Metals:
* Nickel: Used in thermistors, temperature sensors, and resistance thermometers.
* Copper: Widely used in electrical wiring and applications where predictable resistance changes are needed.
* Platinum: Used in high-precision resistance thermometers due to its stable and linear temperature response.
* Iron: Used in some heating elements and magnetic applications.
* Tungsten: Used in incandescent light bulb filaments due to its high melting point and resistance to oxidation.
Semiconductors:
* Silicon: Used in a wide range of electronic devices, including transistors, diodes, and integrated circuits.
* Germanium: Similar to silicon, but with a lower melting point and slightly different properties.
* Carbon: Used in resistors, thermistors, and certain types of sensors.
* Metal Oxides: Many metal oxides, particularly those of transition metals, exhibit PTC behavior. Examples include:
* Nickel Oxide (NiO): Used in PTC thermistors and sensors.
* Copper Oxide (CuO): Used in various applications including gas sensors.
* Titanium Dioxide (TiO2): Used in PTC thermistors, gas sensors, and photocatalysts.
Other Materials:
* Ceramics: Certain ceramic materials, like barium titanate (BaTiO3), exhibit a strong PTC effect and are used in thermistors and sensors.
* Polymers: Some polymers, like polyethylene and polystyrene, show a positive temperature coefficient of resistivity.
Important Considerations:
* PTC behavior can vary significantly: The magnitude and temperature range of the PTC effect depend on the specific material and its composition.
* Non-linearity: The resistance change with temperature can be non-linear for some materials.
* Temperature Limits: All materials have a maximum operating temperature beyond which they may degrade or change their properties.
Applications:
PTC materials are used in a wide range of applications, including:
* Temperature Sensing and Control: Thermistors, temperature sensors, and control systems.
* Overcurrent Protection: PTC devices can act as self-resetting fuses to protect circuits from overheating.
* Heating Elements: PTC heaters offer advantages like fast heating and precise temperature control.
* Gas Sensing: Certain PTC materials can detect specific gases based on their interaction with the material's resistance.
* Electronics: PTC materials play a role in various electronic devices, such as power supplies, motors, and power electronics.
Remember that this list is not exhaustive, and there are many other materials that exhibit PTC behavior. The specific material selection for a particular application depends on its desired properties, operating conditions, and cost considerations.
