| Piezoelectric properties of (Na0.545K0.47+x)(Nb0.55Ta0.45)O3 ceramics synthesized at different calcination temperature |
| M. S. Kim |
| Changwon National University |
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Lead-based piezoelectric materials, such as lead zirconate titanate (PZT), lead lanthanum zirconate titanate (PLZT) and lead magnesium niobate (PMN) are widely used in filters, resonators, actuators and sensors because of their excellent piezoelectric properties. However, the legislations such as RoHS/WEEE (Restriction of Hazardous Substances / Waste Electrical and Electronic Equipment) demand for lead-free alternatives. Lead-free Na0.5K0.5NbO3 (NKN) based ceramics have been considered as one of the superior lead-free candidate materials to replaced lead-based PZT ceramics because of theirs excellent piezoelectric properties and high curie temperature. However, pure NKN has a poor piezoelectric coefficient and sinterability.[1] Recently, we have investigated that (Na0.545K0.47) (Nb0.55Ta0.45)O3 ceramic has high piezoelectric coefficient d33 = 333 pC/N. It has been reported that Na excess play an important role in enhancement of piezoelectric properties.[2]
During sintering process, due to volatile nature in NKN ceramics, Na and K ion create the alkali-ion vacancies due to their volatility. Furthermore, to retain the charge neutrality, the alkali vacancies make the oxygen vacancy which decrease sample density.[3]
In this work, A-site excessed (Na0.545K0.47+x)(Nb0.55Ta0.45)O3 (x = -0.01, -0.005, 0, 0.005, 0.01) ceramics were synthesized at various calcination temperatures using Na2CO3 and K2CO3 as A-site starting materials. It is worth to note that the melting points of Na2CO3 and K2CO3 are 851 and 891 oC, respectively, [4] which can make liquid phases at different temperatures. Calcination temperature effect on piezoelectric properties of the A-site excessed (Na0.545K0.47+x)(Nb0.55Ta0.45) along with microstructural changes will be discussed in details.
References:
[1] Li at el, J. Am. Ceram. Soc. 96[12], (2013) 3677-3696.
[2] Y. S. Sung et al, Appl. Phys. Lett., 101, 012902 (2012).
[3] N. M. Hagh et al, J. Electroceram. 18 (2007) 339-346
[4] P. Bomlai et al, J. Am. Ceram. Soc. 90[5], (2007), 1650-1655
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| Acknowledgements : This work was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by Ministry of Education, Science and Technology (MEST) (2011-0030058). |
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