• Title/Summary/Keyword: Solid state sintering

Search Result 218, Processing Time 0.042 seconds

Effect of Na2CO3 Addition on Grain Growth Behavior and Solid-state Single Crystal Growth in the Na0.5Bi0.5TiO3-BaTiO3 System (Na0.5Bi0.5TiO3-BaTiO3 계에서 입자성장 및 고상단결정성장에 미치는 Na2CO3 첨가 효과)

  • Moon, Kyoung-Seok
    • Journal of Powder Materials
    • /
    • v.25 no.2
    • /
    • pp.104-108
    • /
    • 2018
  • Grain-growth behavior in the $95Na_{1/2}Bi_{1/2}TiO_3-5BaTiO_3$ (mole fraction, NBT-5BT) system has been investigated with the addition of $Na_2CO_3$. When $Na_2CO_3$ is added to NBT-5BT, the growth rate is higher than desired and grains are already impinging each other during the initial stage of sintering. The grain size decreases as the sintering temperature increases. With the addition of $Na_2CO_3$, a liquid phase infiltrates the interfaces between grains during sintering. The interface structure can be changed to be more faceted and the interface migration rate can increase due to fast material transport through the liquid phase. As the sintering temperature increases, the impingement of abnormal grains increases because the number of abnormal grains increases. Therefore, the average grain size of abnormal grains can be decreased as the temperature increases. The phenomenon can provide evidence that grain coarsening in NBT-5BT with addition of $Na_2CO_3$ is governed by the growth of facet planes, which would occur via mixed control.

Synthesis and Characterization of BaTiO3 Powder by Solid State Method (고상반응법을 이용한 BaTiO3 합성 및 특성 평가)

  • Kim, Yong Jin;Choi, Moon Hee;Shin, Hyo Soon;Ju, Byeong-Kwon;Chun, Myoung Pyo
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
    • /
    • v.33 no.6
    • /
    • pp.483-489
    • /
    • 2020
  • BaTiO3 powder was synthesized by a solid-state reaction using BaCO3 and TiO2. Different calcination temperatures (800℃, 850℃, 900℃, and 950℃) were set to investigate their effects on the properties of BaTiO3 powder. The synthesized BaTiO3 phase was confirmed to be a single phase by XRD, and the tetragonality (c/a) and crystallite size were calculated. Thereafter, each calcinated BaTiO3 was sintered at five different sintering temperatures (1,100℃, 1,150℃, 1,200℃, 1,250℃, and 1,300℃), and the tetragonality, density, porosity, dielectric constant, and grain size were measured. As the calcination temperature increased, the tetragonality and crystallite size also increased, to 1.008 and 66 nm, respectively, at 950℃. Moreover, most pellets showed increased density, dielectric constant, and tetragonality as the sintering temperature increased up to 1,250℃; the same parameters slightly decreased at 1,300℃. It is noteworthy that the tetragonality of BaTiO3 at 1,250℃ exhibits a very high c/a value of 1.0084. In addition, the grain size and dielectric constant measured near the Curie temperature increased as the sintering temperature increased.

Direct Microwave Sintering of Poorly Coupled Ceramics in Electrochemical Devices

  • Amiri, Taghi;Etsell, Thomas H.;Sarkar, Partha
    • Journal of Electrochemical Science and Technology
    • /
    • v.13 no.3
    • /
    • pp.390-397
    • /
    • 2022
  • The use of microwaves as the energy source for synthesis and sintering of ceramics offers substantial advantages compared to conventional gas-fired and electric resistance furnaces. Benefits include much shorter processing times and reaching the sintering temperature more quickly, resulting in superior final product quality. Most oxide ceramics poorly interact with microwave irradiation at low temperatures; thus, a more complex setup including a susceptor is needed, which makes the whole process very complicated. This investigation pursued a new approach, which enabled us to use microwave irradiation directly in poorly coupled oxides. In many solid-state electrochemical devices, the support is either metal or can be reduced to metal. Metal powders in the support can act as an internal susceptor and heat the entire cell. Then sufficient interaction of microwave irradiation and ceramic material can occur as the sample temperature increases. This microwave heating and exothermic reaction of oxidation of the support can sinter the ceramic very efficiently without any external susceptor. In this study, yttria stabilized zirconia (YSZ) and a Ni-YSZ cermet support were used as an example. The cermet was used as the support, and a YSZ electrolyte was coated and sintered directly using microwave irradiation without the use of any susceptor. The results were compared to a similar cell prepared using a conventional electric furnace. The leakage test and full cell power measurement results revealed a fully leak-free electrolyte. Scanning electron microscopy and density measurements show that microwave sintered samples have lower open porosity in the electrode support than conventional heat treatment. This technique offers an efficient way to directly use microwave irradiation to sinter thin film ceramics without a susceptor.

Low-temperature Sintering Behavior of TiO2 Activated with CuO

  • Paek, Yeong-Kyeun;Shin, Chang-Keun;Oh, Kyung-Sik;Chung, Tai-Joo;Cho, Hyoung Jin
    • Journal of the Korean Ceramic Society
    • /
    • v.53 no.6
    • /
    • pp.682-688
    • /
    • 2016
  • In $TiO_2$-CuO systems, low-temperature sinterability was investigated by a conventional sintering method. Sintering temperatures were set at under $950^{\circ}C$, at which the volume diffusion is inactive. The temperatures are less than the melting point of Ag ($961^{\circ}C$), which is often used as an internal conductor in low-temperature co-fired ceramic technology. To optimize the amount of CuO dopant, various dopant contents were added. The optimum level for enhanced densification was 2 wt% CuO. Excess dopants were segregated to the grain boundaries. The segregated dopants supplied a high diffusion path, by which grain boundary diffusion improved. At lower temperatures in the solid state region, grain boundary diffusion was the principal mass transport mechanism for densification. The enhanced grain boundary diffusion, therefore, improved densification. In this regard, the results of this study prove that the sintering mechanism was the same as that of activated sintering.

Impedance Properties of Phase-Pure Titanium Dioxide Ceramics Sintered at Different Temperatures

  • Cui, Liqi;Niu, Ruifeng;Wang, Weitian
    • Korean Journal of Materials Research
    • /
    • v.32 no.4
    • /
    • pp.181-185
    • /
    • 2022
  • In this study, phase-pure titanium dioxide TiO2 ceramics are sintered using standard high-temperature solid-state reaction technique at different temperatures (1,000, 1,100, 1,200, 1,300, 1,400 ℃). The effect of sintering temperature on the densification and impedance properties of TiO2 ceramics is investigated. The bulk density and average grain size increase with the increase of sintering temperature. Impedance spectroscopy analysis (complex impedance Z* and complex modulus M*), performed in a broad frequency range from 100 Hz to 10 MHz, indicates that the TiO2 ceramics are dielectrically heterogeneous, consisting of grains and grain boundaries. The complex impedance Z* -plane indicates the resistance of grains of the TiO2 ceramics increases with increasing sintering temperature, while that of grain boundaries develops in the opposing direction. The complex modulus M*-plane shows a grain capacitance that seems to be independent of the sintering temperature, while that of the grain boundaries decreases with increasing sintering temperature. These results suggest that different sintering temperatures have effects on the microstructure, leading to changes in the impedance properties of TiO2 ceramics.

Synthesis of Solid Electrolyte Nasicon by Solid State Reaction

  • Kim, Cheol-Jin;Chung, Jun-Ki;Lim, Sung-Ki;Rhee, Meung-Ho
    • The Korean Journal of Ceramics
    • /
    • v.2 no.1
    • /
    • pp.25-32
    • /
    • 1996
  • Solid electroyte nasion was synthesized by the optimized solid state reaction minimizing the volume fraction of secondary $ZrO_2$ and glassy phases. To compensate for the evaporation of Na and P during heat-treatment, excess Na and P were added to the starting composition $Na_{1+x} Zr_2 Si_x P_{d-x} O_{12}$ (x=2.1). Phases pure nasicon comparable in volume fraction to the one obtaied from sol-gel process were synthesized after the reaction at $1100~1150^{\circ}C$,$ P_{O2}>=0.1-0.15 $$ZrO_2$ increased with the heat-treatment time due to the decomposition of nasicon phase and that of glassy phase increased as partial oxygen pressure decreased. The synthesized nasion showed a good electrical conductivity of $-1{\times}10^{-2}({\omega}{\cdot}cm)^{-1}$ at $350^{\circ}C$.

  • PDF

Leucite Synthesis from Solid-State Sintering (고상법에 의한 Leucite 합성)

  • Yoon, Dong-Sup;Lee, Byung-Ha
    • Journal of the Korean Ceramic Society
    • /
    • v.42 no.4
    • /
    • pp.282-286
    • /
    • 2005
  • Leucite crystal has been utilized for dental porcelain due to its high thermal expansion coefficient to meet its counter metal side. Many industrial applications of leucite from the incongruently melting of potassium feldspar are used and its minimum temperature of crystallization is $1150^{\circ}C$. This study aimed to get leucite crystal from lower temperature through congruently melting, and the starting materials are taken from K-feldspar mainly, and aluminum hydroxide and potassium carbonate are additionally supplied to meet stoichiometry of leucite. We report that the leucite crystal can be synthesized in congruently melting from the temperature $950^{\circ}C$ through solid-state sintering with k-feldspar, potassium carbonate and aluminum hydroxide.