NL2028094B1 - Vitrification method for enhancing transmittance of surface-unpolished sapphire - Google Patents

Abstract

The present disclosure discloses a vitrification method for enhancing transmittance of surface-unpolished sapphire and a production process thereof. In the vitrification, the 5 following glass components are added, in molar percentage: 10% to 30% of RE203 (RE = Y, La, Gd, and Ce) and 70% to 90% of SiOz, and unpolished sapphire is used. The rare earth RE203 and SiOz are thoroughly mixed and then uniformly spread on the surface of the unpolished sapphire, with a thickness above 1 mm, the sapphire is incubated in a high-temperature furnace at l,400°C to 1,600°C for more than 2 h and 10 then cooled to room temperature in the furnace, and the sapphire is taken out and tested to finally obtain desired sapphire with significantly-increased transmittance, which can be used in the fields of infrared optics, light-emitting diode (LED) substrates, photoelectric displays, military industry, lenses, and the like.

Description

VITRIFICATION METHOD FOR ENHANCING TRANSMITTANCE OF SURFACE-UNPOLISHED SAPPHIRE

TECHNICAL FIELD The present disclosure relates to a vitrification method for enhancing transmittance of surface-unpolished sapphire, and specifically to surface vitrification of unpolished sapphire, which reduces a manufacture cost and greatly improves the optical transmittance of sapphire, so that sapphire becomes an indispensable key component in industrial automation production lines and is suitable for infrared optics, light-emitting diode (LED) substrates, photoelectric displays, military industry, optical lenses, electronic devices, heat-resistant parts, and other fields. The present disclosure belongs to the technical field of functional materials.

BACKGROUND Sapphire is a crystalline material whose hardness is second only to diamond in the world. Sapphire has high strength and hardness (Mohs hardness: 9), strong resistance to high temperature (melting point up to 2,050°C), abrasion and corrosion, and stable chemical properties, that is, sapphire will not be corroded by acids and can only be eroded at high temperature by hydrofluoric acid (HF), phosphoric acid (H2PO4) and molten potassium hydroxide (KOH). Moreover, sapphire also has a series of characteristics such as high compatibility with semiconductor materials such as gallium nitride, prominent light transmission performance, and excellent electrical insulation performance. Sapphire single crystal is an excellent wave-transparent material, exhibiting high transmittance in ultraviolet (UV), visible light, infrared bands, and microwaves, and can meet the requirements of multi-mode compound guidance (TV, infrared imaging, radar, etc.). Therefore, sapphire is used as a window material and fairing part in the military industry and as an important window material in the field of optoelectronic communication. A large-size single crystal can be grown from a Sapphire material, which has few internal defects, no scattering sources such as grain boundaries and pores, little strength loss, and high wave transmission rate and thus is currently the first choice for wave-transmitting parts. In addition, with electrical insulation, transparency, prominent thermal conductivity, and high hardness, sapphire can be used as a substrate material for integrated circuits and can be widely used in LEDs and microelectronic circuits, which can replace expensive silicon nitride substrates in the manufacture of ultra-high-speed integrated circuits. Sapphire can also be made into optical sensors and other optical communication and optical waveguide devices, such as an observation window for a high-temperature and high-pressure or vacuum container, a heat sink for a liquid crystal display (LCD) projector, a window for a harmful gas detector or a fire monitor, and an optical fiber communication connector box. However, there are still major problems in the downstream processing of sapphire in China. Due to the high hardness and abrasion-resistance of sapphire, a high cost is required for sapphire polishing. In view of the problem of difficult polishing, the present disclosure is mainly intended to provide a novel processing method, namely, sapphire surface vitrification.

SUMMARY The present disclosure is intended to provide a method for greatly improving an optical transmittance of unpolished sapphire by sapphire surface vitrification. In the sapphire surface vitrification method of the present disclosure, the optical transmittance of sapphire can be greatly increased only by preparing glass components in proportion, then incubating at a specified temperature, and slowly cooling in a furnace, which reduces the high cost of traditional mechanical polishing and improve the traditional glass preparation process to a large extent. In the present disclosure, RE20: (RE = Y, La, Gd, and Ce) and SiO: systems are adopted as raw materials required for vitrification, and unpolished sapphire is adopted as a substrate material. A composition formula of glass will be adjusted to achieve the purpose of the present disclosure by process steps of spreading, melting, annealing, inspection, and performance testing of glass raw materials. The vitrification method for enhancing transmittance of unpolished sapphire in the present disclosure is characterized in that Al>Os required in a glass phase is totally provided by the adopted unpolished sapphire substrate material, and in the vitrification, the following glass components are added, in molar percentage: 10% to 30% of RE20: and 70% to 90% of SiOz.

The vitrification method for enhancing transmittance of unpolished sapphire includes the following steps: a) preparation of a glass batch required for the vitrification thoroughly mixing the raw materials based on the contents described above to obtain a glass batch, and uniformly spreading the glass batch on the unpolished sapphire, with a thickness above 1 mm; and b) melting of the glass batch subjecting the sapphire substrate with the glass batch prepared in step a) to thermal treatment in a furnace at 1,400°C to 1,600°C for more than 2 h, naturally cooling the sapphire substrate with the furnace body, and taking the sapphire out from the furnace for test to obtain the sapphire substrate with greatly-improved optical transparency in the present disclosure.

Compared with the existing mechanical polishing, the method for enhancing an optical transmittance of sapphire by subjecting the sapphire to surface vitrification in the present disclosure has the advantages of simple process, low cost and the like. The sapphire with high optical transmittance in the present disclosure can be used in fields of infrared optics, LED substrates, photoelectric displays, military industry, optical lenses, electronic devices, heat-resistant parts, and the like.

The above process requires no clarifying agents such as As20:3 and Sb203, thus resulting in no environmental pollution.

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 shows the transmittance of the samples in Examples 1 to 4 and a one-side- polished sapphire sample, where, the illustration in FIG. 1 shows the pictures of the sapphire substrate samples before and after vitrification.

DETAILED DESCRIPTION The present disclosure is described in further detail below with reference to examples and accompanying draws. The components, process parameters and performance parameters for Examples 1 to 4 of the present disclosure are shown in the following table.

Component Technical | Example 1 | Example 2 | Example 3 | Example 4 TT | Te RE20:; Molar 10% 15% 30% 30% Ve mn S102 Molar 90% 85% 70% 70% ee Sapphire Size R=15mm, | R=15mm, | R=15mm, R=15mm, Total Molar 100% 100% 100% 100% ee Melting 1,400 1,500 1,500 1,600 (°C) Forming Room Room Room Room pen | rn rene or (°C) Transmittance More than | More than | More than More than in UV and 90% 90% 90% 90% visible light The present disclosure adopted the process of slowly cooling in a furnace, and the manufacturing processes for the above examples were basically the same except for the selection system.

In the above examples, melting was conducted in a high-temperature muffle furnace, and cooling forming was also completed in the furnace.

The melting was conducted at 1,400°C to 1,600°C, the temperature was slowly decreased with the furnace, and finally a formed product was taken out.

The inherent quality of the sapphire substrate was observed, and then a sample was collected for transmittance test.

Finally, it is necessary to explain here: The above examples are only used to further describe the technical solutions of the present disclosure in detail and cannot be understood as limiting the protection scope of the present disclosure.

Some non-essential improvements and adjustments made by those skilled in the art based on the above content of the present disclosure shall fall within the protection scope of the present disclosure.

Claims (4)

-5- Conclusions 1. Vitrification method for improving transmittance of sapphire whose surface is unpolished, in which, in the surface vitrification, the following glass components, in mole percentage, are added: 10 % — 30 % to RE2 O3 (RE = Y, La, Gd, and Ce) and 70% - 90% of SiOx. A vitrification method for improving transmissivity of sapphire whose surface is unpolished, wherein, in the surface vitrification, Al:0; required in a glass composition is provided entirely by the sapphire. The vitrification method for improving transmissivity of sapphire whose surface is unpolished according to claim 1 or 2, wherein the vitrification method comprises the following steps: a) preparing a glass charge required for the surface vitrification: thoroughly mixing raw materials required for the surface vitrification based on the contents of claim 1 to obtain a glass charge, and spreading the glass charge evenly on the unpolished sapphire, having a thickness of more than 1 mm; and b) melting the glass charge: subjecting the sapphire with the glass charge prepared in step a) to thermal treatment in a muffle furnace at a high temperature of 1400 °C — 1600 °C for more than 2 hours, cooling naturally of the sapphire with the furnace body and taking the sapphire out of the furnace for testing to obtain the sapphire having significantly improved transmissivity as in the present disclosure. A vitrification method according to claim 3, wherein, traditionally, sapphire has to be mechanically polished to obtain high optical transmittance, but the present disclosure provides sapphire with high optical transmittance by subjecting sapphire to surface vitrification through a chemical reaction.