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BNT‐based ferroelectric ceramics: Electrical properties modification by Ta 2 O 5 oxide addition
Author(s) -
Han Jihui,
Yin Jie,
Wu Jiagang
Publication year - 2020
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/jace.16752
Subject(s) - materials science , piezoelectricity , ferroelectricity , dielectric , tantalum , ceramic , piezoelectric coefficient , oxide , bismuth titanate , solid solution , bismuth , crystal structure , mineralogy , analytical chemistry (journal) , composite material , crystallography , metallurgy , chemistry , optoelectronics , chromatography
Due to their superior piezo‐responses (strain S > 0.3%), bismuth sodium titanate (BNT)‐based relaxor ferroelectrics have received much attention. Compared to other chemical elements, tantalum (Ta) doping provides superior electro‐strain for these ferroelectrics, while the effect of Ta 2 O 5 as oxide additive has been rarely reported. Herein, lead‐free piezoceramics of Bi 0.5 (Na 0.72 K 0.22 Li 0.06 ) 0.5 TiO 3 ‐ x Ta 2 O 5 (BNKLT‐ x Ta 2 O 5 , x = 0‐0.015) are synthesized. We study the effects of Ta 2 O 5 addition on the crystal structure, piezoelectric responses, dielectric properties, and ferroelectric properties of BNKLT ceramics. All of the ceramics exhibit a typical perovskite structure, and Ta 2 O 5 diffuses into the BNKLT lattice to form a uniform solid solution. The addition of Ta 2 O 5 can make the grains more regular and uniform, while excess Ta 2 O 5 result in finer grains. The undoped BNKLT ceramics show good ferroelectric and piezoelectric properties (remnant polarization P r = 22.5 μC/cm 2 and piezoelectric coefficient d 33 = 250 pC/N); however, the addition of Ta 2 O 5 leads to an clear degradation in d 33 and P r . Meanwhile, the addition of an appropriate Ta 2 O 5 amount leads to an increase in the electro‐strain, and the unipolar strain reaches 0.385% under 60 kV/cm for x = 0.003, together with a higher normalized strain ( d 33 * = S max / E max ) of 633 pm/V ( x = 0.003). The enhanced strain behaviors can be attributed to the coexistence of the ferroelectric and relaxor states, and an excellent electrostriction coefficient Q 33 ( Q 33 = S / P 2 ) value of 0.038 m 4 C −2 is obtained under 60 kV/cm for x = 0.003.