Papers by Keyword: Low Temperature Sintering

Abstract: MgTa₂O₆ powders with the tetragonal phase have been synthesized by mixed oxide method at 1100 °C when the molar ratios of MgO and Ta₂O₅ increase from 1:1 to 1.2:1. The microwave dielectric properties of sintered MgTa₂O₆ ceramics without additives at 1400°C for 6h, which consists of tetragonal and orthorhombic phases have been investigated. The results show that the ceramic possesses a dielectric constant of 27.5, a high Q×f value of 156000 GHz and a temperature coefficient of resonant frequency of 21.6 ppm/°C at 6-10 GHz. Different amounts of CuO has been used as sintering additives to lower the sintering temperature of MgTa₂O₆ ceramics. The effect of the CuO doping agent on the microstructure, densification and the microwave dielectric properties of MgTa₂O₆ ceramics has been studied using X-ray diffraction, scanning electron microscope and HP8720ES network analyzer. The results indicate that the 1-5 wt. % CuO dopant can lower the sintering temperatures of this materials dramatically. The second phase of CuTa₂O₆ was found in MgTa₂O₆ ceramics, which caused the deterioration of Q×f value of the ceramics.

Abstract: Nano-sized electrolyte of CeO₂ doped 8YSZ with 2%mol CuO (YSZDC)powders were synthesized by solid state reaction method. Powder characteristics and electrical properties was characterized by XRD,SEM and Electrochemical workstation.The results demonstrate that the as-synthesized Y_0.08Zr_0.72Ce_0.2O_1.6 (YSZDC) and Y_0.08Zr_0.72Ce_0.18Cu _0.02O_1.6-δ(YSZDC-Cu_0.02) possessed similar powder characteristics, including cubic fluorite crystalline structure.About 150 °C reduction in densification temperature of Y_0.08Zr_0.72Ce_0.18Cu_0.02O_1.6-δ was obtained when compared with Y_0.08Zr_0.72Ce_0.2O_1.6.The YSZDC-Cu_0.02 pellets sintered at 1300 °C and the YSZDC sintered at 1450 °C exhibited relative densities of 95.66% and 94.73%,respectively.Electrolyte matrixs were prepared for electrolyte-supported SOFCs(ES-SOFC) , the suspension of NiO-YSZ anode was sprayed on the electrolyte, after co-sintering at 1300°C,electrolyte matrixs and anode were well adhered each othert, without connecting pores and cracks observed. Moerover, well electricity performance were showed by YSZDC and YSZDC-Cu_0.02 at a testing temperature of 750°C,And the electrolyte conductivity didn’t decrease obviously with dopping CuO.

Abstract: (Bi1.5Zn0.5)(Zn0.5Nb1.5)O7 (BZN) ceramic samples were prepared by solid state reaction, In order to reduce the sintering temperature of BZN ceramic we have used liquid coating technology to dope CuO by precursor solution of CuSO4. The sintering behavior, microstructures, phase structures, and dielectric properties were studied. The process reduces the amount of sintering aid and minimized the negative impact of sintering aid on dielectric properties. A ceramic composite which could be sintered well at 900°C and showed good dielectric properties of εr=161,tanδ=0.005 and TCF=-398ppm/°C（1MHz）was obtained when 0.5mol/l CuSO4 was added to the (Bi1.5Zn0.5)(Zn0.5Nb1.5)O7 ceramic.

Abstract: The effect of CaO-B₂O₃-SiO₂ glass on the densification, microstructure and microwave dielectric properties of Ba₄Nd_9.33Ti₁₈O₅₄ ceramics was investigated in this work. It was found that the addition of a few amount of glass (≤2%) could effectively decrease the sintering temperature owing to the viscous sintering. However, locally porous structures were formed when overmuch glass was added because of enwrapped air bubbles and rapid grain growth. In addition, the amount of remaining glass after sintering could be decreased due to the re-crystallization of CaO-B₂O₃-SiO₂ glass. Sol-gel derived Ba₄Nd_9.33Ti₁₈O₅₄ ceramics containing 2 wt% glass can be well densified at 950°C and exhibit good microwave dielectric properties of ε_r=68 and Q×f=7400 GHz.

Abstract: Ti/Al(Ti-50at.%Al) composite powders were prepared by high-energy ball milling followed by reaction sintering heat treatment at 550°C ~ 650°C for 2 hours. Mechanical alloying of TiAl had been performed in a high energy plant ball after different milling times and pre-sintered at different temperatures. The particle sizes of Ti/Al powders were analyzed by scanning electron microscopy (SEM). X-ray diffraction (XRD) analysis was performed for microstructural characterization. The results show that microstructural and morphological changes of high energy milled powder are studied as a function of milling time. Over 600°C TiAl powders are completely alloyed by being sintered at different temperatures. The powders are mainly composed of γ-TiAl as well as a small amount of AlTi3. The TiAl alloy powders of high energy ball mill/2h and sintered at 650°C/2h get plasma spheroidization. Spheroidizing powders with fine texture, γ-TiAl and AlTi₃ phase, particle size of 10~40μm are obtained.

Abstract: BaZr_0.25Ti_0.75O₃ (BZT) ceramics were prepared by conventional ceramic process at a relatively low sintering temperature and with an addition of Li₂O as the liquid-phase sintering aid. X-ray diffraction characterized results showed that the main crystal phase of the samples with 1.0wt% Li₂O additive sintered at 1050°C～1250°C for 4h presented perovskite structure. The dielectric properties of BZT ceramics have been investigated. The dielectric constant of 1.0wt% Li₂O doped BZT sintered at 1150°C decreased, and the dielectric loss increased by 0.0012 compared with that of the pure BZT sintered at 1450°C.

Abstract: Lead-free K_0.5Na_0.5NbO₃-xwt% (0.4ZnO-0.6B₂O₃) ceramics were synthesized by conventional ceramics process. The co-doping of ZnO and B₂O₃ can decrease the sintering temperature of K_0.5Na_0.5NbO₃ ceramics to 1000°C, and the samples show high relative density around 96%. X-ray diffraction (XRD) reveals that Co-doping of ZnO and B₂O₃ induces lattice distortion. Liquid phase is observed by scanning electron microscopy (SEM), which is resulted from the addition of ZnO and B₂O₃. The ceramics show better piezoelectric and dielectric properties with planar electromechanical coupling factor k_p= 40.7%, piezoelectric constant d₃₃=117pC/N, dielectric constant ε^T₃₃/ε₀=318.6, and loss tangent tanδ=0.034.

Abstract: The development of consumer electronics has meant that the component market is subjected of major economic issues. The economic battle goes through a search of lower manufacturing costs of electronic components together with an improvement in their performance, especially multilayer ceramic capacitors. The dielectric properties of the compound MgTiO3 (r  17, ε =100 ppm/°C, Tan (δ) <10-3) make this material a very good candidate for the manufacture of multilayer capacitors. In contrast, the high sintering temperature of this ceramic (1350 ° C), precludes the realization of multilayer capacitors with copper inner electrodes (T melting = 1083 ° C) less expensive than noble metals (Pd or Pt). Recent studies have shown that it is possible to reduce the sintering temperature by adding sintering agents. Additions made on MgTiO3 are glass phases (BBS 5Z2B, SBAZN, BBZS). Interesting dielectric properties were obtained in the case of system MgTiO3 + BBZS sintered at 1030 ° C: a dielectric permittivity epsilon r = 15.46, a temperature coefficient of 207 ppm / ° C, dielectric losses Tan (δ) <10-3.

Abstract: Ba₄Sm_9.33Ti₁₈O₅₄ (BST) ceramics were prepared by conventional solid-state reaction method. The effect of CuO-Bi₂O₃ co-doping on the sintering behavior and microwave dielectric properties of BST ceramics has been investigated. The results indicated that when the total addition of CuO-Bi₂O₃ doping agent was 1.0wt%, the sintering temperature of BST ceramics was reduced to 1240°C as a result of liquid-phase sintering effect derived from CuBi₂O₄. When the total addition of CuO-Bi₂O₃ was fixed at 1.0wt%, the microwave dielelctric properties of BST were improved by adjusting the mass percentage of Bi₂O₃. With the increase of Bi₂O₃ amount from 20wt% to 80wt%, the dielectric constant (ε_r) decreased, the quality factor (Q•f) increased and the temperature coefficient of resonant frequency (τ_f) shifted from negative value to positive value. The excellent microwave dielectric properties of ε_r=82.51, Q•f=7878GHz and τ_f=+6.02ppm/ were obtained for the sample with Bi₂O₃ amount of 80wt% when sintered at 1240°C for 3h.

Abstract: The utilization of steel slag as resource is very important in the circle economy of metallurgy industry. Because the composition of steel slag is similar to that of the raw materials of ceramic industry, the sintering process of ceramics with steel slag as one of the raw materials was studied, and the ceramic products of high performance were abstained. Based on the study above, the microstructure of slag ceramic and its effect on the performance of ceramic were studied combining the analysis methods of SEM, DTA and XRD and the software FactSage. It’s found that the diopside phase was formed in the sintering process, which has significant effects on low temperature sintering and ceramic strength improving. Simulation by software FactSage showed that the diopside phase appears when the content of the steel-slag reaches 25%, while the content of slag is higher there are more diopside phase generation.