Rapid pressure-less sintering of fine grained zirconia ceramics: Explanation and elimination of a core-shell structure

Prajzler, Vladimír; Průša, Stanislav; Maca, Karel

doi:10.1016/j.jeurceramsoc.2019.07.053

Cited by 15 publications

(7 citation statements)

References 36 publications

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“…This rapid consolidation would cause the formation of a so-called core-shell structure characterized by a fully dense surface layer and high inner porosity [48]. Our SEM micrographs, on the other hand, did not reveal the presence of pores, voids or other structural defects regardless the type of sintering method, which might be regarded notably for the investigated speed sintering.…”

Section: Discussionmentioning

confidence: 51%

Mechanical properties, aging stability and translucency of speed-sintered zirconia for chairside restorations

et al. 2020

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Objectives: To evaluate the performance of zirconia ceramics sintered in a speed sintering induction furnace by comprehensive understanding of their optical and mechanical properties, microstructure, phase composition and aging stability, in comparison to ceramics sintered in a conventional furnace.Methods: Speed sintered (SS) Katana STMLSS (Kuraray Noritake) (total thermal cycle/sintering time/dwell temperature: 30 min/16 min/1560 °C) and CEREC Zirconia (CEREC ZrSS) (Dentsply Sirona) (15 min/2 min/1578 °C) were compared to conventionally sintered (CS) Katana STMLCS (6.8 h/2 h/1550 °C) and inCoris TZICS (4 h/2 h/1510 °C). The translucency Parameter (TP) and Contrast Ratio (CR)were measured with a spectrophotometer. The chemical composition of the materials was determined by XRF and phase composition was characterized using XRD. Hydrothermal aging behavior was evaluated by measuring the tetragonal-to-monoclinic ZrO2 phase transformation after accelerated hydrothermal aging in steam at 134°C. The indentation fracture toughness, Vickers hardness and biaxial strength of the sintered ceramics were assessed.Results: Speed and conventionally sintered zirconia revealed similar density, microstructure, average strength and hydrothermal aging stability. Both Katana STMLSS/CS 5Y-PSZ ceramics were characterized with a higher content of cubic phase (≈53 wt%), which resulted in a higher amount of Y2O3 in the remaining tetragonal ZrO2 phases compared to the 3Y-TZP CEREC ZrSS and inCoris TZICS (8 wt% and 20 wt%, respectively). The sintering program did not affect the hydrothermal aging behavior of Katana STMLSS and CEREC ZrSS. TP of Katana STMLSS (TP≈32) was not affected by speed sintering, while the translucency of CEREC ZrSS (TP=14) was significantly reduced. Hardness, fracture toughness and Weibull characteristic strength of Katana STMLSS and CEREC ZrSS also reached the optimal level, but speed sintering substantially lowered their mechanical reliability.Significance: Speed sintering of 3Y-TZP and 5Y-PSZ in a speed sintering induction oven appeared suitable for clinical applications. However, further studies should focus on improving of translucency and mechanical reliability of the speed-sintered zirconia ceramics.

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Section: Discussionmentioning

confidence: 51%

Mechanical properties, aging stability and translucency of speed-sintered zirconia for chairside restorations

et al. 2020

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“…The common agreement is that the ultrafast densification is mainly initiated by rapid Joule heating, similar to the rapid densification caused by a high heating rate during fast firing. 3 However, although the fast firing can produce a uniform microstructure without grain size gradients even in relatively large 3YSZ samples, 4,5 the direct electric current (DC) utilized by the FS is responsible for additional effects that have a considerable impact on the grain growth kinetics.…”

Section: Introductionmentioning

confidence: 99%

Abnormal grain growth in DC flash sintered 3‐mol% yttria‐stabilized zirconia ceramics

et al. 2022

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The origin of nonuniform microstructure and abnormal grain growth (AGG) was investigated in flash sintered 3 mol% yttria‐stabilized zirconia (3YSZ) ceramics. The microstructural homogeneity decreased with increasing direct current (DC) density and with dwell time in a flash state, eventually resulting in AGG in the specimen core, the first observation of AGG in 3YSZ. Abnormal grains up to 100 μm in size emerged when the DC density was ≥160 mA/mm2, and the specimen's density exceeded 99% of theoretical, starting from the cathode and propagating toward the anode. The results are discussed by comparison with established mechanisms and previous experimental evidence concerning AGG in oxides, focusing on the possible effects of the electrochemical reduction at the cathode end of the specimen.

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“…The alternative to SPS and MWS could be a technique known as fast firing, [18][19][20][21][22][23][24] sometimes also called rapid sintering, 25 fast sintering, 26 rapid rate sintering, 27 or rapid pressureless sintering (RPLS). 14,[28][29][30] In this study, we use the term RPLS, which emphasizes that there is no external pressure applied during the sintering process. The RPLS utilizes fast heating and cooling rates in the order of magnitude of hundreds • C/min, which can be comparable to those used in SPS 14 and MWS 15 but does not suffer from the mentioned disadvantages.…”

Section: Introductionmentioning

confidence: 99%

“…As reported previously, infrared radiation is dominant over convection and conduction during rapid heating, 28 leading to accelerated microstructure evolution, both in terms of densification and grain growth. So far, the RPLS was mainly tested on structural ceramics, such as alumina and zirconia [18][19][20]25,[27][28][29][30] with only few studies dedicated to piezoelectric ceramics such as PZT [21][22][23][24] and BaTiO 3 . 26 If the same heat transfer mechanism is applicable also for piezoceramic materials, the microstructures comparable to those obtained by CS can be achieved, but in a much shorter time, and resulting in comparable functional properties.…”

Section: Introductionmentioning

confidence: 99%

“…The alternative to SPS and MWS could be a technique known as fast firing, 18–24 sometimes also called rapid sintering, 25 fast sintering, 26 rapid rate sintering, 27 or rapid pressureless sintering (RPLS) 14,28–30 . In this study, we use the term RPLS, which emphasizes that there is no external pressure applied during the sintering process.…”

Section: Introductionmentioning

confidence: 99%

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Rapid pressureless sintering of barium titanate–based piezoceramics and their electromechanical harvesting performance

et al. 2022

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The innovative method of processing of Ba0.85Ca0.15Zr0.1Ti0.9O3 (BCZT), Ba0.95Ca0.05Ti0.91Sn0.09O3 (BCST), and BCZT doped with 0.07‐wt.% CeO2 (Ce‐BCZT) lead‐free piezoceramics is presented. The rapid pressureless sintering (RPLS) technique can reduce high‐temperature processing time more than eight times compared to the conventional sintering. RPLS was performed at a heating and cooling rate of 100°C/min up to 1550°C with 15‐, 30‐, 45‐, and 60‐min dwell times, producing defect and crack‐free nearly dense ceramics. The optimal microstructure exhibiting the highest piezoelectric constant was reached after 30 min in BCZT (grain size 25–30 μm, d33 = 428 pC/N), 45 min in Ce‐BCZT (grain size 30–35 μm, d33 = 515 pC/N), and 45 min of dwell time in BCST (grain size 58–68 μm, d33 = 443 pC/N). The highly competitive energy‐harvesting properties were discovered for BCZT, resp. Ce‐BCZT (ƞ = 94.5, resp. 93.4%, FOMoff = 6.1, resp. 7.8 × 10−10 m2/N) ceramics.

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Rapid pressure-less sintering of fine grained zirconia ceramics: Explanation and elimination of a core-shell structure

Cited by 15 publications

References 36 publications

Mechanical properties, aging stability and translucency of speed-sintered zirconia for chairside restorations

Mechanical properties, aging stability and translucency of speed-sintered zirconia for chairside restorations

Abnormal grain growth in DC flash sintered 3‐mol% yttria‐stabilized zirconia ceramics

Rapid pressureless sintering of barium titanate–based piezoceramics and their electromechanical harvesting performance

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