Journal of Advanced Ceramics
·
2021
·Vol. 10
·期 4
·809-819
·
IF 6.707
Yan Tianxiang,Chen Kaiyuan,Li Chengqi,Liu Min,Wang Jie,Fang Liang,Liu Laijun
(1− x )K 0.5 Na 0.5 NbO 3 − x Bi(Zn 2/3 Nb 1/3 )O 3 ((1− x )KNN− x BZN, x = 0.010, 0.015, 0.020, 0.025, and 0.030) lead-free ceramics were fabricated via a traditional solid-state method. The crystal structure, microstructure, dielectric, and conductivity behavior of this system were studied. Combined with X-ray diffraction (XRD) patterns, Rietveld refinement, and dielectric spectroscopy, an orthorhombic phase was determined for x = 0.010, an orthorhombic-tetragonal mixed phase was identified for x = 0.015, and a rhombohedral symmetry appears in 0.020 ⩽ x ⩽ 0.030. Both 0.98KNN−0.02BZN and 0.975KNN−0.025BZN ceramics exhibit stable permittivity and low dielectric loss tangent (tan δ ) in wide temperature ranges owing to the combination of rhombohedral-tetragonal step-like feature and the diffuse phase transition from tetragonal to cubic. The activation energies of dielectric relaxation and conductivity behavior at high temperatures initially decrease slightly, then drop sharply, and finally decline slowly, which could be attributed to microstructure morphologies and the concentration of oxygen vacancies.
研究领域:
材料科学
·
物理学
✓ 已验证
产品关联
DOI
高影响因子
Materials
·
2021
·Vol. 14
·期 19
·5598
·
IF 3.623
Huajiang Zhou,Shaozhao Wang,Daowen Wu,Qiang Chen,Yu Chen
In this work, a kind of Gd/Cr codoped Bi3TiNbO9Aurivillius phase ceramic with the formula of Bi2.8Gd0.2TiNbO9+ 0.2 wt% Cr2O3(abbreviated as BGTN−0.2Cr) was prepared by a conventional solid-state reaction route. Microstructures and electrical conduction behaviors of the ceramic were investigated. XRD and SEM detection found that the BGTN−0.2Cr ceramic was crystallized in a pure Bi3TiNbO9phase and composed of plate-like grains. A uniform element distribution involving Bi, Gd, Ti, Nb, Cr, and O was identified in the ceramic by EDS. Because of the frequency dependence of the conductivity between 300 and 650 °C, the electrical conduction mechanisms of the BGTN−0.2Cr ceramic were attributed to the jump of the charge carriers. Based on the correlated barrier hopping (CBH) model, the maximum barrier heightWM, dc conduction activation energyEc, and hopping conduction activation energyEpwere calculated with values of 0.63 eV, 1.09 eV, and 0.73 eV, respectively. Impedance spectrum analysis revealed that the contribution of grains to the conductance increased with rise in temperature; at high temperatures, the conductance behavior of grains deviated from the Debye relaxation model more than that of grain boundaries. Calculation of electrical modulus further suggested that the degree of interaction between charge carriersβtended to grow larger with rising temperature. In view of the approximate relaxation activation energy (~1 eV) calculated fromZ″andM″ peaks, the dielectric relaxation process of the BGTN−0.2Cr ceramic was suggested to be dominated by the thermally activated motion of oxygen vacancies as defect charge carriers. Finally, a high piezoelectricity ofd33= 18 pC/N as well as a high resistivity ofρdc= 1.52 × 105Ω cm at 600 °C provided the BGTN−0.2Cr ceramic with promising applications in the piezoelectric sensors with operating temperature above 600 °C.Keywords:Aurivillius phase ceramic;Bi3TiNbO9;electrical conduction behaviors;impedance spectrum;electrical modulus
研究领域:
材料科学
·
电子工程
✓ 已验证
产品关联
DOI
PubMed
高影响因子
CERAMICS INTERNATIONAL
·
2019
·
IF 3.45
Zhidong Xia,Bin Meng,Heng Zhang,Qian Zheng,Wenke Liang,Xinyu Ping
Ce 0.8 Sm 0.2 O 1.9 (SDC)-xMgO (x = 0, 5, 10, 15, and 20 mol%) composite powders were synthesized by a sol-gel method and then densified by spark plasma sintering (SPS) to investigate the effects of MgO additions on the electrical conduction behavior of CeO 2 -based ceramics. The microstructure and electrical performances of the SDC-MgO composite ceramics were characterized and measured by XRD , SEM, TEM, EDS and EIS . Results show that the second phase of MgO segregates at the grain boundaries of SDC when its content is higher than 5 mol% in the ceramics. The SPS process accelerates the formation of MgO lamellar grains with incomplete crystallization. As the MgO content rises from 0 to 20 mol%, the grain boundary and total electrical conductivities first increase and then decrease, and the SDC-5%MgO sample exhibits the highest total conductivity, i.e., 2.76 × 10 −2 S/cm at 650 ° C, which is 9.65% higher than that of pure SDC.
研究领域:
材料科学
·
电化学
✓ 已验证
DOI
高影响因子
IONICS
·
2019
·Vol. 25
·期 7
·3189-3196
·
IF 2.289
Wang Ping,Zhou Yiyang,Xu Pei,Ding Yunsheng
Dielectric relaxation spectroscopy (DRS) was used to investigate the effect of morphological evolution on conductivity behavior of PLA/PCL blends containing P[MPEGMA-IL]. The morphology of blends changes from sea-island morphology into co-continuous morphology with increasing P[MPEGMA-IL] content. P[MEPGMA-IL] could mainly localize in PCL domains and expand to the interface layer between the PLA and PCL phase because of the low viscosity of PCL phase and the high affinity of MEPGMA groups for both polymer phases. The dielectric results were discussed in terms of α relaxation that corresponds to normal and segmental mode movement, interfacial polarization that corresponds to interfacial aggregation of charge carriers, and ac conductivity that originates from conductive network of mobile charge carriers. Co-continuous morphology and high ions concentration lead to the enhancement of segment movement and ion conductive channel in PCL phase, which correspond to high conductivity and low activation energy of PLA/PCL/8P[MEGMA-IL] blend.
研究领域:
材料科学
·
高分子化学
✓ 已验证
产品关联
DOI
高影响因子
危险品化学品经营许可证（带存储）