Proposal of a rhombohedral-tetragonal phase composition for maximizing piezoelectricity of (K,Na)NbO3 ceramics

Abstract

Great progress in the field of piezoelectricity of (K,Na)NbO3 (KNN) lead-free ceramics, driven by emerging rhombohedral-tetragonal (R-T) phase boundary, has instigated research activity regarding elaborate controls of the phase boundary structure. Through phase-microstructure-property mapping in KNN ceramics doped with Bi-containing perovskite oxides, in this study we for the first time report the existence of a certain R-T phase boundary state by which to create maximum piezoelectric response in KNN systems. This phase boundary condition is usually comprised of approximately 15% R phase and 85% T phase, regardless of the choice of dopant material. Any deviation from this phase composition, either by inclusion of orthorhombic (O) phase or by enrichment of R phase, has a negative effect on the value of d33. These findings can provide useful guidance for chemical doping control associated with the type of phase boundary and the phase composition for advanced KNN-based materials.

Emerging new phase boundary in potassium sodium-niobate based ceramics

“…24,25 More importantly, other groups not only constructed the NPB successfully, but also achieved enhanced performance (including d 33 values and strain temperature stability). 73,86,212,[221][222][223][224][225][226][227][228] For example, Zhang et al successfully constructed the NPB and even obtained higher d 33 values (e.g., 512 pC N À1 ) than our previously reported ones (e.g., 419-450 pC N À1 ), using the same additives (e.g., Sb 5+ , (Bi 0.5 Na 0.5 )ZrO 3 and (Bi 0.5 Na 0.5 )HfO 3 ), as marked by the red dashed line. 45,54,68,69,104 [221][222][223]226,227 More interestingly, Zhai et al achieved an ultra-high d 33 value of 700 pC N À1 in highly textured KNN-3T ceramics.…”

“…73,86,212,[221][222][223][224][225][226][227][228] For example, Zhang et al successfully constructed the NPB and even obtained higher d 33 values (e.g., 512 pC N À1 ) than our previously reported ones (e.g., 419-450 pC N À1 ), using the same additives (e.g., Sb 5+ , (Bi 0.5 Na 0.5 )ZrO 3 and (Bi 0.5 Na 0.5 )HfO 3 ), as marked by the red dashed line. 45,54,68,69,104 [221][222][223]226,227 More interestingly, Zhai et al achieved an ultra-high d 33 value of 700 pC N À1 in highly textured KNN-3T ceramics. 86 Although the textured KNN-3T ceramics were reported to exhibit an R-O phase coexistence, the exact formula of 0.96(K 0.5 Na 0.5 )(Nb 0.965 Sb 0.035 )-0.01CaZrO 3 -0.03(Bi 0.5 K 0.5 )HfO 3 was highly similar to those possessing the NPB.…”

Grain Growth Behavior and Electrical Properties of 0.96(K0.46−xNa0.54−x)Nb0.95Sb0.05O3–0.04Bi0.5(Na0.82K0.18)0.5ZrO3 Ceramics

“…Furthermore, as x increased, both the R-T transition temperature (T R-T ) and Curie temperature (T C ) shifted toward lower temperatures ( Figure 4 c), which supports the results in Table 1 . The piezoelectric properties of the R-T phase coexistence compositions are maximized when the fraction of the tetragonal phase is approximately 80% [ 38 , 39 ]. The deterioration of the piezoelectric properties of the x = 0.010 and 0.015 specimens observed in Figure 3 might be due to the high tetragonal phase fraction of more than 90%.…”

Strain Tunable Quantum Spin Hall Insulating Phase in Halogen‐Decorated Double‐Layer Stanene

“…[16] Then, the search for large bandgap TIs has been expanded to the bilayers/multilayers of these elements and their topological properties predicted theoretically. Bilayer of graphene has been most extensively studied, [17][18][19][20][21] along with silicene, [22][23][24] germanene, [25][26][27] and stanene [28,29] bilayers. A few layers of germanene [30] and stanene [31] have been reported to be grown experimentally and their structural and electrical properties have been characterized.…”