of pages | 6 |
Journal | Journal of Physical Chemistry C |
Volume | 113 |
Issue number | 11 |
DOIs | |
Publication status | Published - 19 Mar 2009 |