Fabrication of Magnesium-Aluminate Spinel Transparent Ceramics by Two Cycles of Hot Pressing Sintering Method

doi:10.16553/j.cnki.issn1000-985x.2025.0174

Abstract

Abstract: In this study， high-purity （99.999%） magnesium-aluminate spinel （MgAl₂O₄） powder was used to fabricate transparent magnesium-aluminate spinel ceramics through a two cycles of hot pressing sintering method combined with hot isostatic pressing （HIP）. The first hot pressing was conducted at a relatively low temperature using a hot pressing mold， while the second hot pressing step was performed at a higher temperature without a mold. The morphology of the powder and the fracture surface of the ceramic samples were observed using SEM， and the optical transmittance of the ceramics were measured. Compared to conventional hot pressed transparent ceramics， the samples prepared by two cycles of hot pressing sintering exhibit slight differences in their fracture surface microstructure， while their transmittance remains comparable. The ceramics exhibit transmittance exceeding 80% over most wavelengths from visible to mid-wave infrared spectrum. The two cycles of hot pressing sintering method enables the production of larger transparent ceramics using relatively small hot pressing molds and equipment.

Key words: magnesium-aluminate spinel; transparent ceramics; two cycles of hot pressing sintering; hot pressing mold; morphology; optical transmittance; larger size

CLC Number:

TQ174.75

LEI Muyun, WANG Ying, LING Hao, WANG Haili, LI Zhen, ZHANG Lisheng. Fabrication of Magnesium-Aluminate Spinel Transparent Ceramics by Two Cycles of Hot Pressing Sintering Method[J]. Journal of Synthetic Crystals, 2026, 55(1): 85-92.

Figures/Tables 8

Table 1 Impurity content of magnesia-aluminum spinel powder

Element	Concentration（mass fraction）/ppm	Element	Concentration（mass fraction）/ppm
O	Martix	Co	<0.05
Na	1.1	Ni	<0.5
Mg	Martix	Cu	0.29
Al	Martix	Zn	0.49
Si	1.7	Ce	<0.5
K	<0.05	Pr	<0.1
Ca	0.73	Nd	<0.1
Mn	0.98	Eu	<0.1
Fe	1.0	Ta	Electrode

Fig.1 SEM images of powders before and after granulation， along with optical micrograph

Fig.2 Statistical data particle size distribution and particle size curves of powders before granulation

Fig.3 SEM-EDS of powders after ball-milled with LiF additive

Fig.4 Photographs of transparent ceramic samples. （a） ?67 mm sample fabricated by conventional hot pressing；（b） ?92 mm sample prepared by two cycles of hot pressing

Fig.5 Transmission curves of magnesium-aluminate spinel transparent ceramics

Fig.6 Fracture surface of magnesium-aluminate spinel transparent ceramics prepared by conventional method

Fig.7 SEM images of fracture surfaces of MgAl?O? transparent ceramics prepared by two cycles of hot pressing sintering method

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