### 2.3.3 Resistors and Heating

Resistors

| Basic requirements for resistors (still one of the most numerous component in circuits) are:
|  | Large region of R values (= device resistance in W) within one production technology. Small (ideally vanishing) temperature coefficient . Minimal noise. Small dependence of r on production parameters (good repeatability). No Ageing. Small thermoelectrical coefficients to Cu (you want a resistor, not a thermoelement).
| Materials of choice include
|  | Ta, Ta based alloys, and in particular "Constantan" (55% Cu, 44% Ni, 1% Mn), a resistor material with an especially small temperature coefficient ar, but a large thermoelectric coefficient).
|  | Strange mixtures of conductors and insulators including "Cermet" (short for Ceramics - Metals), e.g. Cr - SiO2.
| Details and data in the (future) link.

Heating

| Basic requirements for heating elements are:
|  | High melting point. Chemical stability at high temperatures and in potentially corrosive environments. Mechanical strength at high temperatures.
| The choice of a materials depends significantly on the range of temperatures envisioned. We have:
|  | FeNiCr, FeNiAl alloys.
|  | Pt, W, Ta, Mo - stable elements with a high melting point.
|  | MoSi2 Among more industrial applications also used as heaters in dish washers - this is very aggressive environment!
|  | Graphite (up to 3000 K in non-oxidizing gas).
| Some details and data can be found in the links.
|  | Overview of resistivity and temperature range for some materials
|  | Maximum temperatures for some materials

© H. Föll (Advanced Materials B, part 1 - script)