DocumentCode
1322614
Title
Phase diagram and structure-property relationships in the lead-free piezoelectric system: Na0.5K0.5NbO3-LiTaO3
Author
Skidmore, T.A. ; Comyn, T.P. ; Bell, Andrew J. ; Zhu, Feida ; Milne, S.J.
Author_Institution
Inst. for Mater. Res., Univ. of Leeds, Leeds, UK
Volume
58
Issue
9
fYear
2011
fDate
9/1/2011 12:00:00 AM
Firstpage
1819
Lastpage
1825
Abstract
A phase-diagram for the Na0.5K0.5NbO3-LiTaO3 solid solution series (NKN-LT) is presented for compositions ≤10 mol% LT, based on the combined results of temperature-variable X-ray powder diffraction and dielectric measurements. In addition to the reported orthorhombic and tetragonal polymorphs of NKN-LT, a monoclinic phase is revealed. Changes to electrical properties as a function of LT substitution are correlated to phase content. Increasing the LT content from 5 to 7 mol% LT led to improved temperature stability of piezoelectric properties because of the avoidance of the monoclinic-tetragonal polymorphic phase transition during thermal cycling (at >;25°C). For 7 mol% LT samples: d33 = 200 pC/N; Tc = 440°C; εr = 550 and tan δ = 0.02 (at 20°C). Modification of this composition by solid solution with BiScO3 led to a decrease in d33 values. Transmission electron microscopy of a sample of 0.95[0.93 NKN-0.07LT]-0.05BiScO3 indicated a core-shell grain structure which led to temperature-stable dielectric properties.
Keywords
X-ray diffraction; crystal microstructure; lithium compounds; phase diagrams; polymorphic transformations; potassium compounds; sodium compounds; transmission electron microscopy; LiTaO3 substitution; NKN-LT; Na0.5K0.5NbO3-LiTaO3; Na0.5K0.5NbO3-LiTaO3 solid solution series; X-ray powder diffraction; core-shell grain structure; d33 values; dielectric measurements; electrical properties; lead-free piezoelectric system; monoclinic phase; monoclinic-tetragonal polymorphic phase transition; orthorhombic polymorphs; phase diagram; structure-property relationships; temperature stability improvement; temperature-stable dielectric properties; tetragonal polymorphs; thermal cycling; transmission electron microscopy; Ceramics; Dielectric measurements; Solids; Temperature distribution; Temperature measurement; X-ray diffraction;
fLanguage
English
Journal_Title
Ultrasonics, Ferroelectrics, and Frequency Control, IEEE Transactions on
Publisher
ieee
ISSN
0885-3010
Type
jour
DOI
10.1109/TUFFC.2011.2019
Filename
6020850
Link To Document