Effects of B₂O₃doping on the dielectric and piezoelectric properties of (K,Na,Li)NbO₃–BaZrO₃–(Bi,Na)TiO₃ceramics

Abstract

(K,Na,Li)NbO3-BaZrO3-(Bi,Na)TiO3-x B2O3 (abbreviated as KNLN-BZ-BNT-x B2O3) ceramics were prepared by conventional solid state reaction method. The effects of B2O3 content on dielectric and piezoelectric properties of the KNLN-BZ-BNT ceramics have been studied. Based on the identification by X-ray diffraction (XRD), all the samples show a two-phase coexistence zone consisting of rhombohedral (R) and tetragonal (T) phases. For the ceramics with x = 0.5 wt%, the sintering temperature was observed to reduce from 1200 oC to 940 oC, while the samples maintained a high relative density around 97%. Because of the high densification and large grain size, the dielectric and piezoelectric properties were improved. As a result, the ceramics with x = 0.5 wt% sintered at 940 oC exhibited good properties of d 33 = 197 pC/N, k p= 0.29, tan δ = 0.029 and ε r = 1889, together with a Curie temperature (T C) of 222 oC.

The Sintering Aids Maintain Giant Strain in Lead‐Free NBT–ST Piezoceramics Sintered at 975 °C

“…The Li 2 CO 3 or B 2 O 3 addition increases the sinterability of NBT-based piezoelectric ceramics in various studies. [14][15][16][17]19,20] The liquid Li 2 CO 3 phase in doped 100xLB ceramics may cause sinterability enhancement. [19,20] The crystal structures of undoped 0LB/1175 °C and doped 100xLB/975 °C samples as a function of LB content (x) are presented in Figure 3.…”

“…[21,22] Some reports on NBT-based piezoceramics show the decrease of the sintering temperature with the stability of the crystal structures by Li 2 CO 3 or B 2 O 3 doping. [14][15][16][17]19,20] As shown in Figure 3b, the (111) and ( 200) diffraction peaks of the 100xLB samples shift to a larger diffraction angle while their full with at half maximum is increased as a function of LB content. It means that the addition of sintering aids increased the crystallite size of the 100xLB samples sintered at 975 °C.…”

“…Some cheap materials, such as Ag/Pd with a small amount of Pb, Ag/Pd/Cu, Ag/Pd/Ni, or Ag/Pd/Ni/Cu inner electrode, may be promising to reduce the multilayer piezoelectric actuators cost. [14,15] However, the low-cost multilayer piezoelectric actuators can only be stable if the sintering temperature is below 1000 °C.…”

“…The addition of B 2 O 3 sintering aids reduced the sintering temperature to 1075 °C in NBT-BT ceramics [14] and to 940 °C in NBT-(K,Na,Li)NbO 3 -BaZrO 3 ceramics. [15] The addition of B 2 O 3 can not only reduce the sintering temperature of the ceramics but also increase their piezoelectric properties, as seen in NBT-BT þ 1 wt%B 2 O 3 ceramic [14] or Ba(Zr 0.07 Ti 0.93 )O 3 þ 2 wt%B 2 O 3 ceramics. [16] In the previous studies on lead-free piezoceramics, the addition of synergistic sintering aids shows better sinterability with a better piezoelectric response than single sintering aids.…”

“…The addition of B 2 O 3 sintering aids reduced the sintering temperature to 1075 °C in NBT–BT ceramics [ 14 ] and to 940 °C in NBT–(K,Na,Li)NbO 3 –BaZrO 3 ceramics. [ 15 ] The addition of B 2 O 3 can not only reduce the sintering temperature of the ceramics but also increase their piezoelectric properties, as seen in NBT–BT + 1 wt%B 2 O 3 ceramic [ 14 ] or Ba(Zr 0.07 Ti 0.93 )O 3 + 2 wt%B 2 O 3 ceramics. [ 16 ]…”