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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]

Abstract: The polymorphic phase transition (PPT) from tetragonal to orthorhombic symmetry was tailored in lead-free piezoelectric ceramics Li0.08(Na0.52+x K0.48)0.92NbO3 (LN0.52+x KN) by controlling excess Na content, which is opposite to the usually reported orthorhombic–tetragonal phase transition. The grain growth was accelerated by adding excess Na, resulting in an increased grain size from 2–3μm to 7–8μm and a bimodal grain size distribution for samples x=0.015–0.04. The optimized piezoelectric properties with, i.e. d 33=226pC/N and k p=36.8% were obtained in sample x=0.04 due to the PPT effect. The corresponding T C, P r, and E r were 468°C, 25.5μC/cm2 and 1.20kV/mm, respectively. [Copyright &y& Elsevier]