Microstructure, electrical properties, and electric field‐induced phase transitions in NaNbO₃–LiTaO₃ lead‐free ceramics

Abstract

Lead-free ceramics (1-x)NaNbO 3 -xLiTaO 3 were synthesized by an ordinary solid-state reaction method. Rietveld analysis reveals that the crystal structure changes from one orthorhombic phase with Pbcm space group to another orthorhombic phase with P222 1 space group when increasing x. The morphotropic phase boundary between two different orthorhombic symmetries is formed at 0.14 < x < 0.18. Excess LiTaO 3 causes an abnormal grain growth behavior. The pure NaNbO 3 presents four current peaks in the I-E loop, indicating electric-field-induced transitions. A low LiTaO 3 doping induces ferroelectricity in the initially antiferroelectric (AFE) NaNbO 3 . Enhanced ferroelectricity is obtained at x ¼ 0.02-0.12. The addition of LiTaO 3 makes the ceramics undergo a transition from an antiferroelectricity dominant to a ferroelectricity dominant phase state. The optimum d 33 , k p , Q m , and P r values of 46 pC/N, 18.3%, 1333, and 27.1 mC cm À2 are obtained when x equals 0.12, and the ceramic exhibits good temperature stability because of its high T C . In 1949, Matthias grew sodium niobate (NaNbO 3 ) crystals and found them to be ferroelectric (FE) at room temperature [7], but then Vousden rejected the ferroelectric-

Dielectric and Pyroelectric Properties of Sodium Niobate Ceramics Containing Inclusions of Ferroelectric Q Phase

“…The obtained value of P r ≈ 8.5 μC cm −2 is sufficiently lower than the best values of P r ≈ 25–30 μC cm −2 reported for NaNbO 3 ceramics . However, there are many works where much smaller P r values ≈3–8 μC cm −2 were obtained for NaNbO 3 ceramics by studying either P ( E ) loops or by integrating the TSC curve . This large scatter in the P r values may be due to the different quality and grain size distribution of ceramics and the difference in their defect structure.…”

High power density NaNbO3-LiTaO3lead-free piezoelectric transformer in radial vibration modes

“…In general, copper oxide, or CuO, compounds are commonly used to enhance the Q m value in piezoelectric ceramics [11][12][13]. However, it should be noted that the 0.88NaNbO 3 -0.12LiTaO 3 composition ceramic without any acceptor doping possesses a high Q m value of 1333 according to our previous study [14].…”

“…In our previous work [14], we reported that 12 mol% LiTaO 3doped NaNbO 3 ceramics (0.88NN-0.12LT) sintered at 1310 °C possessed a high Q m , good temperature stability, and a high T C . In this study, we also prepared the samples by an ordinary ceramic technique using metal oxides and carbonate powders: Na 2 CO 3 (99.8%), Li 2 CO 3 (98%), Nb 2 O 5 (99.99%), and Ta 2 O 5 (99.99%).…”

High Piezoelectricity in Eco-Friendly NaNbO3-Based Ferroelectric Relaxor Ceramics via Phase and Domain Engineering

“…NaNbO 3 ceramics exhibit a ferroelectric phase with electric field and possess piezoelectric properties ( d 33 ∼ 20 pC/N). However, the antiferroelectric phase is prevalent at room temperature. − To realize the stable existence of the ferroelectric phase in NN-based ceramics, researchers introduced LiTaO 3 , BaTiO 3 , ,, and (K 0.5 Bi 0.5 )­TiO 3 , as the second component to obtain NN-based piezoelectric ceramics with a stable ferroelectric phase. Zeng et al.…”