Influence of Compensated Li Content on Microstructure, Crystalline Phase and Electrical Properties of NKN-based Lead-free Piezoelectric Ceramics

doi:10.3724/SP.J.1077.2012.00385

Abstract

Abstract:

High dense Li_0.05+_x(Na_0.535K_0.48)_0.95NbO₃(L_xNKN) lead-free piezoelectric ceramics with fine morphology were synthesised by conventional mixed-oxide method at 1000℃, and its microstructure, phase structure and electrical properties were investigated as a function of excessive Li addition. The results revealed that the excess Li content facilitated the sinterability and improved the piezoelectric properties for L_xNKN ceramics. A PPT bridging tetragonal and orthorhombic symmetry was found at x= 0.01-0.015 by using the X-ray diffraction patterns and the corresponding calculation of lattice parameters. Owing to such transitional behavior, the piezoelectric coefficient (d₃₃), electromechanical coupling coefficient (k_p), dielectric constant (ε_r) and remanent polarization (P_r) were enhanced to peak values, 282 pC/N, 44%, 942 and 27 μC/cm², respectively. Compared with LNKN ceramics, the variation in Curie temperature (T_c) by the compensation amount of Li was much smaller for L_xNKN ceramics. The reason is that the amount of Li that entered into crystal lattice is relatively rare for L_xNKN ceramics. The results provide a way to low-temperature sintering of LNKN-based lead-free piezoceramics with high performance.

Key words: traditional solid-phase sintering, lead-free piezoelectric ceramics, PPT, niobate-based

CLC Number:

TB34

LI Hai-Tao, ZHANG Bo-Ping, WEN Jiu-Ba, XU Rong-Hui, LI Qian. Influence of Compensated Li Content on Microstructure, Crystalline Phase and Electrical Properties of NKN-based Lead-free Piezoelectric Ceramics[J]. Journal of Inorganic Materials, 2012, 27(4): 385-389.

Figures/Tables 8

Fig. 1 SEM images of the thermally etched surface of the LxNKN ceramics

Fig. 2 Measured density and relative density of LxNKN ceramics

Fig. 3 XRD patterns in the 2θ range of 20°-60° (a) and 30°-33° (b) for the LxNKN ceramics

Fig. 4 Lattice parameters of LxNKN ceramics

Fig. 5 Temperature dependence of dielectric constant (εr) of LxNKN ceramics with x=0, 0.010, 0.015 and 0.020 at 10 kHz

Fig. 6 Piezoelectric coefficient (d33) and electromechanical coupling factors ( kP) (a), dielectric constant (ε r) and loss (tanδ) (b) of LxNKN ceramics

Fig. 7 P-E hysteresis loops of LxNKN ceramics

Fig. 8 The remanent polarization Pr and coercive field Ec of LxNKN ceramics

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