Sintering Behaviour and Piezoelectric Properties of CuO-Added Lead-Free Bi(Na,K)TiO₃Ceramics

Abstract

Effect of excess CuO on the sintering behaviour and piezoelectric properties of Bi 0.5 (Na 82 K 0.18 ) 0.5 TiO 3 ceramics was investigated. The addition of small amount of excess CuO as low as 0.01 mol was quite effective to lower the sintering temperature (T s ) of BNKT ceramics down to 975 • C which is 200 • C lower than the T s of pure BNKT (1175 • C) without significant degradation of their piezoelectric properties. From microstructure analysis, it was concluded that CuO promotes sintering via forming a liquid phase at 975 • C and partly dissolves into Ti-sites during sintering.

Comparing the electromechanical properties of CaTiO3‐ and BaZrO3‐modified Bi0.5Na0.5TiO3–SrTiO3 ceramics

“…It is noted that the results are inconsistent with the present authors' predictions regarding the relationship between the tolerance factor and the ferroelectric-relaxor phase transition [13,28,29,30]. Thus, while the CT100x ceramics retain their ferroelectricity with decreasing t and do not undergo a phase transition within the investigated composition range (0-4 mol%), a rapid transition from ferroelectric to relaxor does occur in the BZ100y solid solutions.…”

“…Furthermore, a similarly large electric field-induced strain has been achieved in many BNT-based ceramics via elemental modification at the A-and/or B-sites, e.g., by the substitution of Fe and Nb into the B-site of BNT-BT [24], the substitution of Ta into BNKT [25], the co-doping of BNKT with Li/Nb [26], or Li-modification of the A-sites in BNKT-BT [27]. Interestingly, in previous work on the modification of BNKT with Nb [13], Cu [28], Sn [29], and Ta [30], the present researchers have found that the FE-RFE phase transition occurs when the dopant modifier leads to a decrease in the Goldschumidt's tolerance factor (t), which is given by the following equation [31]:…”

Current Development in Lead-FreeBi0.5(Na,K)0.5Quan1, Bac2, Thiet3 et al. 2014Advances in Materials Science and Engineering

“…However, theoretical calculation indicated that the ultrahigh electromechanical response in single-crystal piezoelectrics resulted from polarization rotation during poling processing [54]. Coupling factor, k p (%) [57] BNKT-(Li, Ce) [59] BNKT-(Li, La) [61] BNKT-Nd [58] BNKT-La [56] BNKT-Ce [63] BNKT-Gd [65] BNKT-Ho [66] BNKT-Er [67] BNKT-Eu [62] BNKT-Sm [84]. Moreover, this group also pointed out that the addition of La 2 O 3 /MnO to BNKAT-BT specimens displayed a very large strain dynamic constant max / max of 415 pm/V which results from the field-forced phase transition from the paraelectric phase to the ferroelectric phase [84].…”

Clarification on phase transition behaviors by local strain engineering in Bi1/2Na1/2TiO3–SrTiO3‐based ternary ceramics

“…However, the phase transition behaviors, more precisely phase transition from a nonergodic relaxor (NER) to ER, in those ternary systems are still unclarified, which may be complicated compared to binary systems. Interestingly, in previous work on the modification of BNKT with Nb, 27 Cu, 28 Sn, 29 and Ta, 30 the authors have investigated that the FE‐RFE phase transition occurs when the adding members lead to a decrease in the Goldschumidt tolerance factor ( t ), which is given by the following equation: $$$$\begin{equation}t = \frac{{{r}_{\rm{A}} + {r}_{\rm{O}}}}{{\sqrt 2 ({r}_{\rm{B}} + {r}_{\rm{O}})}}\end{equation}$$$$where r A , r B , and r O are the ionic radii of A‐ and B‐site cations, and oxygen, respectively.…”

“…However, the phase transition behaviors, more precisely phase transition from a nonergodic relaxor (NER) to ER, in those ternary systems are still unclarified, which may be complicated compared to binary systems. Interestingly, in previous work on the modification of BNKT with Nb, 27 Cu, 28 Sn, 29 and Ta, 30 the authors have investigated that the FE-RFE phase transition occurs when the adding members lead to a decrease in the Goldschumidt tolerance factor (t), which is given by the following equation:…”