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Effect of potassium sodium niobate (KNN) substitution on the structural and electrical properties of Na 0.5 Bi 4.5 Ti 4 O 15 ceramics

2016; Institute of Physics; Volume: 49; Issue: 12 Linguagem: Inglês

10.1088/0022-3727/49/12/125101

1361-6463

Xiangping Jiang, Xingan Jiang, Chao Chen, Na Tu, Yunjing Chen, Ban-chao Zhang,

Microwave Dielectric Ceramics Synthesis

The structural and electrical properties of (1 − x)Na0.5Bi4.5Ti4O15-xK0.5Na0.5NbO3 (NBT-KNN-100x) (x = 0.00, 0.05, 0.10 and 0.15) ferroelectric ceramics have been studied. Effects of potassium sodium niobate (KNN) on the phase structure and distortion of TiO6 octahedra have been characterized by x-ray diffraction and Raman scattering techniques. Dielectric and ferroelectric measurements were also conducted. The weakened structural distortion accounted well for the lower Curie temperature (Tc) as KNN increases. Ferroelectric properties of KNN doped NBT ceramics are improved. The of NBT-KNN-10 ceramics is significantly increased up to 24 pC/N owing to the increase in Pr. The relaxation process and electrical conduction were studied in detail using complex impedance spectroscopy. The calculated relaxation follows Arrhenius behavior with two different activation energies below and above the Tc region implying different conduction mechanisms. The AC conductivity obeys the universal power law: . The closeness of activation energy values for DC conductivity, hopping conduction and relaxation below Tc confirms the transport originating from the oxygen vacancy related hopping mechanism. The exponent s is also studied to understand the associated conduction mechanisms at the different temperature regions, which can be ascribed to the correlated barrier hopping model in the ferroelectric state and the non-overlapping small polaron model in the paraelectric state, respectively.