Fundamental Issues in the Synthesis of Ferroelectric Na0.5K0.5NbO3 Thin Films by Sol-Gel Processing

0357037 - ÚACH 2011 RIV US eng J - Journal Article
Chowdhury, A. - Bould, Jonathan - Londesborough, Michael Geoffrey Stephen - Milne, S.J.
Fundamental Issues in the Synthesis of Ferroelectric Na0.5K0.5NbO3 Thin Films by Sol-Gel Processing.
Chemistry of Materials. Roč. 22, č. 13 (2010), s. 3862-3874. ISSN 0897-4756. E-ISSN 1520-5002
Institutional research plan: CEZ:AV0Z40320502
Keywords : sodium-potassium niobate * pulsed-laser deposition * lead-free piezoceramics
Subject RIV: CA - Inorganic Chemistry
Impact factor: 6.400, year: 2010

In contrast to films fabricated by physical vapor deposition methods, thin films of Na0.5K0.5NbO3 (NKN) made by metal alkoxide sal gel routes generally fail to exhibit polarization-electric field responses typical of a ferroelectric. This study sets out to investigate the reasons for the problems in producing sol gel NKN films by examining the thermochemistry of the gel to ceramic conversion. The NKN precursor gels displayed multiple heating DTA crystallization exotherms in the temperature range 480-550 degrees C, which are attributed to compositional segregation of NKN components. At higher temperatures, 800-850 degrees C, a heating DTA endotherm and cooling DTA exotherm are indicative of melting and recrystallization of sodium/potassium carbonate secondary phases. Additionally, repeated thermal analyses, after storage of the gel decomposition product under ambient conditions, revealed a tendency for hydration and carbonation on exposure to air.
Permanent Link: http://hdl.handle.net/11104/0195409