Phase coexistence and high electrical properties in (K{sub x}Na{sub 0.96-x}Li{sub 0.04})(Nb{sub 0.85}Ta{sub 0.15})O{sub 3} piezoelectric ceramics

(K{sub x}Na{sub 0.96-x}Li{sub 0.04})(Nb{sub 0.85}Ta{sub 0.15})O{sub 3} lead-free piezoelectric ceramics were produced by conventional solid-state reaction method. The effects of K/Na ratio on the phase transitional behavior, Raman spectrum, microstructure, and dielectric, piezoelectric, and ferroele...

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Bibliographic Details
Published in:Journal of applied physics 2009-03, Vol.105 (5)
Main Authors: Chang Yunfei, Yang Zupei, Ma Difei, Liu Zonghuai, Wang Zenglin
Format: Article
Language:English
Subjects:
CERAMICS
ELECTRIC CONDUCTIVITY
FERROELECTRIC MATERIALS
GRAIN GROWTH
LITHIUM COMPOUNDS
MATERIALS SCIENCE
MICROSTRUCTURE
NIOBATES
ORTHORHOMBIC LATTICES
PERMITTIVITY
PHASE TRANSFORMATIONS
PIEZOELECTRICITY
POTASSIUM COMPOUNDS
RAMAN SPECTRA
SCATTERING
SINTERING
SODIUM COMPOUNDS
TANTALATES
TEMPERATURE RANGE 0273-0400 K
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Summary:(K{sub x}Na{sub 0.96-x}Li{sub 0.04})(Nb{sub 0.85}Ta{sub 0.15})O{sub 3} lead-free piezoelectric ceramics were produced by conventional solid-state reaction method. The effects of K/Na ratio on the phase transitional behavior, Raman spectrum, microstructure, and dielectric, piezoelectric, and ferroelectric properties of the ceramics have been investigated. The phase structure of the ceramics undergoes a transition from orthorhombic to tetragonal phase with increasing x. A double-degenerate symmetric O-Nb-O stretching vibration v{sub 1} and a triply degenerate symmetric O-Nb-O bending vibration v{sub 5} are detected as relatively strong scattering in the Raman spectra. The peak shifts of v{sub 5} and v{sub 1} modes all have a discontinuity with x between 0.42 and 0.46, which may suggest the coexistence of orthorhombic and tetragonal phases in this range. Properly modifying x reduces the sintering temperature, promotes the grain growth behavior, and improves the density of the ceramics. The polymorphic phase transition (at T{sub o-t}) is shifted to near room temperature by increasing x to 0.44 (K/Na ratio of about 0.85:1), and the coexistence of orthorhombic and tetragonal phases in the ceramics at x=0.44 results in the optimized electrical properties (d{sub 33}=291 pC/N, k{sub p}=0.54, {epsilon}{sub r}=1167, tan {delta}=0.018, T{sub o-t}=35 deg. C, T{sub C}=351 deg. C, P{sub r}=27.65 {mu}C/cm{sup 2}, and E{sub c}=8.63 kV/cm). The results show that the equal K/Na ratio is not an essential condition in obtaining optimized electrical properties in (K{sub x}Na{sub 0.96-x}Li{sub 0.04})(Nb{sub 0.85}Ta{sub 0.15})O{sub 3} ceramics.
ISSN:0021-8979
1089-7550
DOI:10.1063/1.3081643