Dielectric properties of Na1−xKxNbO3, near x = 0.5 morphotropic phase region. (December 2018)

• Record Type: Journal Article
• Authors: Singh, Surendra; Negi, Jyotsana; Panwar, N.S.
• Is Part Of: Journal of physics and chemistry of solids. Volume 123(2018)
• Page Start: 311
• Page End: 317
• Publication Date: 2018-12
• Subjects: Ferroelectric -- Perovskite -- Dielectric properties -- Morphotropic phase transition; Solids -- Periodicals; Solides -- Périodiques; Solids; Periodicals; 530.41
• DOI: 10.1016/j.jpcs.2018.08.018
• Languages: English
• ISSNs: 0022-3697

Abstract

Abstract: Sodium-potassium niobate (Na1−x Kx NbO3 ) ceramic pellets, with x = 0.490, 0.495, 0.500, 0.505 and 0.510, were prepared by solid state reaction method with double sintering. With varying potassium content (x), dielectric properties and X-ray diffraction (XRD) peaks shifting pattern exhibit strong compositional dependence. Among the prepared compositions, a break in the XRD peaks shifting tendency, and minimum dielectric constant, loss tangent and Electric conductivity indicate a morphotropic phase transition type behavior, at the composition with x = 0.500. Highlights: Sodium-potassium niobate (Na1−xKxNbO3) ceramic pellets, with x = 0.490, 0.495, 0.500, 0.505 and 0.510, were prepared by solid state reaction method with double sintering. For the prepared compositions, generally, a < c, and slop of the plot of c/a ratio with x was found positive; except for the compositions 0.500 ≤ x ≤ 0.505, where a > c and slop of the plot of c/a ratio with composition was found negative, which indicates structural anomaly in this compositional region. The observed energy dispersive X-ray analysis (EDAX) results of the prepared samples. A significant escaping of alkali (Na and K) ions was observed in the sintered pellets, having lowest for the composition with x = 0.500. The observed composition (0.490 ≤ x ≤ 0.510) dependence of dielectric constant (ε), loss tangent (tan δ) and electric conductivity (σ) of Na1-xKxNbO3 ceramics, at room temperature (RT) and different frequencies. For all the prepared compositions, generally, ε and tan δ were observed decreasing and σ increasing, with increasing frequency. At 1 MHz, the observed composition (0.490 ≤ x ≤ 0.510) dependence of ε, tan δ and σ, at different temperatures. With increasing temperature, in the measured range, ε, tan δ and σ of all the prepared samples were found increasing. In the prepared Na1-xKxNbO3 (0.490 ≤ x ≤ 0.510) compositions, the p- type conductivity was found due to the excess of A- site vacancy concentration over the O- type vacancies.