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Effect of Calcination Temperature on the Structural and Electrical Properties of Low-Temperature-Sintered (Na0.52K0.44Li0.04)(Nb0.88Sb0.08Ta0.04)O3 Ceramics
D.Y. Lv, Z. Liu, W.W. Jin, Z. Ye, F. Hua, K. Wu
Institute of Materials Science, Wuhu Institute of Technology, Wuhu, 241003, Anhui, P.R. China
received January 30, 2020, received in revised form July 29, 2020, accepted August 9, 2020
Vol. 11, No. 2, Pages 99-102 DOI: 10.4416/JCST2020_00011
Abstract
Low-temperature-sintered lead-free 1.5 mol%-Na2O-excess (Na0.52K0.44Li0.04)(Nb0.88Sb0.08Ta0.04)O3 (NKN-LST) ceramics were calcined at 500 ∼ 950 °C. At 500 °C, a perovskite structure of the calcined powders without crystallinity was obtained. As the calcination temperature increased, an orthogonal structure began to form. And at 750 °C, the NKN-LST powders have a single orthogonal structure. The NKN-LST powders form a tetragonal structure when the calcination temperature ≥ 800 °C. Therefore, in the calcination temperature range of 800 ∼ 900 °C, the NKN-LST powders have two orthogonal and tetragonal structures. However, it can be seen that a two-phase coexistence zone of orthogonal and tetragonal structure exists in all the ceramics sintered in air at 1 020 °C for 3 h. Moreover, with increasing calcination temperature, the tetragonal phase increases. There is also an increase in the abnormal grains with increasing the calcination temperature, which may be attributable to a decrease in the critical driving force. At the same time, it has been found that the composition and structure determine the properties of NKN-LST ceramics. The optimum electrical properties of NKN-LST ceramics with a d33 of 384 pC/N, a kp of 0.53, and an ε33T of 2 735, were obtained when the ceramics were calcined at 700 °C. These properties indicated that the ceramics studied have the potential to replace lead-based ceramics in device applications. Therefore, the reduction of the calcination temperature leads to a significant improvement of 1.5 mol%-Na2O-excess NKN-LST piezoelectric ceramics.
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Keywords
Lead-free piezoelectric ceramics, low-temperature sintering, calcination, electrical properties
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