0.96(K0.49Na(0.51–x)Lix)(Nb0.97Ta0.03)O3–0.04Bi0.5Na0.5ZrO3无铅压电陶瓷的结构与电性能

Structure and Electrical Properties of 0.96(K_(0.49)Na_(0.51–x)Li_x)(Nb_(0.97)Ta_(0.03))O_3–0.04Bi_(0.5)Na_(0.5)ZrO_3 Lead-free Piezoelectric Ceramics

采用固相法制备0.96(K_(0.49)Na_(0.51–x)Li_x)(Nb_(0.97)Ta_(0.03))O_3–0.04Bi_(0.5)Na_(0.5)ZrO_3(0.96KNNTL_x–0.04BNZ,x=0.00,0.01,0.02,0.03,0.04)无铅压电陶瓷,研究Li掺杂量对0.96KNNTLx–0.04BNZ陶瓷相结构、微观形貌和电性能的影响。结果表明:0.96KNNTLx–0.04BNZ陶瓷为纯钙钛矿结构,随着Li掺杂量x的增加,陶瓷由正交–四方两相共存逐渐转变为四方相。在x≤0.01时,陶瓷为正交–四方两相共存的多型相转变(polymorphic phase transition,PPT)结构;当x≥0.02时,陶瓷转变为四方相结构。在PPT向四方相转变的组成边界(x=0.02)处,陶瓷具有优异的电性能:压电常数d33=335 p C/N,机电耦合系数kp=38.40%,机械品质因数Qm=43,介电常数εT33/ε0=1 350,介电损耗tanδ=2.70%,剩余极化强度Pr=23.50μC/cm2,矫顽场Ec=1.52 k V/mm,Curie温度TC=325℃。分析了组成x=0.02的陶瓷在不同温度和不同频率下的交流阻抗谱,表明晶粒和晶界对电传导机制共同起作用,介电弛豫激活能与高温下氧空位移动的激活能相吻合,Erelax=1.15 e V。

0.96（K_0.49Na_0.51-xLix）（Nb_0.97Ta_0.03）O3-0.04Bi_0.5Na_0.5ZrO3 （0.96KNNTLx-0.04BNZ, x=0.00, 0.01, 0.02, 0.03, 0.04） lead-free piezoelectric ceramics were prepared via a solid state reaction method. The effect of Li doping amount x on the crystal structure, micmstructure and electrical properties of the ceramics was investigated. The results indicate that all the samples possess a pure perovskite structure. The phase structure of the ceramics graduaUy changes from the coexisted orthorhombic and tetragonal phases to tetragonal phase when Li doping amount x increases. A polymorphic phase transition （PPT） structure with the coexisted orthorhombic and teWagonal phases appears when x≤0.01, while the structure is Wansformed to tetragonal phase when x≥0.02. The ceramics when x=O.02 on the compositional side from PPT to telragonal exhibit the optimal electrical properties i.e., piezoelectric coefficient d33 of 335 pC/N, planar electromechanical coupling kp of 38.40%, mechanical quality factor Qm of 43, dielectric permittivity er3/t0 of 1350, dielectric 10ss tarδ of 2.70%, remnant polarization Pr of 23.50 μC/cm2, coercive field Ec of 1.52 kV/mm, and the Curie temperature Tc of 325 ℃ as well. The complex impedance spectra of the ceramics when x=0.02 were measured at different temperatures and frequencies, and it is indicated that the conduction mechanism is referred to both the grains and the grain boundaries. The activation energy for dielectric relaxation calculated is 1.15 eV, which well coincides with the activation energy associated with the movement of the oxygen vacancy at a high temperature;