| Bismuth layer–structured ferroelectrics?BLSFs?encompasses many promising electrical properties,such as low aging rate,high Curie temperature and low dielectric loss,making BLSFs a kind of promising candidate for high temperature piezoelectric device.In this paper,the different BLSFs materials?m = 2,4,5?were synthesized,and the effects of ion substitution for BLSFs on their electrical properties were investigated.The results are summarized as follows:Lead–free piezoelectric ceramics,SrBi2Nb2O9?abbreviated as SBN,m = 2?,were prepared by conventional solid state reaction and the electrical properties of Sm3+,Mo6+ and complex ions(K0.5Bi0.5)2+ doping SBN ceramics were investigated.All the samples showed typical layered perovskite structure.The dielectric,ferroelectric and piezoelectric properties of the SBSN-x ceramics were investigated and found that the optimum electrical properties can be obtained at x=0.03,which are as follows: 2Pr = 14 ?C/cm2,d33 = 19 pC/N,Tc = 435 ?.The Mo ion is suggested to be a donor substitution to decrease the amount of oxygen vacancies,enhancing the ferroelectric and piezoelectric activity in the SBNM-x ceramics.The best electrical properties(e.g.,2Pr = 20.34 ?C/cm2,Tc = 458?,tan? = 0.495%,d33= 18 pC/N)are simultaneously obtained in the ceramics with x = 0.12.The grain size and the Curie temperature?Tc?of the SBN ceramics increased with the increase in(K0.5Bi0.5)2+ content.Excellent remanent polarization?2P/r = 15 ?C/cm2?was obtained for SKBN-0.2 ceramic.High piezoelectric coefficient(d33 = 21 pC/N)was obtained for SKBN-0.5.The ceramics exhibited optimum electrical properties at SKBN-0.2,2Pr = 15.5 ?C/cm2,d33 = 20 pC/N,Tc = 469?,?rd = 95.9%.Bismuth layer–structured ferroelectrics with formulas of Na0.5Bi4.5-xErxTi4O15?NBETx;x = 0.00,0.006,0.012,0.018 and 0.025?and Na0.5Bi4.5-x(La0.5Ce0.5)xTi4O15?NBT-LCx;x = 0.0,0.1,0.15,0.2 and 0.3?were synthesized by solid state reaction.The effect of Er3+ and complex ions(La0.5Ce0.5)3+ doping Na0.5Bi4.5Ti4O15?NBT,m = 4?ceramics on phase structure,microstructure and electrical properties were investigated.All the samples showed pure bismuth layered structure regardless of doping Er3+ or(La0.5Ce0.5)3+,and the lattice parameters a,b,and c varied with increasing ion substitution.The Tc of the NBET-x ceramics gradually increased because of the smaller ionic radius of Er3+ in comparison to that of Bi3+.The substitution of stable trivalent Er3+ for volatile Bi3+ was effective to increase the chemical stability of the perovskite layers and obtained excellent electrical properties.The NBET-x ceramics with x = 0.012 possess optimum electrical properties: 2Pr = 17.2 ?C/cm2,d33 = 21 pC/N,Tc = 658 ?.The replacement of Bi3+ by La3+ and Ce3+(or Ce4+),creating the donors,will is beneficial to the poling process,so as to significantly improve the piezoelectric properties.Thermal annealing studies indicated that the piezoelectric constant(d33)of NBT-LCx?x > 0?ceramics still keep up over 20 pC/N when annealing temperature increased to be 430?,suggesting the ceramics are the promising candidates for hightemperature applications.Sr1-x(K0.5Ce0.5)xNa0.5Bi4.5Ti5O18?KCSNBT-x,x = 0.0,0.1,0.2 and 0.3?lead-free piezoelectric ceramics were prepared by a conventional solid state method,and the effect of(K0.5Ce0.5)2+ modification in the A-site Sr2+ on their electrical properties was investigated.All the samples show typical bismuth layered structure,whereas the lattice parameters varied with increasing(K0.5Ce0.5)2+ substitution.The effect of(K0.5Ce0.5)2+ doping on Curie temperature is not obvious,but the ferroelectric and piezoelectric properties of KCSNBT-x ceramics are improved significantly with increasing doping content.The ceramics possesses optimum properties at x = 0.3: 2Pr = 16.4 ?C/cm2,d33 = 21 pC/N,Tc = 567 ?.Additionally,the piezoelectric coefficients(d33)of KCSNBT-x ceramics still keep up over 20 pC/N when annealing temperature increased to be 400 ?,demonstrating that KCSNBT-x ceramics possess excellent temperature stability. |
PDF Full Text Request