Composition‐ and Temperature‐Dependent Large Strain in (1−x)(0.8Bi_0.5Na_0.5TiO₃–0.2Bi_0.5K_0.5TiO₃)– xNaNbO₃ Ceramics

Abstract

Ternary solid solutions of (1 -x)(0.8Bi 0.5 Na 0.5 TiO 3 -0.2Bi 0.5 K 0.5 TiO 3 )-xNaNbO 3 (BNKT-xNN) lead-free piezoceramics were fabricated using a conventional solid-state reaction method. Pure BNKT composition exhibited an electric-fieldinduced irreversible structural transition from pseudocubic to ferroelectric rhombohedral phase at room temperature. Accompanied with the ferroelectric-to-relaxor temperature T F-R shifted down below room temperature as the substitution of NN, a compositionally induced nonergodic-to-ergodic relaxor transition was presented, which featured the pinched-shape polarization and sprout-shape strain hysteresis loops. A strain value of~0.445% (under a driving field of 55 kV/cm) with large normalized strain of~810 pm/V was obtained for the composition of BNKT-0.04NN, and the large strain was attributed to the reversible electric-field-induced transition between ergodic relaxor and ferroelectric phase.

Large piezoelectric strain with ultra-low strain hysteresis in highly c-axis oriented Pb(Zr0.52Ti0.48)O3 films with columnar growth on amorphous glass substrates

“…6a also indicates that the piezoelectric strain value as high as 0.375% under low electric field of 55 kV/cm is obtained in the 4-µm-thick PZT film. This value is comparable with the superior strain in lead-free materials, such as NaNbO 3 -doped Bi 0.5 Na 0.5 TiO 3 –Bi 0.5 K 0.5 TiO 3 (0.445%) 12 , 0.965K 0.45 Na 0.55 Nb 0.98 Sb 0.02 O 3 –0.035Bi 0.5 Na 0.5 Zr 0.85 Hf 0.15 O 3 (0.325%) 32 , but in the bulk ceramic form. Further the piezoelectric coefficient of 690 pm/V in the 4-µm-thick PZT film is also equivalent to that in the lead-free (Bi 0.5 Na 0.5 )TiO 3 –BaTiO 3 (BNT-based) and (Ba,Ca)(Zr,Ti)O 3 ceramics 33 .…”

“…Similar high values ( S  = 0.23% at E max  = 50 kV/cm) were obtained in the (lead containing) Pb(Yb 0.5 Nb 0.5 )O 3 -PbHfO 3 -PbTiO 3 composition 10 . Recently very high strains have been observed in (Fe-Sb)-codoped (Bi 0.5 Na 0.5 ) 1−x Ba x Ti 0.98 O 3 (BNT–BT) ceramics ( S  = 0.57%,  = 713 pm/V at E max  = 80 kV/cm) 11 and in NaNbO 3 -doped Bi 0.5 Na 0.5 TiO 3 –Bi 0.5 K 0.5 TiO 3 (BNT–BKT) ceramics ( S  = 0.445%,  = 810 pm/V at E max  = 55 kV/cm) 12 . However, the strain hysteresis ( H ) values of these ceramics were very high, such as H ≈70% for the (Fe-Sb)-codoped BNT–BT system 11 and H ≈60% for the NaNbO 3 -doped BNT–BKT system 12 .…”

“…Recently very high strains have been observed in (Fe-Sb)-codoped (Bi 0.5 Na 0.5 ) 1−x Ba x Ti 0.98 O 3 (BNT–BT) ceramics ( S  = 0.57%,  = 713 pm/V at E max  = 80 kV/cm) 11 and in NaNbO 3 -doped Bi 0.5 Na 0.5 TiO 3 –Bi 0.5 K 0.5 TiO 3 (BNT–BKT) ceramics ( S  = 0.445%,  = 810 pm/V at E max  = 55 kV/cm) 12 . However, the strain hysteresis ( H ) values of these ceramics were very high, such as H ≈70% for the (Fe-Sb)-codoped BNT–BT system 11 and H ≈60% for the NaNbO 3 -doped BNT–BKT system 12 . These results indicate that high values of strain in piezoelectric ceramics are often accompanied by large strain hysteresis, which limits the useful application in piezoelectric actuators.…”

Relaxor-normal ferroelectric phase transition and significantly enhanced electromechanical strain behavior in Bi(Ni1/2Ti1/2)O3–PbTiO3–Pb(Mg1/3Nb2/3)O3 ternary system close to the morphotropic phase boundary

“…A series of recent studies have demonstrated that the mechanism for such giant electrostrains could be attributed to a reversible phase transformation from a disordered relaxor state to a long-range ferroelectric ordered state driven by an external electric field [22][23][24][25]. Unfortunately, this kind of strain was usually found in a relatively narrow compositional window and simultaneously exhibited serious hysteresis (up to 60% for widely studied (Na 0.5 Bi 0.5 )TiO 3 -based relaxors [4,23,24]) and large temperature sensitivity [26,27]. It was known that the dielectric relaxor behavior can be tailored by chemical compositions because of A-site or B-site cations with different sizes and valences randomly distributed on equivalent crystallographic positions.…”

Electric‐field induced phase transition and fatigue behaviors of (Bi0.5+x/2Na0.5‐x/2)0.94Ba0.06Ti1‐xFexO3 ferroelectrics

“…However, increasing protection awareness for environmental safety has been driving the search for lead‐free piezoelectric materials over the past decades . The perovskite structured Bi 0.5 Na 0.5 TiO 3 ‐based (BNT) materials have drawn attention to desirable characteristics such as strong ferroelectric polarization and large field induced strain . The solid solutions with other lead‐free ferroelectric materials such as BaTiO 3 and K 1‐ x Na x NbO 3 are found to have potential in ferroelectric, high‐temperature capacitor, and giant energy storage applications …”