研究者詳細 - 徳永　智春

論文 - 徳永　智春

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Healing behavior of microcracks on the surface of yttria-stabilized polycrystals using an ultrafast high-temperature sintering method 査読有り

Sato, T; Kodaira, A; Tokunaga, T; Morita, K; Yamamoto, T

CERAMICS INTERNATIONAL 51 巻 ( 4 ) 頁： 4178 - 4184 2025年2月

記述言語：英語出版者・発行元：Ceramics International

A technique to heal microcracks on ceramic surfaces in a relatively short time is an attractive proposition for extending the lifetime of ceramics. To this end, we used the ultrafast high-temperature sintering (UHS) method, which permits a rapid temperature increase, to heal Vickers indentation microcracks generated in a 4 mol% Y2O3-doped ZrO2 polycrystal. We examined the microstructure following microcrack healing using transmission electron microscopy and scanning electron microscopy with continuous focused ion beam slicing along the microcrack plane. This revealed that the microcrack healing process involves crack pinching and neck formation, followed by the growth of the neck. The microcracks were fully healed at the surface by UHS treatment at 2000 °C for 20 s. However, residual pores corresponding to the unhealed state were observed inside the material. We hypothesized that these pore residues were caused by significant grain coarsening during UHS. It is essential to optimize the UHS temperature and time to account for grain coarsening and facilitate the application of this method to microcrack healing.

DOI： 10.1016/j.ceramint.2024.11.394

Microstructural analysis of flash-healed Vickers-indented microcracks near positive/negative electrodes on the (001) surface of cubic zirconia single crystals under direct current electric fields 査読有り

Kayukawa, S; Katsuyama, Y; Kodaira, A; Tokunaga, T; Morita, K; Yamamoto, T

CERAMICS INTERNATIONAL 50 巻 ( 19 ) 頁： 37348 - 37355 2024年10月

記述言語：英語出版者・発行元：Ceramics International

Flash healing is a technique that uses power spikes to rapidly repair microcracks on ceramic surfaces. In this study, the microstructures of flash-healed Vickers-indented microcracks near the positive/negative electrodes under a DC electric field were examined by scanning transmission electron microscopy. The microstructural morphology near the positive electrode was almost identical to that of the microcracks located between both electrodes, as previously reported. However, a decrease in the degree of healing was observed near the negative electrode. This was attributed to the insufficient recovery of dislocations generated at the indentation state, which should have occurred in the initial stage of healing. The delay in dislocation recovery prevented contact between the inner surfaces of the microcracks and is possibly related to the increase in oxygen vacancies near the negative electrode.

DOI： 10.1016/j.ceramint.2024.04.251

Variation of surface morphology of material uplift near flash-healed Vickers indents under direct-current electric field in cubic zirconia single crystals 査読有り Open Access

Kayukawa, S; Katsuyama, Y; Tokunaga, T; Yamamoto, T

JOURNAL OF THE CERAMIC SOCIETY OF JAPAN 132 巻 ( 8 ) 頁： 528 - 531 2024年8月

記述言語：英語出版者・発行元：Journal of the Ceramic Society of Japan

Flash events can cause rapid mass diffusion through instantaneous power spikes that occur in electric fields and at temperatures above certain thresholds. Recent research suggests that such mass diffusion caused by the flash event may include athermal effects in addition to Joule heating due to the power spikes. However, this perspective has not been applied to surface diffusion, one of the mass diffusion pathways. This study examines the athermal effect on surface diffusion during the flash event by analyzing the surface morphology variation of material uplift formed after the flash-/thermal-healing of Vickers-indentation-induced microcracks. The results show that the formation of surface facet structures, one of the material uplift surface morphologies, varies depending on the direction of the direct current (DC) electric field. The direction dependence of the facet structure formed on the material up-lifted surface due to the DC electric field is a result of the electric field drift effect. The athermal effects associated with flash events can be considered to exist also in mass diffusion involving surface diffusion.

DOI： 10.2109/jcersj2.24036

Pulsed laser deposition and structural analysis of Ba<sub>2</sub>Ti<sub>6</sub>O<sub>13</sub> epitaxial thin film on the (210) surface of SrTiO<sub>3</sub> single crystal 査読有り Open Access

Kono, R; Hieda, K; Tokunaga, T; Tamura, R; Masamura, R; Hikita, Y; Kano, K; Yamamoto, T

APPLIED PHYSICS EXPRESS 17 巻 ( 7 ) 2024年7月

記述言語：英語出版者・発行元：Applied Physics Express

A single crystalline thin film of Ba2Ti6O13 was grown on the (210) surface of a SrTiO3 single-crystal substrate by pulsed laser deposition. Scanning transmission electron microscopy shows that the Ba2Ti6O13 thin film grew epitaxially with the a-plane, and the b-/c-axes of Ba2Ti6O13 parallel to the (210) plane and the [00 1 ¯ ]/[ 1 ¯ 20] directions of SrTiO3, respectively. The electrical conductance of the Ba2Ti6O13 film was approximately one order larger than that of the reduced SrTiO3−δ single crystal with oxygen deficiency of roughly δ = 0.05. Electronic structure calculations predict that Ba2Ti6O13 is an n-type degenerate semiconductor with spin-split states primarily of Ti 3d orbital.

DOI： 10.35848/1882-0786/ad605d

Phase textures of metal-oxide nanocomposites self-orchestrated by atomic diffusions through precursor alloys 査読有り Open Access

Shudin, NH; Eguchi, R; Fujita, T; Tokunaga, T; Hashimoto, A; Abe, H

PHYSICAL CHEMISTRY CHEMICAL PHYSICS 26 巻 ( 19 ) 頁： 14103 - 14107 2024年5月

記述言語：英語出版者・発行元：Physical Chemistry Chemical Physics

Metal-oxide nanocomposites (MONs) are of pivotal importance as electrode materials, yet lack a guiding principle to tune their phase texture. Here we report that the phase texture of MONs can be tuned at the nanoscale by controlling the nanophase separation of precursor alloys. In situ transmission electron microscopy (in situ TEM) has demonstrated that a MON material of platinum (Pt) and cerium oxide (CeO2) is obtained through promoted nanophase separation of a Pt5Ce precursor alloy in an atmosphere containing oxygen (O2) and carbon monoxide (CO). The Pt-CeO2 MON material comprised an alternating stack of nanometre-thick layers of Pt and CeO2 in different phase textures ranging from lamellae to mazes, depending on the O2 fraction in the atmosphere. Mathematical simulations have demonstrated that the phase texture of MONs originates from a balance in the atomic diffusions across the alloy precursor, which is controllable by the O2 fraction, temperature, and composition of the precursor alloys.

DOI： 10.1039/d3cp05157a

Non-uniformity of shrinkage rate as a function of current acceleration during flash event under voltage-to-current protocol in 8 mol %Y<sub>2</sub>O<sub>3</sub>-ZrO<sub>2</sub> 査読有り Open Access

Seko, M; Inagaki, S; Tokunaga, T; Yamamoto, T

JOURNAL OF THE CERAMIC SOCIETY OF JAPAN 132 巻 ( 3 ) 頁： 93 - 98 2024年3月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of the Ceramic Society of Japan

This study verified the behavior of sample current, volumetric power dissipation, and shrinkage during flash sintering with the voltage-to-current protocol in the time frame of 90 s before and after the flash event. The volumetric power dissipation exhibited a peak value, followed by a decrease to the minimum value, and then increased asymptotically and approached a steady-state value. The discrepancy between the peak and minimum values, ¦P, increased with the limiting current value pre-set at the power supply during the heat-up stage. As ¦P increased, the degree of shrinkage progress decreased in stage III after the flash event, which is caused by the heterogeneity of shrinkage rate inside a compact. To consider the complete shrinkage amount, including stage III, in the current-to-voltage protocol, it is crucial to ensure that ¦P does not reach an excessive level when setting the maximum current.

DOI： 10.2109/jcersj2.23179

DOI： 10.2109/jcersj2.23179

Variation of grain boundary dihedral angles caused by voltage-to-current-based flash treatment in fully stabilized yttria-doped zirconia polycrystals 査読有り

Seko, M; Kayukawa, S; Inagaki, S; Tokunaga, T; Yamamoto, T

JOURNAL OF THE CERAMIC SOCIETY OF JAPAN 132 巻 ( 2 ) 頁： 63 - 67 2024年2月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of the Ceramic Society of Japan

The flash sintering method has garnered attention for its ability to significantly accelerate the densification rate of ceramic green compact through the generation of an electric power spike under an electric field exceeding a defined threshold. In order to amass foundational knowledge about the phenomenon that results from an electric field during flash sintering via a voltage-to-current protocol, the dihedral angles of grain boundaries were surveyed in flash-treated pre-sintered fully stabilized zirconia polycrystal. The flash treatment resulted in a reduction of the grain boundary dihedral angle for grain boundaries that are approximately perpendicular to the direction of the electric field. The reduction in the dihedral angle is possibly attributed to a reduction in surface energy which can be observed through the formation of sinuous pores during flash sintering.

DOI： 10.2109/jcersj2.23170

Effect of Initial Grain Size on Crack Healing Behavior under DC Electric Field of Zirconia (8Y-CSZ) Ceramic 査読有り

Takahashi, S; Morita, K; Nambu, K; Terada, D; Kobayashi, K; Tokunaga, T; Yamamoto, T

ADVANCED ENGINEERING MATERIALS 25 巻 ( 18 ) 2023年9月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Advanced Engineering Materials

The effect of initial grain size on the flash event was examined in microcrack healing behavior under DC electric field in fine- and coarse-grained 8 mol% Y2O3-stabilized cubic ZrO2 (8Y-CSZ) polycrystals. The healing behavior depends strongly on the initial grain size and is apparently accelerated in fine-grained 8Y-CSZ than in coarse-grained one. Since the crack healing under the flash event is higher than that of static annealing treatment without the electric field, the enhanced healing phenomena cannot be explained only by the thermal effect caused by Joule heating, but nonthermal effects caused by the flash event. The grain size-dependent healing behavior indicates that the grain boundaries play an important role in the flash event and the flash healing would be accelerated through the field/current-enhanced diffusional processes, especially through the grain boundary diffusivity of the cations.

DOI： 10.1002/adem.202201807

DOI： 10.1002/adem.202201807

Layer transfer of ultrathin Ge crystal segregated on Al/Ge(111) structure 査読有り

Matsushita, K; Ohta, A; Shibayama, S; Tokunaga, T; Taoka, N; Makihara, K; Miyazaki, S

JAPANESE JOURNAL OF APPLIED PHYSICS 62 巻 ( SG ) 2023年6月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Japanese Journal of Applied Physics

Effects of the surface modification by O2 plasma exposure on the Al/Ge(111) structure have been investigated in order to get an insight into a layer transfer technique of the ultrathin Ge layer segregated on the Al/Ge(111) structure toward the device fabrication, and then the wafer bonding of the Al/Ge(111) structure to the thermally-grown SiO2/Si structure has been demonstrated. The O2 plasma treatment and the subsequent pure water rinse were found to be effective to form the hydrophilic surface of the Al/Ge(111) structure with a suppression of the segregated Ge layer oxidation. The Al/Ge(111) structure with the hydrophilic surface was then bonded to the SiO2/Si substrate, and its bonding strength was enough to perform Ge thinning by the chemical mechanical polishing and the wet-chemical etching using H2O2-based solutions. Ohmic contact of the ring-type device pattern with the segregated Ge/Al stack was achieved by using the remaining p-type Ge substrate as the contact pads.

DOI： 10.35848/1347-4065/acb65c

DOI： 10.35848/1347-4065/acb65c

Scanning electron microscopy observation in wide field of view for SrO/TiO2-terminated step-terrace structure formed on SrTiO3(001) single crystal surface 査読有り

Katsuyama, Y; Kodaira, A; Tokunaga, T; Yamamoto, T

JOURNAL OF THE CERAMIC SOCIETY OF JAPAN 131 巻 ( 5 ) 頁： 135 - 139 2023年5月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of the Ceramic Society of Japan

SrO-terminated terraces were formed along TiO2-terminated step edges by annealing (001) surfaces of SrTiO3 single crystal originally with step-terrace structure fully terminated at TiO2 atomic layer. The prepared step-terrace structure with the two different terminations were visualized in a wide field of view using scanning electron microscopy (SEM) under a low acceleration voltage of 1 kV and a short working distance of 2 mm. The different termination was clearly identified by an in-column secondary electron detector even in the wide-field region with dimensions of 30 © 30 ¯m2. As results, the uniformity of the step-terrace structure was found to be limited only at a localized area. The wide-field observation revealed that there exist many “step-defects” such as pinning of the step lines and wandering so large that it goes around to an opposite side. Step-defects were present in at least several for 30 © 30 ¯m2 sized observation areas with a probability of about 60 %.

DOI： 10.2109/jcersj2.23011

DOI： 10.2109/jcersj2.23011

Local Crystallization of Amorphous Aluminum Oxide Thin Film Using Electron Beam Irradiation by SEM

Tanahashi, S; Okawara, S; Tokunaga, T; Yamamoto, T

MATERIALS TRANSACTIONS 64 巻 ( 1 ) 頁： 184 - 190 2023年

Shrinkage-rate controlled flash sintering for 3-10 mol %Y<sub>2</sub>O<sub>3</sub>-doped ZrO<sub>2</sub> polycrystals 査読有り

Koike, M; Kodaira, A; Tokunaga, T; Yamamoto, T

JOURNAL OF THE CERAMIC SOCIETY OF JAPAN 130 巻 ( 12 ) 頁： 906 - 912 2022年12月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of the Ceramic Society of Japan

Shrinkage-rate controlled flash (SCF) sintering using alternative current electric field was systematically performed for 310 mol% Y2O3-doped ZrO2. As results, the uniformly densified compacts with about 99% relative densities could be produced at furnace temperatures of about 754781 °C for about 30 min as SCF-regime irrespective of Y concentration, while the achieved densities were limited by conventional flash sintering. The shrinkage-rates during SCF-sintering were found to be enhanced in lower temperature range comparing those during thermal-sintering. The enhancement of shrinkage-rates in lower temperature range observed in SCFsintering is possibly related to the reduction of apparent activation energy of sintering under electric fields.

DOI： 10.2109/jcersj2.22114

Shell-like structure to limit further densification formed during flash sintering under alternative current electric field for 8 mol %Y2O3-doped ZrO2 査読有り

Seko, M; Hattori, K; Ishino, Y; Kodaira, A; Tokunaga, T; Yamamoto, T

JOURNAL OF THE CERAMIC SOCIETY OF JAPAN 130 巻 ( 11 ) 頁： 895 - 898 2022年11月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of the Ceramic Society of Japan

A phenomenon often appears that the final achieved density is limited during conventional flash sintering even under alternative current electric field. By observing the cross-sectional microstructure of the flash sintered 8 mol %Y2O3-doped ZrO2 at this state, we found that a thin surface portion with near full density surrounds a porous inside with lower density. The densified thin surface portion is shell-like structure covering a whole of the sintered compact. The formation of this characteristic shell-like structure in the early stage of flash sintering greatly restricts subsequent densification of porous inside. In order to suppress the formation of the shell that inhibit densification, a technique of controlling a steep power spike at a flash event must be necessary to be appropriately transitioned.

DOI： 10.2109/jcersj2.22109

A first attempt of automated shrinkage-rate control flash sintering using a current profile without feedback of shrinkage behavior for 8 mol % Y<sub>2</sub>O<sub>3</sub> -doped ZrO<sub>2</sub> 査読有り

Koike, M; Ishino, Y; Tokunaga, T; Yamamoto, T

JOURNAL OF THE CERAMIC SOCIETY OF JAPAN 130 巻 ( 4 ) 頁： 327 - 330 2022年4月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of the Ceramic Society of Japan

Shrinkage-rate control flash (SCF) sintering is an attractive flash sintering that is modified to densify ceramic green compacts up to high density, which controls electric current to keep shrinkage-rate constant by feedback from shrinkage behavior during a flash state. To build up easier sintering protocol and to realize faster shrinkage-rate, we attempted automated SCF-sintering using the predicted current profile without feedback of the shrinkage behavior. As results, 8YSZ polycrystal with a density of 5.83 g/cm3 and a grain size of 1.84.5 μm could be produced within 10 min during SCF and soaking regimes at the furnace temperature of 870 °C, although the linearity of shrinkage-rate during automated SCF-sintering is degraded from the assumed shrinkage-rate. In order to improve automated SCF-sintering further, a more accurate method of approximating the current profile would be necessary to realize the higher linearity of shrinkage-rate.

DOI： 10.2109/jcersj2.22009

Crystalline boron monosulfide nanosheets with tunable bandgaps 査読有り

Kusaka, H; Ishibiki, R; Toyoda, M; Fujita, T; Tokunaga, T; Yamamoto, A; Miyakawa, M; Matsushita, K; Miyazaki, K; Li, LH; Shinde, SL; Lima, MSL; Sakurai, T; Nishibori, E; Masuda, T; Horiba, K; Watanabe, K; Saito, S; Miyauchi, M; Taniguchi, T; Hosono, H; Kondo, T

JOURNAL OF MATERIALS CHEMISTRY A 9 巻 ( 43 ) 頁： 24631 - 24640 2021年11月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of Materials Chemistry A

Two-dimensional (2D) boron monosulfide (BS) nanosheets are predicted to have several stable phases and unique electronic structures, endowing them with interesting attributes, including superconducting, thermoelectric, and hydrogen storage properties. In this paper, we report the experimental realization of 2D BS nanosheets by the physical exfoliation of rhombohedral boron monosulfide (r-BS). Moreover, we demonstrate the facile separation of a mixture of 2D BS nanosheets and the r-BS powder in acetonitrile; the former were selectively separated as a dispersion in the supernatant, whereas the latter remained in the precipitate. In addition, density functional theory calculations reveal a clear dependence of the bandgap energy (Eg) on the number of layers of stacked BS nanosheets, whereEgfor BS nanosheets is approximately 1.0 eV higher than that for r-BS. Atomic force microscopy, cathode luminescence, ultraviolet-visible absorption spectroscopy, and excitation emission matrix experiments revealed a consistent bandgap difference of approximately 1.0 eV between the BS nanosheets and r-BS. We also demonstrate the applications based on the properties that originated from the difference in the bandgap between r-BS and BS nanosheets using photoelectrochemical current switching. These results indicate that the nanosheet bandgap can be tuned to a desired value by controlling the number of stacked 2D BS nanosheets. Therefore, BS nanosheets are promising non-metal 2D materials for applications requiring bandgap control, such as electronics and photocatalysis.

DOI： 10.1039/d1ta03307g

Shrinkage rate control during a flash state by current-ramping for 3 mol% Y<sub>2</sub>O<sub>3</sub>-doped ZrO<sub>2</sub> polycrystals 査読有り

Ishino, Y; Taguchi, K; Koike, M; Tokunaga, T; Yamamoto, T

JOURNAL OF THE AMERICAN CERAMIC SOCIETY 104 巻 ( 10 ) 頁： 4960 - 4967 2021年10月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of the American Ceramic Society

3 mol% Y2O3-doped ZrO2 green compacts with rectangular shapes were sintered by maintaining the shrinkage rates at constant values under alternating electric fields by ramping the electric current during flash states. Green compacts were furnace-heated under 40-100 Vrms/cm until current hits an initial current limit of 100 mArms. After then, current-ramping was started to keep the shrinkage rates constant by increasing the limit current value using a programmable power supply operating in a current control mode. Highly densified 3 mol% Y2O3-doped ZrO2 polycrystals with a density of 6.05 g/cm3 as a bulk density and a grain size of about 0.4 μm were obtained at a furnace temperature of about 930℃, 50 Vrms/cm with 1000 Hz and shrinkage rate of about 120 μm/min (0.8%/min against initial lengths of green compacts). The Vickers hardness and indentation fracture toughness of the compact exhibit similar values to those obtained from thermally sintered compacts.

DOI： 10.1111/jace.17912

Rapid sintering of 3 mol % Y<sub>2</sub>O<sub>3</sub>-doped ZrO<sub>2</sub> by a combined rapid furnace heating and shrinkage-controlled flash sintering protocol 査読有り

Ishino, Y; Taguchi, K; Kodaira, A; Tokunaga, T; Yamamoto, T

JOURNAL OF THE CERAMIC SOCIETY OF JAPAN 129 巻 ( 8 ) 頁： 551 - 554 2021年8月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of the Ceramic Society of Japan

Flash sintering has attracted much attention as a useful sintering technique that is able to lower the sintering furnace temperature and shorten the sintering time. To further improve this original flash sintering technique, we have developed a technique to facilitate shrinkage at a constant shrinkage rate by controlling the power dissipation during a flash state, which is termed as shrinkage-controlled flash (SCF) sintering. Here, we combine this SCF sintering method with a rapid furnace heating process to shorten the entire sintering process time. Accordingly, we succeed in sintering 3 mol % Y2O3-doped ZrO2 (3YSZ) polycrystals with a high density of 6.05 g/cm3 and a uniform grain size of approximately 0.47 μm with a short sintering time of approximately 40 min. The obtained 3YSZ polycrystals are confirmed to exhibit a Vickers hardness and fracture toughness [by an indentation fracture method] of approximately 1295 HV and 5.3 MPa m1/2, respectively.

DOI： 10.2109/jcersj2.21066

Near complete densification of flash sintered 8YSZ: controlled shrinkage rate effects 査読有り

Taguchi, K; Ishino, Y; Tokunaga, T; Yamamoto, T

JOURNAL OF THE EUROPEAN CERAMIC SOCIETY 41 巻 ( 8 ) 頁： 4567 - 4571 2021年7月

記述言語：英語出版者・発行元：Journal of the European Ceramic Society

Rate-controlled sintering of 8 mol%Y2O3-doped ZrO2 (8YSZ) polycrystals was performed by rating the current limit of alternating current (AC) electric field during a flash event; this method promotes constant linear shrinkage of the green compact with respect to the sintering time. A power dissipation peak associated with the flash event was suppressed by setting the initial current limit at 100 mA; after AC current hits 100 mA, the current limit was rated to a maximum value of 1100−2000 mA to keep shrinkage rate constant. The power dissipation behavior during the current-rating process exhibited a characteristic inverted S-shaped curve as a function of time. 8YSZ polycrystal with a near-theoretical density of 5.97 g/cm3 and a grain size of approximately 3.4 μm was produced in AC electric field (150 V/cm at 1000 Hz) with a final maximum current limit of 1150 mA as a rectangular bulk style.

DOI： 10.1016/j.jeurceramsoc.2021.03.005

Constant shrinkage rate control during a flash event for 8 mol%Y<sub>2</sub>O<sub>3</sub>-doped ZrO<sub>2</sub> polycrystals 査読有り

Taguchi, K; Ishino, Y; Tokunaga, T; Yamamoto, T

JOURNAL OF THE CERAMIC SOCIETY OF JAPAN 129 巻 ( 3 ) 頁： 204 - 207 2021年3月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of the Ceramic Society of Japan

The shrinkage rate during a flash event is controlled at a constant value by current ramping for 8 mol %Y2O3ZrO2 green compact with a rectangular shape. The green compact is heated at a constant heating rate of 5 °C/min until the occurrence of a flash event under a constant alternative current (AC) field of 50 Vrms/cm and 1000 Hz at a limit current of 100 mArms. After the flash event, current ramping is started to keep the shrinkage rate at a constant value of 120 ¯m/min. Current ramping is conducted by controlling the limit current using a programmable power supply operating in a current control mode. When the limit current reaches 1200 mArms, the sintering condition is kept as it is for 5 min, and the sintering process is completed. 8 mol %Y2O3ZrO2 sintered polycrystal with a relative density of approximately 99 % and a grain size of about 2.5 ¯m can be obtained at a furnace temperature of 870 °C for a current ramping and soaking regime of approximately 30 min.

DOI： 10.2109/jcersj2.20192

Power Dissipation Behaviors during SCF-sintering for 8 mol% Y<inf>2</inf>O<inf>3</inf>-doped ZrO<inf>2</inf>

Ishino Y., Taguchi K., Kodaira A., Tokunaga T., Yamamoto T.

Funtai Oyobi Fummatsu Yakin/Journal of the Japan Society of Powder and Powder Metallurgy 68 巻 ( 11 ) 頁： 482 - 486 2021年

出版者・発行元：Funtai Oyobi Fummatsu Yakin/Journal of the Japan Society of Powder and Powder Metallurgy

Shrinkage behaviors during shrinkage rate-controlled flash (SCF) sintering were investigated for 8 mol% Y2O3–ZrO2 (8YSZ) when shrinkage rates were varied between 60 and 300 μm/min under alternating current fields of 50 Vrms/cm, 1200 mArms, and 1000 Hz at a furnace temperature of approximately 870°C. Volumetric power dissipation and electrical conductivity were shown to exhibit similar dependencies against linear shrinkages even if the shrinkage rates were changed. The 8YSZ polycrystals, with similar microstructure and density, could be produced under all SCF conditions used in this study, which was confirmed as a characteristic feature of SCF sintering. Finally, the 8YSZ polycrystals with a density of 5.91–5.93 g/cm3 and a grain size of 2.2–2.6 μm could be produced with a shrinkage process period of 15–65 min at a furnace temperature of approximately 870°C.

DOI： 10.2497/jjspm.68.482

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