1. Introduction
Bi0.5Na0.5TiO3 (BNT), discovered by Smolenskii et al.
[1] in 1960, is an ABO3 type ferroelectric with perovskite
phase. BNT is considered to be a promising candidate of
lead-free piezoelectric ceramics with a relatively large
remnant polarization (Pr¼38 mC/cm2
) and a high Curie
temperature (Tc¼320 1C) [1]. However, pure BNT ceramic
has high coercive field (Ec¼73 kV/cm), making the poling
of the ceramics extremely difficult. In addition, pure BNT
ceramic usually exhibits very poor piezoelectricity (d33¼58
pC/N). To decrease the coercive field and improve the
piezoelectric properties, a number of solid solutions of
BNT with ABO3-type ferroelectrics perovskite materials
such as BNT–Bi0.5K0.5TiO3 [2], BNT–BaTiO3–Bi0.5
K0.5TiO3 [3] and BNT–Bi0.5K0.5TiO3–BiFeO3 [4] have been
studied extensively. Among the solid solutions that have
been developed so far, (1xy)Bi0.5Na0.5TiO3–xBi0.5
K0.5TiO3–yBiFeO3 (BNKFT-x/y) system near rhombohedral–tetragonal
morphotropic phase boundary
(MPB) has attracted considerable attention. The MPB
compositions that showed remarkably superior electrical
properties existed in the range of 0.18rxr0.21 and
0ryr0.05. Zhou et al. [5] reported that the optimum
values of d33 and kp are 170 pC/N and 36.6%, obtained
from 0.79Bi0.5Na0.5TiO3–0.18Bi0.5K0.5TiO3–0.03BiFeO3
ceramics, respectively. Nevertheless, little is known about
the dielectric and piezoelectric properties and there is no
study on the ferroelectric properties.
Recently, in previous works we successfully fabricated
high quality oxide ceramics such as (Ba1xSrx)
(ZrxTi1x)O3 [6] by the combustion technique. The advantages
of this technique include inexpensive precursors and
simple preparation process, and result in good electrical
properties with low firing temperature and short dwelling
time [7]. Thus, in this work, BNKFT-x/y (0.12rxr0.24
and 0ryr0.07) ceramics were prepared by the combustion
method. The effects of sintering temperature and the
change of the x and y content on the phase formation,
microstructure, and electrical properties of ceramics were
investigated.
1. IntroductionBi0.5Na0.5TiO3 (BNT), discovered by Smolenskii et al.[1] in 1960, is an ABO3 type ferroelectric with perovskitephase. BNT is considered to be a promising candidate oflead-free piezoelectric ceramics with a relatively largeremnant polarization (Pr¼38 mC/cm2) and a high Curietemperature (Tc¼320 1C) [1]. However, pure BNT ceramichas high coercive field (Ec¼73 kV/cm), making the polingof the ceramics extremely difficult. In addition, pure BNTceramic usually exhibits very poor piezoelectricity (d33¼58pC/N). To decrease the coercive field and improve thepiezoelectric properties, a number of solid solutions ofBNT with ABO3-type ferroelectrics perovskite materialssuch as BNT–Bi0.5K0.5TiO3 [2], BNT–BaTiO3–Bi0.5K0.5TiO3 [3] and BNT–Bi0.5K0.5TiO3–BiFeO3 [4] have beenstudied extensively. Among the solid solutions that havebeen developed so far, (1xy)Bi0.5Na0.5TiO3–xBi0.5K0.5TiO3–yBiFeO3 (BNKFT-x/y) system near rhombohedral–tetragonalmorphotropic phase boundary(MPB) has attracted considerable attention. The MPBcompositions that showed remarkably superior electricalproperties existed in the range of 0.18rxr0.21 and0ryr0.05. Zhou et al. [5] reported that the optimumvalues of d33 and kp are 170 pC/N and 36.6%, obtainedfrom 0.79Bi0.5Na0.5TiO3–0.18Bi0.5K0.5TiO3–0.03BiFeO3ceramics, respectively. Nevertheless, little is known aboutthe dielectric and piezoelectric properties and there is nostudy on the ferroelectric properties.Recently, in previous works we successfully fabricatedhigh quality oxide ceramics such as (Ba1xSrx)(ZrxTi1x)O3 [6] by the combustion technique. The advantagesof this technique include inexpensive precursors andsimple preparation process, and result in good electricalproperties with low firing temperature and short dwellingtime [7]. Thus, in this work, BNKFT-x/y (0.12rxr0.24and 0ryr0.07) ceramics were prepared by the combustionmethod. The effects of sintering temperature and thechange of the x and y content on the phase formation,microstructure, and electrical properties of ceramics wereinvestigated.
การแปล กรุณารอสักครู่..
