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Title: Microstructure and microchemistry of flash sintered K 0.5Na 0.5NbO 3

In this paper, flash sintering experiments were performed, for the first time, on sodium potassium niobate (KNN) ceramics. A theoretical density of 94% was achieved in 30 s under 250 V/cm electric-field at 990°C. These conditions are ~100°C lower and faster than the conventional sintering conditions. Grains tended to grow after 30 s. flash sintering duration under constant electric-field. Detailed microstructural and chemical investigations of the sample showed that there was inhomogenous Na, K distribution and it resembles a core–shell structure where K is more in the shell and Na is more in the core region. The inhomogenous distribution of Na and K was correlated with the doubling of the unit cell within the grain along 002 direction. Compositional equilibrium is achieved after a heat treatment at 1000°C for 4 h. Finally, the compositional variations appeared to have been linked to grain boundary melting during flash and consequent recrystallization as the sample cooled.
Authors:
 [1] ;  [1] ;  [2] ;  [3] ;  [4] ;  [4]
  1. Sabanci Univ., Istanbul (Turkey). Faculty of Engineering and Natural Sciences
  2. Brookhaven National Lab. (BNL), Upton, NY (United States). Center for Functional Nanomaterials
  3. Jozef Stefan Inst. (IJS), Ljubljana (Slovenia). Nanostructured Materials
  4. Univ. of Colorado, Boulder, CO (United States). Dept. of Mechanical Engineering
Publication Date:
Report Number(s):
BNL-113406-2017-JA
Journal ID: ISSN 1882-0743; R&D Project: 16060; 16060; KC0403020
Grant/Contract Number:
SC0012704; 1059B141300914
Type:
Accepted Manuscript
Journal Name:
Journal of the Ceramic Society of Japan
Additional Journal Information:
Journal Volume: 124; Journal Issue: 4; Journal ID: ISSN 1882-0743
Research Org:
Brookhaven National Lab. (BNL), Upton, NY (United States); Sabanci Univ., Istanbul (Turkey)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22); Scientific and Technological Research Council of Turkey (TUBITAK) (Turkey)
Contributing Orgs:
Jozef Stefan Inst. (IJS), Ljubljana (Slovenia); Univ. of Colorado, Boulder, CO (United States)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; Flash sintering; Ceramics; Center for Functional Nanomaterials; TEM: STEM-EDX; lead-free; core-shell
OSTI Identifier:
1341678