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

Journal Article · Sun Mar 01 00:00:00 EST 2009 · Journal of Applied Physics

DOI:https://doi.org/10.1063/1.3081643· OSTI ID:21190062

Yunfei, Chang; Zupei, Yang; Difei, Ma; Zonghuai, Liu; Zenglin, Wang ^[1]

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1. Key Laboratory for Macromolecular Science of Shaanxi Province, School of Chemistry and Materials Science, Shaanxi Normal University, Xi'an, 710062 Shaanxi (China)

(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.

• OSTI ID: 21190062
• Journal Information: Journal of Applied Physics, Vol. 105, Issue 5; Other Information: DOI: 10.1063/1.3081643; (c) 2009 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 0021-8979
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
CERAMICS
ELECTRIC CONDUCTIVITY
FERROELECTRIC MATERIALS
GRAIN GROWTH
LITHIUM COMPOUNDS
MICROSTRUCTURE
NIOBATES
ORTHORHOMBIC LATTICES
PERMITTIVITY
PHASE TRANSFORMATIONS
PIEZOELECTRICITY
POTASSIUM COMPOUNDS
RAMAN SPECTRA
SCATTERING
SINTERING
SODIUM COMPOUNDS
TANTALATES
TEMPERATURE RANGE 0273-0400 K