Multi-section spiral filaments are a common filament structure used in lighting devices.
Different filament materials exhibit noticeable variations in luminous efficiency, color temperature, lifespan, stability, and cost.
The following sections provide a detailed comparison across these aspects.
- Luminous Efficiency
Tungsten:
Tungsten is one of the most widely used materials for multi-section spiral filaments.
It has a high melting point, low evaporation rate, and excellent thermal stability at elevated temperatures.
Its luminous efficiency is relatively high — in traditional incandescent lamps, tungsten spiral filaments can convert about 10–20% of electrical energy into visible light.
This is because tungsten can reach very high operating temperatures when heated, producing bright illumination.
Molybdenum:
Molybdenum also features a high melting point and good electrical and thermal conductivity.
However, the luminous efficiency of molybdenum spiral filaments is slightly lower, typically around 8–15%, due to its comparatively weaker electron emission capability.
Under the same electrical conditions, fewer photons are generated.
Carbon Fiber:
As a new filament material, carbon fiber offers high specific strength and modulus as well as good conductivity.
Its luminous efficiency can reach 15–25%, thanks to its unique microstructure, which enhances energy conversion efficiency and reduces heat loss.
- Color Temperature
Tungsten:
Tungsten multi-section spiral filaments usually emit light with a color temperature of 2700–3000 K, producing a warm white glow.
This comfortable, cozy tone makes tungsten lamps ideal for home, hotel, and decorative lighting applications.
Molybdenum:
Molybdenum filaments have slightly lower color temperatures, typically 2500–2800 K, yielding a warmer, yellowish tone.
Such light is suitable for settings like museums or galleries, where it enhances the texture and color of artworks or exhibits.
Carbon Fiber:
The color temperature of carbon-fiber spiral filaments varies with composition and doping but generally ranges between 3000–4000 K, producing a neutral white light.
This spectrum offers high color rendering and is well-suited for environments requiring accurate color perception, such as retail stores and offices.
- Lifespan
Tungsten:
Under normal operation, tungsten spiral filaments last about 1000–2000 hours.
Over time, tungsten gradually evaporates and thins, eventually leading to filament breakage.
Filling the bulb with inert gases such as argon or nitrogen can slow evaporation and extend service life.
Molybdenum:
Molybdenum filaments have a somewhat shorter lifespan — typically 800–1500 hours — due to weaker oxidation resistance at high temperatures.
To enhance durability, special anti-oxidation treatments or protective coatings are often applied during manufacturing.
Carbon Fiber:
Carbon-fiber spiral filaments can last 2000–3000 hours on average.
They offer excellent chemical stability and resist oxidation at high temperatures.
Their high mechanical strength also allows them to handle greater current and heat without degradation.
- Stability
Tungsten:
Tungsten filaments must endure high temperatures and currents, which can lead to sagging or deformation.
To improve stability, manufacturers often introduce additives (such as potassium or sodium) to enhance mechanical and thermal strength.
Proper filament structure and support design also contribute to improved stability.
Molybdenum:
Molybdenum filaments are less stable and more sensitive to vibration or impact due to their lower ductility compared with tungsten.
To avoid breakage, external mechanical shocks should be minimized during installation and use.
Carbon Fiber:
Carbon-fiber filaments provide excellent stability under varying conditions.
They have a low thermal expansion coefficient and high resistance to vibration and impact, maintaining reliable performance in complex working environments.
- Cost
Tungsten:
Tungsten is relatively abundant and its processing technology is mature, resulting in a stable and cost-effective supply.
Therefore, tungsten multi-section spiral filaments are widely used in various lighting applications with high cost-performance value.
Molybdenum:
Molybdenum is more expensive and requires specialized equipment and techniques for processing, leading to higher production costs.
Thus, molybdenum filaments are generally used in applications demanding superior performance or specific characteristics.
Carbon Fiber:
Carbon fiber production is technologically complex and costly.
Although its performance is excellent, its high cost currently limits widespread use.
However, with advances in carbon-fiber manufacturing and declining costs, carbon-fiber filaments are expected to become more prevalent in the future.
Conclusion
Multi-section spiral filaments made from different materials vary significantly in luminous efficiency, color temperature, lifespan, stability, and cost.
In practical applications, the optimal choice should be based on the specific lighting scenario and performance requirements, balancing illumination quality and economic efficiency to achieve the best results.