Tag: chemistry

The temperature at which a substance starts behaving as super-conductor is called transition temperature. For most metals, the transition temperature lies between 2 and 5 K.

Superconductors are diamagnetic.

The highest temperature at which superconductivity has been observed is 23 K for alloys of niobium $(Nb _3Ge)$.

The n-type semiconductor can be produced  by doping impurity atoms of valence 5 i.e, pentavalent atoms like phosphorous and so electrons are majority charge carriers and Holes are minority charge carriers.

$Tl _2Ca _2Ba _2Cu _3O _{10}$ possess superconductivity at 125 K.

Superconductors have applications in electronics, building magnets, aviation, transportation (trains which move in air without rails) and power transmission.

The n-type semiconductors are obtained when $Si$ or $Ge$ are doped with elements of group 15, eg, Arsenic $(As)$, while p-type semiconductors are obtained when $Si$ or $Ge$ are doped with traces of group 13 , ie Indium $(In)$ , Boron $(B)$.

An extrinsic semiconductor is one that has been doped; during manufacture of the semiconductor crystal a trace element or chemical called a doping agent has been incorporated chemically into the crystal, for the purpose of giving it different electrical properties than the pure semiconductor crystal.

$p-$type semiconductors have a larger hole concentration than electron concentration. In p-type semiconductors, holes are the majority carriers and electrons are the minority carriers. $p-$type semiconductors are created by doping an intrinsic semiconductor with acceptor impurities. A common $p-$type dopant for silicon is boron or gallium. There will be no charge on the semiconductor.

$TiO _{ 3 }$ behaves as conductor or insulator depending on temperature because of variation of energy gap between valence band and conduction band with the variation of temperature.