Transparent Sintered Corundum with High Hardness and Strength

Krell, Andreas; Blank, Paul S.; Ma, Hongwei; Hutzler, Thomas; Bruggen, M.P.B. van; Apetz, R.

doi:10.1111/j.1151-2916.2003.tb03270.x

Cited by 291 publications

(231 citation statements)

References 13 publications

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“…By this method no light scattered by more than 1.2 • will reach the detector. As this is the maximum angle (border to border), this method can be assumed to be comparable to the laser RIT measurement (<0.5 • ) described by Krell et al 3 Note that without shields, the inline transmittance measurement would include more scattered light and therefore the RIT would appear higher.…”

Section: Materials and Experimental Methodsmentioning

confidence: 99%

“…Doping was carried out by dispersing 25 g of the powder in 60 mL 0.01 M HNO 3 and adding the required dopant solutions Mg(NO 3 …”

Section: Materials and Experimental Methodsmentioning

confidence: 99%

“…For post-HIP treated samples, results for undoped, 5 singledoped (Mg 2+ , Ti 4+ ) 1,3,9 and co-doped (Ca 2+ -Ti 4+ ) 10 PCA have been reported so far. This method gave fairly reproducible RITs between different groups with values up to 65%.…”

Section: Introductionmentioning

confidence: 99%

“…Over recent years, attempts have been made to replace sapphire by transparent polycrystalline alumina (PCA) [1][2][3][4][5][6] for both economic and ecological reasons.…”

Section: Introductionmentioning

confidence: 99%

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Transparent polycrystalline alumina using spark plasma sintering: Effect of Mg, Y and La doping

Stuer

Zhao

Aschauer

et al. 2010

Journal of the European Ceramic Society

110

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Transparent polycrystalline alumina (PCA) is a promising replacement for sapphire. Its optical properties however are highly dependent on the grain size and residual porosity which need to be controlled for real inline transmittances (RIT), that are high enough for possible applications.To achieve high RITs, doping as well as pressure assisted sintering is often used. In this study spark plasma sintering (SPS) and doping are investigated. A systematic experimental design is used to study the influence of Mg, Y and La single or co-doping (75-450 ppm) as well as the SPS sintering pressure and temperature on the RIT and grain size of PCA.Using optimized sintering parameters, RITs of >50% were attained in the visible wavelength (640 nm) for 0.8 mm thick samples for almost all doping strategies. The best RIT of 57% was for triple-doped samples at a total dopant level of 450 ppm. These results are significantly better than previously published SPS studies and illustrate that SPS sintered alumina can attain high and reproducible optical transmittances under various doping and sintering conditions.

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Section: Materials and Experimental Methodsmentioning

confidence: 99%

“…Doping was carried out by dispersing 25 g of the powder in 60 mL 0.01 M HNO 3 and adding the required dopant solutions Mg(NO 3 …”

Section: Materials and Experimental Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

“…Over recent years, attempts have been made to replace sapphire by transparent polycrystalline alumina (PCA) [1][2][3][4][5][6] for both economic and ecological reasons.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Transparent polycrystalline alumina using spark plasma sintering: Effect of Mg, Y and La doping

Stuer

Zhao

Aschauer

et al. 2010

Journal of the European Ceramic Society

110

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“…As the grain size of fully dense alumina is reduced, significant benefits are observed in terms of improved mechanical properties [1,2], superior wear resistance [3] and optical transparency [4]. To obtain dense submicron-grained or nanocrystalline alumina ceramics (NCAs), studies on the densification of alumina have focused on the use of nanosized transition alumina powders as a starting powder [5,6].…”

Section: Introductionmentioning

confidence: 99%

Fabrication of submicron alumina ceramics by pulse electric current sintering using M2+ (M=Mg, Ca, Ni)-doped alumina nanopowders

Odaka¹,

Yamaguchi²,

Hida³

et al. 2009

Ceramics International

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Dense submicron-grained alumina ceramics were fabricated by pulse electric current sintering (PECS) using M 2+ (M: Mg, Ca, Ni)-doped alumina nanopowders at 1250°C under a uniaxial pressure of 80 MPa. The M 2+ -doped alumina nanopowders (0-0.10 mass%) were prepared through a new sol-gel route using high-purity polyhydroxoaluminum (PHA) and MCl2 solutions as starting materials. The composite gels obtained were calcined at 900°C and ground by planetary ball-milling. The powders were re-calcined at 900°C to increase the content of α-alumina particles, which act as seeding for low-temperature densification. Densification and microstructural development depend on the M 2+ dopant species. Dense alumina ceramics (relative density ≥ 99.0%) thus obtained had a uniform microstructure composed of fine grains, where the average grain size developed for non-doped, Ni-doped, Mg-doped and Ca-doped samples was 0.67, 0.67, 0.47 and 0.30 m, respectively, showing that Ca-doping is the most promising method for tailoring of nanocrystalline alumina ceramics.Keywords: A. Sintering; A. Sol-gel processes; B. Grain size; D. Al2O3 3 IntroductionAs the grain size of fully dense alumina is reduced, significant benefits are observed in terms of improved mechanical properties [1,2], superior wear resistance [3] and optical transparency [4]. To obtain dense submicron-grained or nanocrystalline alumina ceramics (NCAs), studies on the densification of alumina have focused on the use of nanosized transition alumina powders as a starting powder [5,6]. In these studies, transition aluminas were densified by hot-pressing [5] or sinter-forging [6], and alumina ceramics with an -alumina grain size of 200 nm or less were obtained. We have also focused on the use of transition alumina powders and attempted densification by pulse electric current sintering (PECS) using polyhydroxoaluminum (PHA) gel-derived γ-alumina powders [7][8][9]. As a result, we obtained fully densified alumina ceramics with a relatively high bending strength of ~860 MPa under optimized conditions [9]. However, these alumina ceramics showed an inhomogeneous microstructure consisting of submicron-sized grains and a large number of elongated large grains due to the presence of impurities such as CaO and SiO2.It is well known that additives such as , CaO [14,15] and NiO [11] affect the sintering behavior of -alumina. MgO plays a particularly beneficial role in inhibiting grain growth of -alumina, which can be explained in terms of a solute drag (pinning) model [11,12]. While the effect of MO (M: Mg, Ca, Ni) addition to -alumina powders on grain growth inhibition has been studied extensively, there are few reports concerning the effects of M 2+ -doping on densification of γ-aluminas except for Mg 2+ -doping [16]. In particular, systematic studies on the densification behavior induced by PECS for various M 2+ -doped γ-alumina powders, in which M 2+ cations are substituted into the crystal lattice of γ-alumina, have been lacking.Thus, the present study extends the potentia...

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The Influence of Minor Additives on Densification and Microstructure of Submicrometer Alumina Ceramics Prepared by SPS and HIP

Sedláček

Michalková

Karaman³

et al. 2009

Ceramic Transactions Series

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Transparent Sintered Corundum with High Hardness and Strength

Cited by 291 publications

References 13 publications

Transparent polycrystalline alumina using spark plasma sintering: Effect of Mg, Y and La doping

Transparent polycrystalline alumina using spark plasma sintering: Effect of Mg, Y and La doping

Fabrication of submicron alumina ceramics by pulse electric current sintering using M2+ (M=Mg, Ca, Ni)-doped alumina nanopowders

The Influence of Minor Additives on Densification and Microstructure of Submicrometer Alumina Ceramics Prepared by SPS and HIP

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