Preparation and Properties of Large-Sized Sapphire Crystal by Edge-Defined Film-Fed Growth Method

doi:10.16553/j.cnki.issn1000-985x.2025.0182

Abstract

Abstract: Modern high-tech warfare imposes stringent requirements on armored equipment，demanding the integration of visualization，superior ballistic resistance，lightweight design，and high maneuverability. Sapphire crystals have emerged as a preferred candidate for novel transparent armor systems，attributed to their exceptional optical，mechanical，thermal properties，and robust corrosion resistance. Constrained by limitations in crystal size and manufacturing costs in the early stages，sapphire crystals were predominantly confined to small-scale components such as fairings and face shields. With the advancement of crystal growth technologies，particularly the edge-defined film-fed growth （EFG） method，the fabrication and practical application of large-sized sapphire plates have been successfully realized both domestically and internationally.In this study，large-sized sapphire crystals with dimensions of 486 mm×1 000 mm×12 mm were successfully fabricated for the first time using a self-designed large-scale EFG furnace，and their comprehensive performance was systematically characterized. Double-crystal rocking curve measurements via X-ray diffractometer reveals a symmetric peak profile with a full width at half maximum （FWHM） of merely 20.53″，indicating excellent lattice integrity of the as-grown sapphire crystals. Corrosion tests were conducted on samples extracted from different regions of the sapphire crystal using molten KOH；the observation of neat and regular dislocation morphologies enabled the estimation of dislocation density at the magnitude of 103. Surface elemental analysis via energy dispersive spectrometer （EDS） demonstrates the high purity and homogeneous composition of the crystals，with no detectable incorporation of impurity elements such as Mo or C during the growth process. Stress characterization was performed utilizing a large-aperture birefringence stress testing system，with comparative analyses against sapphire crystals prepared by the Kyropoulos method and the conventional single-thermal-field EFG furnace. The results indicate that the stress level of the sapphire crystals prepared in this work is comparable to that of Kyropoulos-grown crystals，and nearly one order of magnitude lower than that of crystals fabricated by the traditional single-thermal-field EFG furnace. Mechanical property tests via a universal electronic testing machine verified that the sapphire plates exhibit outstanding bending strength and elastic modulus，coupled with excellent performance uniformity across the entire sample.In conclusion，the large-sized sapphire crystals prepared by the self-designed large-scale EFG furnace demonstrate superior comprehensive performance，rendering them an optimal material for large-sized transparent armor applications. This research not only lays a solid material foundation for the independent research and development，and engineering application of a new generation of high-performance armored equipment，but also holds profound strategic significance and substantial engineering practical value for the advancement of national defense materials technology.

Key words: sapphire crystal; edge-defined film-fed growth method; X-ray rocking curve; dislocation; stress; bending strength; elastic modulus

CLC Number:

O786

LI Qinglian, SUN Jun, ZHAO Chencheng, LIU Ziqi, XU Jingjun, WANG Xiaoliang, ZHAO Peng, WANG Yubao, HUANG Cunxin. Preparation and Properties of Large-Sized Sapphire Crystal by Edge-Defined Film-Fed Growth Method[J]. Journal of Synthetic Crystals, 2026, 55(2): 274-280.

Figures/Tables 7

Fig.1 Schematic diagram of sapphire samples sampling

Fig.2 Double-crystal X-ray rocking curve of 2#

Fig.3 Photo of dislocation etch pits of samples

Fig.4 SEM images of dislocation etch pits of samples

Fig.5 EDS of samples

Fig.6 Stress distribution of sapphire crystals

Table 1 Bending strength and elastic modulus of sapphire crystals

Sample	1#2	2#2	3#2	MgAl₂O₄^［17］	AlNO^［17］
Bending strength/MPa	759	763	758	175	380~700
Elastic modulus/GPa	442	453	466	273	334

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