Large strain under low driving field in lead‐free relaxor/ferroelectric composite ceramics

Abstract

0.75(Na 0.5 Bi 0.5 )TiO 3 -0.25SrTiO 3 lead-free incipient piezoceramic is a promising candidate for actuator applications due to their large reversible electromechanical strains at the relatively low driving field of 40 kV/cm. In order to further reduce the driving field of 0.75(Na 0.5 Bi 0.5 )TiO-0.25SrTiO 3 relaxor ceramic to meet the requirements for real actuators application, the relaxor/ferroelectric (RE/FE) 0-3 composite ceramics method was employed. The polarization and strain behaviors were examined as a function of the weight ratio of the relaxor/ferroelectric phases. It was found that 90 wt% 0.75(Na 0.5 Bi 0.5 )TiO 3 -0.25SrTiO 3 /10 wt% 0.96 (Na 0.84 K 0.16 ) 1/2 Bi 1/2 TiO 3 -0.04SrTiO 3 RE/FE 0-3 type composite samples provided a high unipolar strain of 0.25% and the corresponding large-signal piezoelectric coefficient, d * 33 of 833 pm/V at 30 kV/cm, which are 32% higher than the values of the pure 0.75(Na 0.5 Bi 0.5 )TiO 3 -0.25SrTiO 3 . The enhanced electric-field-induced strain at relatively lower field was attributed primarily to the reduction in the RE-FE phase transition electric field. It was also found that the RE/FE composite ceramics exhibited significantly reduced frequency dependence in the unipolar strain behavior at room temperature.

Large pyroelectricity via engineered ferroelectric‐relaxor phase boundary

“…Dielectric relaxation refers to a time delay or lag in the polarization response of the material when an electric field is applied, which is critically dependent on the structural characteristic 30 . It can be seen that a steep skip of dielectric constant with no frequency dispersion is observed around 72°C, which is generally ascribed to the transition from FE to ergodic relaxor and is defined as T F–R 31 , 32 . As the temperature rises, the maximum dielectric constant with frequency dispersion arrives at temperature T m .…”

“…30 It can be seen that a steep skip of dielectric constant with no frequency dispersion is observed around 72 • C, which is generally ascribed to the transition from FE to ergodic relaxor and is defined as T F-R . 31,32 As the temperature rises, the maximum dielectric constant with frequency dispersion arrives at temperature T m . For x = 0.15 ceramics, the frequency dependence of ε r and tanδ are enhanced, the two dielectric anomalies moved to low temperature, especially, the T F-R moves to room temperature, indicating the coexistence of FE-and ergodic-relaxor phase around room temperature.…”

Large electrostrain in low‐temperature sintered NBT‐BT‐0.025FN incipient piezoceramics

“…Lead‐based piezoelectric ceramics, mainly Pb(Zr,Ti)O 3 (PZT), have been widely applied in various electronic devices due to their low‐cost processing and excellent piezoelectric properties . Nevertheless, lead‐free piezoelectric ceramics, including (K,Na)NbO 3 (KNN), BaTiO 3 (BT), and Na 0.5 Bi 0.5 TiO 3 (NBT)‐based materials, are fast becoming a key research topic in replacing conventional lead‐based materials due to serious concerns of highly toxic Pb/PbO‐based compound to human beings and environment . Among them, electroceramics with NBT‐based ceramics, for example, Na 0.5 Bi 0.5 TiO 3 ‐SrTiO 3 (NBT‐ST), Na 0.5 Bi 0.5 TiO 3 ‐K 0.5 Bi 0.5 TiO 3 (NBT‐KBT), Na 0.5 Bi 0.5 TiO 3 ‐BaTiO 3 (NBT‐BT), and Na 0.5 Bi 0.5 TiO 3 ‐Ba (Ti 0.95 Zr 0.05 )O 3 , are known as the most potential lead‐free candidate because of the excellent electrostrain .…”

“…[3][4][5][6][7] Nevertheless, lead-free piezoelectric ceramics, including (K,Na)NbO 3 (KNN), 8 BaTiO 3 (BT), 9 and Na 0.5 Bi 0.5 TiO 3 (NBT)-based materials, [10][11][12][13] are fast becoming a key research topic in replacing conventional leadbased materials due to serious concerns of highly toxic Pb/PbO-based compound to human beings and environment. [14][15][16][17][18] Among them, electroceramics with NBT-based ceramics, for example, Na 0.5 Bi 0.5 TiO 3 -SrTiO 3 (NBT-ST), Na 0.5 Bi 0.5 TiO 3 -K 0.5 Bi 0.5 TiO 3 (NBT-KBT), Na 0.5 Bi 0.5 TiO 3 -BaTiO 3 (NBT-BT), and Na 0.5 Bi 0.5 TiO 3 -Ba (Ti 0.95 Zr 0.05 ) O 3 , 19,20 are known as the most potential lead-free candidate because of the excellent electrostrain. [15][16][17][18] Multilayer actuators (MLAs) are widely applied in practical piezoelectric applications with co-fired ceramic and inner electrodes.…”

“…[14][15][16][17][18] Among them, electroceramics with NBT-based ceramics, for example, Na 0.5 Bi 0.5 TiO 3 -SrTiO 3 (NBT-ST), Na 0.5 Bi 0.5 TiO 3 -K 0.5 Bi 0.5 TiO 3 (NBT-KBT), Na 0.5 Bi 0.5 TiO 3 -BaTiO 3 (NBT-BT), and Na 0.5 Bi 0.5 TiO 3 -Ba (Ti 0.95 Zr 0.05 ) O 3 , 19,20 are known as the most potential lead-free candidate because of the excellent electrostrain. [15][16][17][18] Multilayer actuators (MLAs) are widely applied in practical piezoelectric applications with co-fired ceramic and inner electrodes. 21 Only expensive Pt or Ag/Pd inner electrodes are reported in NBT-based MLAs due to high sintering temperatures of NBT-based piezoelectric materials, which seriously restrict the wide application of NBT.…”