Synthesis and effect of Ba2+ ions on the dielectric properties of the layered-perovskite KSr2NaNb4O13 ceramics. (September 2018)

• Record Type: Journal Article
• Authors: Im, Mir; Kim, Dong-Ha; Kweon, Sang-Hyo; Lee, Woong-Hee; Nahm, Sahn
• Is Part Of: Materials research bulletin. Volume 105(2018)
• Page Start: 246
• Page End: 252
• Publication Date: 2018-09
• Subjects: K(Sr2Na)Nb4O13 compound -- Layered perovskite -- Dion-Jacobson (DJ) phase -- Inorganic nanosheets -- High-κ dielectrics; Materials -- Periodicals; Crystal growth -- Periodicals; Matériaux -- Périodiques; Cristaux -- Croissance -- Périodiques; Crystal growth; Materials; Periodicals; 620.11
• DOI: 10.1016/j.materresbull.2018.04.056
• Languages: English
• ISSNs: 0025-5408

Abstract

Graphical abstract: Highlights: 25 mol% excess K2 O was added to densify the pure K(Sr2 Na)Nb4 O13 ceramic at 1275 °C. K(Sr2 Na)Nb4 O13 ceramic has an increased εr compared with that of KSr2 Nb3 O10 ceramic. K(Sr0.8 Ba0.2 )2 NaNb4 O13 ceramic has a highest εr of 67.4 with a small tan δ of 0.14. Large εr is explained by the increased dipole moment and NbO6 octahedron distortion. Abstract: The 25 mol% K2 O-added K(Sr2 Na)Nb4 O13 ceramic sintered at 1275 °C exhibited a pure and dense K(Sr2 Na)Nb4 O13 phase, which had four octahedral layers. Synthesis of a pure K(Sr2 Na)Nb4 O13 ceramic was not possible without excess K2 O, due to the formation of aNa-deficient K(Sr2 Na2 )Nb5 O16 secondary phase, because of K2 O evaporation during sintering. The dielectric constant ( εr ) of the K(Sr2 Na)Nb4 O13 ceramic was 43.8 at 100 kHz, two times higher compared to the KSr2 Nb3 O10 ceramic, which has three octahedral layers. The increased εr can be explained by the increased number of octahedral layers. Some of the Sr 2+ ions in K(Sr2 Na)Nb4 O13 ceramic were replaced by Ba 2+ ions, which have high ionic polarizability, to further increase εr . The 25 mol% K2 O-excess K(Sr0.8 Ba0.2 )2 NaNb4 O13 ceramic sintered at 1250 °C showed a high εr of 67.4 at 100 kHz, which can be explained by the increased dipole moments and distortion of the NbO6 octahedra.