“…The KNNS-BNZ ceramics used in this study show a quite large d 33 value of 535 pC/N at room temperature and a mass density ρ of 4.548 g/cm 3 , which corresponds to a relative density ρ′ of approximately 98.7% 36 . Therefore, these KNNS-BNZ ceramics might be taken as a good representative of those high- d 33 KNN-based piezoelectric ceramics obtained in recent years.…”
Section: Resultsmentioning
confidence: 87%
“…Compared to those prepared under shorter sintering time 35 , the present KNNS-BNZ ceramics shows a slightly lower T O-T but a little larger ρ′ and a further enhanced d 33 . The X-ray diffraction (XRD) analysis indicated that poled KNNS-BNZ ceramics at room temperature are in O–T phase coexistence with the phase volume ratios of V O = 54.2% and V T = 45.8%, respectively 36 . Figure 1 The ε′ vs. temperature dependence of poled KNNS-BNZ ceramic, which was measured upon heating.…”
Section: Resultsmentioning
confidence: 99%
“…The 0.96(K 0.48 Na 0.52 )(Nb 0.96 Sb 0.04 )O 3 –0.04(Bi 0.50 Na 0.50 )ZrO 3 (hereinafter denoted as KNNS-BNZ) ceramics were prepared via the conventional solid-state reaction route as per previous studies 36 . Starting raw materials of reagent-pure carbonate and oxide powders were precisely weighed in desired stoichiometric ratio and ball-milled in nylon jars with alcohol as medium.…”
Section: Methodsmentioning
confidence: 99%
“…Ideally, the specimen preparation that does not alter the frozen-in state is required so that the observed domain patterns can represent the frozen-in domain configurations of grains inside the ceramic 31 . For the reasons just described, the author’s group paid continuously their study efforts onto the domain structure of poled KNN-based ceramics by means of the acid-etching in the past few years 32 – 36 .…”
Domain structure often greatly affects piezoelectric performance of a ferroelectric ceramic. Accordingly, a convenient method that can well characterize the domain structure at various temperatures is highly desired for understanding the underlying mechanism. An improved acid-etching technique was recently developed for such purpose. Domain structure of poled 0.96(K0.48Na0.52)(Nb0.96Sb0.04)O3–0.04(Bi0.50Na0.50)ZrO3 ceramics with a large piezoelectric coefficient d33 of 535 pC/N was systematically investigated at three typical temperatures. It was found that domain configurations change significantly with temperature. Hierarchical nanodomain structure is widely observed in domain patterns acid-etched at 25 °C, due to the orthorhombic-tetragonal phase coexistence. By contrast, the majority part of those acid-etched at − 60 °C are simply some long parallel stripes, while a small amount of banded structure appears in broad stripes inside some grains. A nearly 63° intersectional angle is seen between two adjacent sets of parallel stripes in the domain pattern of a cuboid-shaped grain, indicating that orthorhombic phase remains down to − 60 °C. The domain patterns acid-etched at 80 °C become even simpler, mainly consisting of long parallel stripes that are several hundred nanometers wide and have quite straight edges. Fundamental issues associating with the possible domain configurations and the acid-etching were discussed on the simple mathematical basis.
“…The KNNS-BNZ ceramics used in this study show a quite large d 33 value of 535 pC/N at room temperature and a mass density ρ of 4.548 g/cm 3 , which corresponds to a relative density ρ′ of approximately 98.7% 36 . Therefore, these KNNS-BNZ ceramics might be taken as a good representative of those high- d 33 KNN-based piezoelectric ceramics obtained in recent years.…”
Section: Resultsmentioning
confidence: 87%
“…Compared to those prepared under shorter sintering time 35 , the present KNNS-BNZ ceramics shows a slightly lower T O-T but a little larger ρ′ and a further enhanced d 33 . The X-ray diffraction (XRD) analysis indicated that poled KNNS-BNZ ceramics at room temperature are in O–T phase coexistence with the phase volume ratios of V O = 54.2% and V T = 45.8%, respectively 36 . Figure 1 The ε′ vs. temperature dependence of poled KNNS-BNZ ceramic, which was measured upon heating.…”
Section: Resultsmentioning
confidence: 99%
“…The 0.96(K 0.48 Na 0.52 )(Nb 0.96 Sb 0.04 )O 3 –0.04(Bi 0.50 Na 0.50 )ZrO 3 (hereinafter denoted as KNNS-BNZ) ceramics were prepared via the conventional solid-state reaction route as per previous studies 36 . Starting raw materials of reagent-pure carbonate and oxide powders were precisely weighed in desired stoichiometric ratio and ball-milled in nylon jars with alcohol as medium.…”
Section: Methodsmentioning
confidence: 99%
“…Ideally, the specimen preparation that does not alter the frozen-in state is required so that the observed domain patterns can represent the frozen-in domain configurations of grains inside the ceramic 31 . For the reasons just described, the author’s group paid continuously their study efforts onto the domain structure of poled KNN-based ceramics by means of the acid-etching in the past few years 32 – 36 .…”
Domain structure often greatly affects piezoelectric performance of a ferroelectric ceramic. Accordingly, a convenient method that can well characterize the domain structure at various temperatures is highly desired for understanding the underlying mechanism. An improved acid-etching technique was recently developed for such purpose. Domain structure of poled 0.96(K0.48Na0.52)(Nb0.96Sb0.04)O3–0.04(Bi0.50Na0.50)ZrO3 ceramics with a large piezoelectric coefficient d33 of 535 pC/N was systematically investigated at three typical temperatures. It was found that domain configurations change significantly with temperature. Hierarchical nanodomain structure is widely observed in domain patterns acid-etched at 25 °C, due to the orthorhombic-tetragonal phase coexistence. By contrast, the majority part of those acid-etched at − 60 °C are simply some long parallel stripes, while a small amount of banded structure appears in broad stripes inside some grains. A nearly 63° intersectional angle is seen between two adjacent sets of parallel stripes in the domain pattern of a cuboid-shaped grain, indicating that orthorhombic phase remains down to − 60 °C. The domain patterns acid-etched at 80 °C become even simpler, mainly consisting of long parallel stripes that are several hundred nanometers wide and have quite straight edges. Fundamental issues associating with the possible domain configurations and the acid-etching were discussed on the simple mathematical basis.
“…For the sintering process, the temperature was increased suddenly to 1180 • C, maintained for 5 min, then cooled down for 5 min to 1070 • C and kept for 20 h to cool down further. Through these methods, the densification of the ceramics can be performed [15]. Figure 4 presents the kp of the specimen with x. Electro mechanical coupling factor kp ensures the efficient conversion of electrical energy into mechanical energy.…”
In this paper, (Na,K)1−xLi.x(Nb,Sb)O3–(Bi,Na)(Sr)ZrO3–BaZrO3 ceramics were fabricated with x(= Li) substitution by two-step sintering method, and their physical characteristics were investigated. When Li substitution was added to the ceramics, piezoelectric constant (d33) and electromechanical coupling factor (kp) were rapidly reduced. However, mechanical quality factor (Qm) was enhanced. For the KNN-BNZ((K,Na)(Nb)O3–(Bi,Na)(Sr)ZrO3) ceramics with Li(x) = 0 substitution, the best physical properties of d33 = 300 [pC/N], kp = 0.40, Qm = 33 and dialectic constant (εr) = 2430 were shown, respectively. Additionally, the KNN-BNZ ceramics with Li(x) = 0.02, the d33 of 246[pC/N], the kp of 0.37, the Qm of 42 and the εr of 2090 appeared, which were suitable for the low-loss piezoelectric actuator.
The past two decades have seen a great enhancement of piezoelectric coefficients (d33) to higher than 570 pC/N in (K, Na)NbO3 (KNN) piezoelectrics, but one notoriously unresolved issue is their severe temperature instability, obstructing them toward practical applications. The present work demonstrates a facile approach to overcome this problem by introducing a layered distribution of key dopants (Li and Sb) in a monolithic ceramic, featuring stepwise varied polymorphic phase transition (PPT) temperatures along the thickness direction. The dopant‐graded ceramic exhibits an outstanding d33 of 508 pC/N and a very large piezoelectric strain (Suni, of 0.18%). More importantly, an excellent temperature stability (d33 variation within 13% over the temperature range of 25–150 °C) is achieved, which is superior to that of most state‐of‐art KNN counterparts. These are attributed to the construction of spatially diffused PPT in combination with enhanced polarization, permittivity, and piezoresponse through interfacial effect, including the Maxwell–Wagner effect and intergranular stress by gradient doping. The results offer an alternative strategy for designing high‐performance piezoelectric materials with desirable temperature reliability.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
