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外文期刊>Journal of Applied Physics
>Phase coexistence and high electrical properties in (K_(x)Na_(0.96-x)Li_(0.04))X(Nb_(0.85)Ta_(0.15))O_(3) piezoelectric ceramics
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Phase coexistence and high electrical properties in (K_(x)Na_(0.96-x)Li_(0.04))X(Nb_(0.85)Ta_(0.15))O_(3) piezoelectric ceramics
(K_(x)Na_(0.96-x)Li_(0.04))(Nb_(0.85)Ta_(0.15))O_(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_(1) and a triply degenerate symmetric O-Nb-O bending vibration v_(5) are detected as relatively strong scattering in the Raman spectra. The peak shifts of v_(5) and v_(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_(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(velence)0.44 results in the optimized electrical properties (d_(33)velence291 pC/N, k_(p)velence0.54, (epsilon)_(r)velence1167, tan (delta)(velence)0.018, T_(o-t)velence35 deg C, T_(C)velence351 deg C, P_(r)velence27.65 (mu)C/cm~(2), and E_(c)velence8.63 kV/cm). The results show that the equal K/Na ratio is not an essential condition in obtaining optimized electrical properties in (K_(x)Na_(0.96-x)Li_(0.04))(Nb_(0.85)Ta_(0.15))O_(3) ceramics.
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Key Laboratory for Macromolecular Science of Shaanxi Province, School of Chemistry and Materials Science, Shaanxi Normal University, Xi'an, 710062 Shaanxi, People's Republic of China;
