scholarly journals Phase Formation, Microstructure and Permeability of Fe-Deficient Ni-Cu-Zn Ferrites, (I): Effect of Sintering Temperature

2021 ◽  
Vol 7 (8) ◽  
pp. 118
Author(s):  
Christoph Priese ◽  
Jörg Töpfer
Keyword(s):  
Grain Boundary ◽  
Grain Growth ◽  
Phase Formation ◽  
Maximum Rate ◽  
Single Phase ◽  
Sintering Temperature ◽  
Regular Growth ◽  
Boundary Phase ◽  
Second Phases ◽  
Maximum Permeability

We have studied the densification, phase formation, microstructure, and permeability of stoichiometric and Fe-deficient Ni-Cu-Zn ferrites of composition Ni0.30Cu0.20Zn0.50+zFe2-zO4-(z/2) with 0 £ z £ 0.06 sintered at temperatures from 900 °C to 1150 °C. The shrinkage is shifted from 1000 °C for z = 0 towards lower temperatures and reaches its maximum rate at 900 °C for z = 0.02. Stoichiometric ferrites show regular growth of single-phase ferrite grains if sintered at Ts ≤ 1100 °C. Sintering at 1150 °C leads to the formation of a small amount of Cu2O, triggering exaggerated grain growth. Fe-deficient compositions (z > 0) form Cu-poor stoichiometric ferrites coexisting with a minority CuO phase after sintering at 900–1000 °C. At Ts ≥ 1050 °C, CuO transforms into Cu2O, and exaggerated grain growth is observed. The formation of Cu oxide second phases is investigated using XRD, SEM, and EDX. The permeability of the ferrites increases with sintering temperature up to a maximum permeability of µ = 230 for z = 0 or µ = 580 for z = 0.02, respectively, at Ts = 1000 °C. At higher sintering temperatures, the permeability decreases, which is due to the formation of a microstructure with intra-crystalline porosity in large grains, and a non-magnetic Cu oxide grain boundary phase.

scholarly journals Effect of the Sintering Temperature and Atmosphere on the Grain Growth and Grain Boundary Phase Formation of Pr-Doped ZnO Varistor

1996 ◽  
Vol 104 (1205) ◽  
pp. 44-48 ◽  
Author(s):  
Masato SIDA ◽  
Seong-Yong CHUN ◽  
Naoki WAKIYA ◽  
Kazuo SHINOZAKI ◽  
Nobuyasu MIZUTANI
Keyword(s):  
Grain Boundary ◽  
Grain Growth ◽  
Phase Formation ◽  
Sintering Temperature ◽  
Boundary Phase ◽  
Zno Varistor ◽  
Doped Zno

Effect of CoO Doping on the Sintering Ability and Mechanical Properties of Y-TZP

2004 ◽  
Vol 449-452 ◽  
pp. 265-268 ◽  
Author(s):  
Tetsuhiko Onda ◽  
H. Yamauchi ◽  
Motozo Hayakawa
Keyword(s):  
Mechanical Properties ◽  
Grain Size ◽  
Grain Boundary ◽  
Grain Refinement ◽  
Grain Growth ◽  
Sintering Temperature ◽  
Tetragonal Zirconia ◽  
Boundary Structure ◽  
Grain Boundary Structure ◽  
Boundary Strength

The effect of CoO addition into Y-TZP (Yttria doped Tetragonal Zirconia Polycrystals) was studied on the evolution of its sintering ability, grain size, grain boundary structure and mechanical properties. The doping of a small amount of CoO effectively reduced the sintering temperature. A small amount of CoO up to ~ 0.3 mol% was effective for the suppression of grain growth, but the addition of 1.0 mole % resulted in an enhanced grain growth. The hardness and toughness of the CoO doped TZP were about the same as those of undoped TZP. Furthermore, despite the grain refinement, CoO doped TZP did not exhibit improved mechanical properties. This may be suggesting that CoO dopant had weakened the grain boundary strength.

Simulations of Anisotropic Grain Growth Subject to Thermal Gradients Using Q-State Monte Carlo

2013 ◽  
Vol 135 (4) ◽  
Author(s):  
J. B. Allen ◽  
C. F. Cornwell ◽  
B. D. Devine ◽  
C. R. Welch
Keyword(s):  
Monte Carlo ◽  
Grain Boundary ◽  
Grain Growth ◽  
Single Phase ◽  
Boundary Surface ◽  
Normal Growth ◽  
Thermal Gradients ◽  
Surface Energies ◽  
Generalized Heat Equation ◽  
Mobility Coefficient

The Q-state Monte Carlo, Potts model is used to investigate 2D, anisotropic, grain growth of single-phase materials subject to temperature gradients. Anisotropy is simulated via the use of nonuniform grain boundary surface energies, and thermal gradients are simulated through the use of variable grain boundary mobilities. Hexagonal grain elements are employed, and elliptical Wulff plots are used to assign surface energies to grain lattices. The mobility is set to vary in accordance with solutions to a generalized heat equation and is solved for two separate values of the mobility coefficient. Among other findings, the results reveal that like isotropic grain growth, under the influence of a thermal gradient, anisotropic grain growth also demonstrates locally normal growth kinetics.

The Effect of Heat-Treatment on Thermal Conductivity of Silicon Nitride Ceramics

2011 ◽  
Vol 484 ◽  
pp. 52-56
Author(s):  
Katsumi Yoshida ◽  
Yuki Sekimoto ◽  
Keiichi Katayama ◽  
Thanakorn Wasanapiarnpong ◽  
Masamitsu Imai ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Heat Treatment ◽  
Grain Size ◽  
Grain Boundary ◽  
Grain Growth ◽  
Glassy Phase ◽  
Boundary Phase ◽  
Sintering Additives ◽  
Heat Treated ◽  
Si3n4 Ceramics

Alpha- or beta-Si3N4 powder with larger grain size was uses as starting material, and the effect of heat-treatment on thermal conductivity of Si3N4 ceramics using MgO, Y2O3 and SiO2 as sintering additives was investigated in terms of their microstructure and the amount of grain boundary phase. Most of the components derived from sintering additives existed as glassy phase in sintered Si3N4. After heat-treatment at 1950oC for 8 h, the amount of glassy phase significantly decreased, and then small amount of glassy phase existed in Si3N4 ceramics was crystallized as Y2O3 and Y2Si3N4O3. In the case of Si3N4 ceramics using SN-7 powder, thermal conductivity of heat-treated Si3N4 was around twice of the value of sintered Si3N4, and the thermal conductivity was increased from 41.4 to 87.2 W/m•K due to not only the reduction of grain boundary phase but also the grain growth. In the case of Si3N4 using SN-F1 powder, thermal conductivity of Si3N4 ceramics was also significantly increased from 36.0 to 73.2 W/m•K after heat-treatment. In this case, the reduction of grain boundary phase mainly affected the thermal conductivity of Si3N4 ceramics because the grain size of heat-treated Si3N4 was nearly the same as that of sintered Si3N4. The reduction of grain boundary phase from Si3N4 was effective for the improvement of their thermal conductivity in addition to grain growth of Si3N4.

Grain Boundary Phase Formation and Magnetic Properties of NdFeB/Nd Multilayered Films

2009 ◽  
Vol 48 (3) ◽  
pp. 033002 ◽  
Author(s):  
Deshan Li ◽  
Shunji Suzuki ◽  
Takashi Horikawa ◽  
Masahiro Itoh ◽  
Ken-ichi Machida
Keyword(s):  
Magnetic Properties ◽  
Grain Boundary ◽  
Phase Formation ◽  
Boundary Phase ◽  
Multilayered Films

Sintering of Silicon Carbide Ceramics with Co-Addition of Gadrinium Oxide and Silica and their Mechanical Properties

2011 ◽  
Vol 484 ◽  
pp. 117-123
Author(s):  
Toyohiko Yano ◽  
Yasutaka Horie ◽  
Masamitsu Imai ◽  
Katsumi Yoshida
Keyword(s):  
Mechanical Properties ◽  
Grain Boundary ◽  
Bending Strength ◽  
Sintering Temperature ◽  
Applied Pressure ◽  
Boundary Phase ◽  
Homogeneous Distribution ◽  
Carbide Ceramics ◽  
Co Addition ◽  
Silicon Carbide Ceramics

Effects of simultaneous addition of SiO2 and gadrinium oxide on densification of SiC ceramics were examined, and relation between microstructure and their mechanical properties were discussed. Total 11wt% of Gd2O3 and SiO2 were mixed with fine -SiC powder. The weight of Gd2O3 in (Gd2O3 + SiO2) were set as 0, 20, 40, 60, 80 and 100%. The mixture was hot-pressed at 1950oC under 40 MPa applied pressure for 1 h. In the case of 40Gd2O3 and 80Gd2O3 compositions, the effect of sintering temperature from 1900 to 2000oC was also examined. The bulk density increased with increasing Gd2O3 content at the sintering temperature of 1950oC. Bending strength of the sintered bodies also improved with increasing Gd2O3 content generally, but at 40Gd2O3 composition, the maximum over ~800 MPa was observed. Young’s modulous, Vickers hardness and fracture toughness also increased with increasing Gd2O3 content. The distribution of grain boundary phase was not homogeneous. Evaporation of additives, mainly SiO2, caused non-homogeneous distribution of grain boundary phase between outside and inside of sintered bodies. High temperature bending strength of 80Gd2O3 specimen was superior than that of 40Gd2O3 specimen.

scholarly journals INFLUENCE OF SINTERING TEMPERATURE ON PHASE FORMATION AND OPTICAL PROPERTIES OF LEAD-FREE FERROELECTRIC BI0.5NA0.5TIO3 MATERIALS

2018 ◽  
Vol 54 (1A) ◽  
pp. 104
Author(s):  
Le Thi Hai Thanh
Keyword(s):  
Optical Properties ◽  
Phase Formation ◽  
Single Phase ◽  
Sintering Temperature ◽  
Electronic Devices ◽  
Sol Gel ◽  
Ferroelectric Materials ◽  
Lead Free ◽  
Sintering Time ◽  
Piezoelectric Characteristics

Pb(Zr,Ti)O3 based ferroelectric materials have been widely used in electronic devices even though they were banned due to the toxicity of lead on health and environment. Among the lead-free ferromagnetic materials, Bi0.5Na0.5TiO3 has received much attention because their ferroelectric and piezoelectric characteristics are comparable to Pb(Zr,Ti)O3. In this report, Bi0.5Na0.5TiO3 was fabricated by sol-gel method. The influence of fabricating conditions such as gelization, sintering temperature on crystallinity was studied. The result showed that Bi0.5Na0.5TiO3 was in single phase when compenstation amount of Na in gelization is 40 mol%; sintering temperature higher than 800 oC and sintering time is 2 h. The bandgap of Bi0.5Na0.5TiO3 which estimated from absorption spectroscopy is in the range of 3.01 - 3.18 eV.

Analytical TEM study of a yttria stabilized zirconia/glass composite

1988 ◽  
Vol 46 ◽  
pp. 572-573
Author(s):  
Yung-Jen Lin ◽  
Peter Angelini ◽  
Martha L. Mecartney
Keyword(s):  
Grain Size ◽  
Grain Boundary ◽  
Grain Growth ◽  
Room Temperature ◽  
Tetragonal Zirconia ◽  
Yttria Stabilized Zirconia ◽  
Boundary Phase ◽  
Stabilized Zirconia ◽  
High Toughness ◽  
M Phase

Yttria stabilized zirconia is a versatile ceramic material. It can be used for structural components or as a solid electrolyte. Its properties (such as high toughness) are strongly affected by the microstructure. In partially stabilized zirconia, the high toughness is mainly due to the toughening effect of a tetragonal (t) to monoclinic (m) phase transformation in the vicinity of a crack. Retention of tetragonal zirconia at room temperature is important for fabricating transformation toughened materials. To completely retain tetragonal zirconia at room temperature the grain size of the material must be less than a critical size. In yttria stabilized zirconia this critical grain size depends on the yttria concentration. Grain growth of yttria stabilized zirconia is also influenced by the amount of yttria in the grains. These previous studies, however, have focused on the behavior of materials with minimal glassy grain boundary phases. In contrast, in commercial polycrystalline zirconia often a significant amount of glassy grain boundary phase is present. This current research seeks to elucidate the effects of these grain boundary phases on the grain growth in yttria stabilized zirconia ceramics.

The Control of Zn for ZST Microwave Ceramics With Low Sintering Temperature

1999 ◽  
Vol 606 ◽  
Author(s):  
Yong H. Park ◽  
Moo Y. Shin ◽  
Ji M. Ryu ◽  
Kyung H. Ko
Keyword(s):  
Dielectric Properties ◽  
Side Effects ◽  
Grain Boundary ◽  
Sintering Temperature ◽  
Annealed Sample ◽  
Microwave Properties ◽  
Microwave Ceramics ◽  
Mixed Powder ◽  
Second Phases ◽  
Low Sintering Temperature

AbstractZnO addition for low-T sintering of ZST has serious side effects such as decrease of Q × f value. In this work, the curing of these side effects without any further chemical additivesand causing degradation of other dielectric properties have been presented. After sintered at 1350°C for 2h. samples were annealed in oxygen at 900 ∼ 1100°C for 5hr. It was observed that Q × f value of post-annealed sample at 900°C could recovered up to 46000 from the as-sintered value of 40000. Because there were no formations of second phases or significant changes inlattice constants, which could affect microwave properties of ZST. However, it was found that only for the specimens annealed at 900°C, Zn was almost depleted from grin inside and diffused toward grain boundary. So, it is suggested that the out-diffusion of Zn is responsible for the recovery of Q × f value. Moreover, when the amount of Zn incorporation increased via successive calcination and sintering of pre-mixed powder of ZST and ZnO, Q × f value of 33000 also could enhanced up to 39000 due to the redistribution of Zn near grain boundary by out-diffusion.

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