What Are Transparent Ceramics
Alumina, zirconia, aluminum nitride, and other inorganic material powders can be formed into a blank with a specific shape to create transparent polycrystalline ceramics. Then it is sintered in a hydrogen atmosphere furnace or under other special circumstances to create ceramics with a specific transparency. In addition to the inherent high insulation, high temperature resistance, and corrosion resistance of ceramics, transparent ceramics also have optical properties that are comparable to those of single-crystal sapphire, and also have good thermal shock resistance and mechanical properties. Transparent ceramics are an excellent matrix material used in laser, lighting, optics, and other industries. They are frequently used to manufacture high-voltage halogen lamp tubes, laser ceramics, wave-transparent and window materials, inorganic scintillators, and light radiation goggles, etc.
Advantages and Disadvantages of LED Lighting
Electronic technology is advancing incredibly quickly nowadays, and semiconductor lighting is becoming more and more popular. After incandescent, fluorescent, and high-voltage halogen lighting, LED lighting is regarded as the fourth generation of lighting sources.
The benefits of LED lighting over conventional light sources include the following aspects:
(1) A long service life of up to 100,000 hours under the good heat dissipation circumstance;
(2)High luminous efficiency, because LEDs are made of semiconductor materials, the energy released is primarily concentrated in the visible light region, the spectrum is narrow, and its luminous efficiency can range from 50 to 200lm/W.
(3) Eco-friendly and green, it doesn't contain hazardous materials like mercury and lead, and its recycling waste won't pollute the environment.
LEDs, however, also experience some issues. The primary cause is that LEDs are cold light sources that generate light through electronic transitions between different energy bands. The spectrum lacks infrared components and is therefore unable to radiate heat. The service life will be shortened and the high power of LEDs will be directly hampered by difficult heat dissipation. Another issue is that energy is not fully utilized because conventional LED lamps can only emit light from one side due to material limitations. The burden of heat dissipation is increased at the same time because a significant amount of light energy that cannot be emitted from the back side is gathered on the substrate and transformed into heat energy.
Application of Transparent Alumina Ceramics in LED
To generate the effect of multi-sided lighting, as illustrated in the image below, one enhancement measure for LED multi-angle lighting on the market involves creating a bulb structure, connecting numerous LED chips in series, or installing the chips at various angles.
(a picture)
Since chips rather than filaments are what produce the light in LED lamps, a carrier must be used. To meet the demands of multi-angle lighting, the substrate must be transparent. As a result, in addition to its use as a supporting substrate and a heat dissipation medium, the chip packaging substrate that with a certain light transmittance has gained increasing attention in order to satisfy the requirements for uniform and effective light emission as the LED lighting industry has grown. This suggests the following specifications for the substrate used for LED packaging:
(1)It has a certain strength and can carry chips;
(2) It has a specific light transmittance that enables the LED lamp to emit light in all directions;
(3)It has high thermal conductivity, capable of dissipating heat, which facilitates the wick's heat dissipation;
(4) It can be produced in large quantities and at a low cost.
Currently, the most common substrate materials are sapphire and glass, but glass substrates have poor heat dissipation performance, which will shorten the service life of lamps. Although sapphire is effective at dissipating heat, it is a single crystal of alumina. The conditions under which single crystal materials are prepared are harsh; as a result, the yield is low, and the cost of production is excessive. Contrarily, polycrystalline transparent alumina ceramics are less expensive to manufacture than sapphire and have higher strength and thermal conductivity than glass materials. As a result, in the LED field, where strength, thermal conductivity, light transmittance, and production cost must be taken into consideration comprehensively, alumina transparent ceramics are the most promising sapphire substitutes, capable of meeting the performance requirements of emitting lights from all directions for LED packaging substrates.
Conclusion
Transparent alumina ceramic substrates are anticipated to replace sapphire substrates in the field of LED lighting thanks to the advancement in its mass production technology. The production of transparent alumina ceramics with high light transmittance and high thermal conductivity currently faces some bottlenecks. To gradually catch up with foreign products and raise product quality, it is necessary to start with powder treatment, molding, and microstructure control.