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In this study, a series of (Ba 0.95 Ca 0.05 )(Ti 0.90 Sn 0.10 )O 3 – x LiF (BCTS– x LiF) (0≤ x ≤6 mol%) lead-free piezoceramics were fabricated by a conventional solid-state reaction method. The incorporation of LiF could significantly improve the sinterability of BCTS ceramics by reducing the sintering temperature from 1480 °C to 1250 °C, where a relative density over 90% was achieved with grown grains of 5–20 μm. X-ray diffraction and Raman spectroscopy experiments revealed that BCTS– x LiF ceramics are composed of coexisting R – O – T phases at 0≤ x ≤1 and R – T phases at 2≤ x ≤6 at room temperature. Optimal piezoelectric properties of d 33 =510 pC/N, k p =40.9%, ε r =5370, tan δ =0.019 and d S /d E =961 pm/V were obtained at x =5, which is attributed to the coexistence of R and T phases with an optimum ratio at room temperature and dense structure with large grains. [ABSTRACT FROM AUTHOR]

A high piezoelectricity enhancement achieved in (Ba,Ca)(Ti,Sn)O 3 lead-free ceramics sintered with 4 mol% Li 2 O additives by intensifying effect of sintering temperature ( T S ) in a wide interval (1300–1450 °C) has been found to be related to both the point defects and phase structures. X-ray photoelectron spectroscopy confirmed a reduction of tetravalent cations in B-sites to lower valence state such as Ti 3+ and Sn 2+ along with an increased content as raising T S . Photoluminescence spectra indicated higher oxygen vacancy concentrations as T S is too low or too high than those at an intermediate T S range, which is attributed to the volatilization of Li + and the inadequate oxygen supply in environment at high T S . Owing to coexisting rhombohedral and tetragonal phases at room temperature, a high piezoelectric coefficient d 33 up to 578 pC/N was achieved as T S =1350 °C. [ABSTRACT FROM AUTHOR]

This work investigated the enhanced sintering and electrical properties of (Ba 0.95 Ca 0.05 )(Ti 0.90 Sn 0.10 )O 3 - x Li 2 O (BCTSLi x , x = 0, 1, 2, 3, 4, 5 and 6 mol%) lead-free piezoelectric ceramics benefiting from the Li 2 O addition. Highly dense BCTS ceramics with good piezoelectric properties were fabricated at reduced sintering temperatures by adding a small amount of Li 2 O. It was found that the sintering densification is promoted mainly by reaction liquid phase at the early sintering stage and the formation of oxygen vacancies should be considered as an additional factor. The coexistence of R and T phases was confirmed by the Raman spectrum at a temperature range from−50 °C to 40 °C as x = 2 and at room temperature for all other Li 2 O added samples, while their specific ratio of R to T phase decreases with increasing Li 2 O addition. Better properties with d 33 = 457 pC/N, k p = 25.18% and Q m = 491 were obtained when adding 4 mol% Li 2 O, which are attributed dominantly to the appropriate specific ratio of R to T phase because of the similar grain size and density for samples at 3 ≤ x ≤ 6. [ABSTRACT FROM AUTHOR]

A series of Li2 CO3-added ( Ba0.95 Ca0.05)( Ti0.90 Sn0.10) O3 ( BCTS) ceramics were prepared by normal sintering at a low temperature of 1300°C; Their microstructure and electrical property evaluation were investigated with special emphases on the effect of Li2 CO3 addition. Adding Li2 CO3 significantly improves the sinterability of BCTS ceramics, resulting in a reduced sintering temperature by more than 150°C. The coexistence of R and T phases is confirmed by the Raman spectrum at room temperature for all samples and at a temperature range from −80°C to 40°C for sample with 3% mol Li2 CO3 addition. The specific ratio of R to T phase decreases with increasing temperature or Li2 CO3 addition. A higher εr is observed in T phase compared to R phase in the studied BCTS system. Better properties with d33 = 485 pC/N, kp = 39%, and Qm = 191 were obtained for BCTS sample with 3% mol Li2 CO3 addition, which is attributed to the increased grain size and density along with the variation in the specific ratio of R to T phase. [ABSTRACT FROM AUTHOR]

( Ba1− x Ca x)( Ti0.92 Sn0.08) O3 ( x = 0.00-0.06 mol) ceramics with a high relative density over 96% were prepared by a conventional sintering method at 1480°C. At room temperature, a polymorphic phase transition from orthorhombic phase to tetragonal phase was confirmed by the XRD patterns in the composition range of 0.04 ≤ x ≤ 0.06. A high piezoelectric coefficient d33 up to 568 pC/N was obtained at x = 0.05 mol, which is higher than the other component of ( Ba, Ca)( Ti, Sn) O3 system. At the same time, the corresponding planar electromechanical coupling factor kp, converse piezoelectric coefficient dS/ dE, and dielectric constant εr reach 47.7%, 1013 pm/V, and 23000, respectively. These results indicate that the ( Ba, Ca)( Ti, Sn) O3 ceramics are a promising candidate to replace for the lead-based piezoelectric materials. [ABSTRACT FROM AUTHOR]