Chunhua Gao

Study on Ferroelectric and Dielectric Properties of La-Doped CaBi4Ti4O15-Based Ceramics

Abstract Lanthanum doped bismuth layer structured ferroelectrics (BLSFs) Ca1-xLaxBi4(Ti0.9W0.1)4O15(x = 0, 0.2. 0.3, 0.4, 0.6) ceramics were prepared by solid-state reaction method. X-ray diffraction (XRD) patterns showed that single phase was formed when x = 0 ∼ 0.6. The effects of La3+ doping on dielectric, piezoelectric and ferroelectric properties of Ca1-xLaxBi4(Ti0.9W0.1)4O15 ceramics were studied. Ca0.7La0.3Bi4(Ti0.9W0.1)4O15 ceramic had optimal properties, its dielectric constant was 166.85, dielectric loss was 0.0063, piezoelectric strain constant was 11 pc·N−1. remanent polarization was 18.1 μC·cm−2 and coercive field was 118 kV·cm−1. SEM micrographs showed that the grains of CaBi4Ti4O15-based ceramics were plate-like. The results of energy spectrum analysis (EDS) showed that La3- incorporation could increase Bi/Ca ratio.

Influence of CeO2 doping amount on property of BCTZ lead-free piezoelectric ceramics sintered at low temperature

Abstract Ba 0.85 Ca 0.15 Ti 0.9 Zr 0.1 O 3 (BCTZ) lead-free piezoelectric ceramics co-doped with CeO 2 ( x =0.1 wt.%, 0.2 wt.%, 0.3 wt.%, 0.4 wt.%, 0.5 wt.%) and Li 2 CO 3 (0.6 wt.%) were prepared by conventional solid-state reaction method. Influence of CeO 2 doping amount on the piezoelectric properties, dielectric properties, phase composition and microstructure of prepared BCTZ lead-free piezoelectric ceramics doped with Li 2 CO 3 were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM) and other analytical methods. The results showed that the sintered temperature of BCTZ lead-free piezoelectric ceramics doped with CeO 2 decreased greatly when Li 2 CO 3 doping amount was 0.6 wt.%; a pure perovskite structure of BCTZ lead-free piezoelectric ceramics co-doped with Li 2 CO 3 and CeO 2 and sintered at 1050 °C could also be obtained. The piezoelectric constant ( d 33 ), the relative permittivity ( ɛ r ) and the planar electromechanical coupling factor ( k p ) of BCTZ ceramics doped with Li 2 CO 3 increased firstly and then decreased, the dielectric loss (tan δ ) decreased firstly and then increased and decreased at last when CeO 2 doping amount increased. The influence of CeO 2 doping on the properties of BCTZ lead-free piezoelectric ceramics doped with Li 2 CO 3 were caused by “soft effect” and “hard effect” piezoelectric additive and causing lattice distortion. When CeO 2 doping amount ( x ) was 0.2 wt.%, the BCTZ ceramics doped with Li 2 CO 3 (0.6 wt.%) and sintered at 1050 °C possessed the best piezoelectric property and dielectric property with d 33 of 436 pC/N, k p of 48.3%, ɛ r of 3650, tan δ of 1.5%.

Study on dielectric property of BST based ceramics doped with MgTiO3

ABSTRACT (Ba0.65Sr0.35)TiO3 (BST) ceramics doped with MgTiO3 were prepared by solid state method. Influence of MgTiO3 doped amount on dielectric property and microstructure of BST ceramics were investigated. The results showed that MgTiO3 doping could fine crystal grain size and made crystal grain size uniform and pore decrease and density increase. MgTiO3 doping could decrease dielectric loss (tanδ) and increase dielectric constant(ϵr) of BST ceramics and increase the alternating current (AC) withstand voltage strength (Eb) and improve the capacitance temperature property. When MgTiO3 doping amount was 0.8wt.%, the BST ceramics had good comprehensive property, ϵr of 4350, tanδ of 0.0055, Eb of 5.7×103 V/mm (AC), the capacitance temperature property was suited for Y5U.

Structure and dielectric property of CaTiSiO5 doped BST ceramics sintered at low temperature

ABSTRACT Structure and dielectric property of CaTiSiO5 doped (Ba, Sr)TiO3(barium strontium titanate, BST) capacitor ceramics were studied by means of X-ray diffraction(XRD),Scanning electron microscopy(SEM) and traditional solid sate sintered method. The results showed that dielectric loss of BST ceramics doped with CaTiSiO5 had low value, moving effect and broadening effect of CaTiSiO5 for curie peak of BST ceramics were obvious. Dielectric constant(ϵr) increased firstly and then decreased, dielectric loss (tanδ) increased firstly and then decreased, AC withstand voltage strength(Eb) increased firstly and then decreased, capacitance temperature changing rate(ΔC/C) decreased firstly and then increased in the negative temperature range and positive temperature range, when CaTiSiO5 doping amount increased. The BST ceramics possessed good comprehensive property with ϵr of 2540, tanδ of 0.0036, Eb of 5.6 kV/mm(AC), ΔC/C of −18.9∼20.6% in the temperature range of −30°∼85°, the capacitance temperature characteristic was suited for Y5S, when CaTiSiO5 doping amount was 0.8wt.%.

Effect of zirconium content on the property of BCTZ lead-free piezoelectric ceramics

Ba_0.85Ca_0.15Ti_1-yZr_yO₃ (BCTZ) (y =0.05, 0.10, 0.15, 0.2) lead-free piezoelectric ceramics were prepared by conventional solid state method. Effects of Zr content on the piezoelectric and dielectric properties and microstructure of BCTZ lead-free piezoelectric ceramics were investigated. The results show that the average crystal grain size of BCTZ increases gradually, the crystal grain uniformity goes down; all the samples exhibit a pure perovskite structure and no trace of impurity phase was observed. The piezoelectric constant(d₃₃), the planar electromechanical coupling factor (k_p) of BCTZ ceramics increases first and then decreases, the relative permittivity (ε_r) increases gradually, the dielectric loss (tanδ) increases first and then decreases when Zr content increases. When Zr content (y) is 0.10, the BCTZ ceramics sintered at 1450, possess the best piezoelectric properties and dielectric properties whose d₃₃ is 424pC/N, k_p is 48.83%,ε_r is 4364, tanδ is 1.12%.

Influence of barium content on the properties and structure of low temperature sintered BCZT lead-free piezoelectric ceramics

The influence of barium content on dielectric and piezoelectric properties of low temperature sintered (Ba_xCa_1-x)(Zr_0.1Ti_0.9)O₃ doped with 0.2wt.%Li₂CO₃ (BCZT-0.2Li) lead-free piezoelectric ceramics was studied by scanning electron microscope(SEM) and X-ray diffraction(XRD) and other analytical methods and conventional solid state method. TiO₂ was chemically pure raw materials, other raw materials were analytical pure raw materials. The results showed that with the increasing of the content of barium, the grain size of BCZT-0.2Li ceramics decreased gradually, the diffraction peaks of perovskite structure was obvious, there was miscellaneous peak.With the increasing of the content of barium, the planar electromechanical coupling coefficient(k_p)and the piezoelectric strain constant(d₃₃)and the thickness electromechanical coupling coefficient(k_t)and the dielectric constant(ε_r) of low temperature sintered BCZT-0.2Li ceramics all increased first and then decreased, dielectric loss(tanδ)of low temperature sintered BCZT ceramics decreased first and then increased. When the content of barium was 0.85 mol, the properties of low temperature sintered BCZT-0.2Li ceramics was optimum, which k_p was 0.42, d₃₃ was 87 pC/N, kt was 0.046, tanδ was 0.013, ε_r was 2020, the sintered temperature was 1050°C.

Influence of Co 2 O 3 doped amount on the properties of (Ba 0.85 Ca 0.15 )(Zr 0.1 Ti 0.9 )O 3 lead-free piezoelectric ceramics

The influence of Co₂O₃ doped amount on dielectric and piezoelectric properties of (Ba_0.85Ca_0.15)(Zr_0.1Ti_0.9)O₃ (BCZT) lead-free piezoelectric ceramics was studied by scanning electron microscope(SEM) and X-ray diffraction(XRD) and other analytical methods and conventional solid state method. TiO₂ was chemically pure raw materials, other raw materials were analytical pure raw materials. The results showed that Perovskite structure of BCZT lead-free piezoelectric ceramics did not change when doped with Co₂O₃, the intensity of diffraction peaks of BCZT increased first and then decreased, the grain crystal size of ceramics increased first and then decreased, the density of ceramics increased first and then decreased when Co₂O₃ doped amount increased. The microstructure of ceramics was the best when Co₂O₃ doped amount was 0.40 wt.%. This was also reason for the good piezoelectric properties. The piezoelectric properties(d₃₃, k_p, k_t) of BCZT lead-free piezoelectric ceramics increased first and then decreased, the relative dielectric constant(er) decreased, dielectric loss increased first and then decreased when Co₂O₃ doped amount increased. The comprehensive performance of BCZT lead-free piezoelectric ceramics was optimum when Co₂O₃ doped amount was 0.40 wt.% which piezoelectric strain constant(d₃₃) was 171pC/N, relative dielectric constant(ε_r) was 22400, planar electromechanical coupling coefficient(k_p) was 0.478, dielectric loss was 0.018, electromechanical coupling coefficient of thickness(k_t) was 0.041, sintered temperature was 1340°C.