Chemistry: Solid State: Applications of N-Type and P-Type Semiconductors (For CBSE, ICSE, IAS, NET, NRA 2022)

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Applications of N-Type and P-Type Semiconductors

Due to tier special properties, n-and p-type semiconductors are used in several applications.

  • Diodes: Diode is a combination of n-type and a p-type semiconductor. Diodes are used as rectifier to convert an AC signal to a DC signal.
  • Transistors. Transistors are made by combination of 3 layers of semiconductors. Transistor of n-p-n type is made by sandwiching a layer of p-type semiconductor between two layers of n-type semiconductors and of p-n-p type by sandwiching a layer of n-type semiconductors between two layers of p-type semiconductor. Transistors are used as detectors and amplifiers of radio or audio frequency signals. They are used in circuits of solid-state devices.
  • Solar cells: Solar cells are photo diodes which emit electrons when sunlight falls on them. They are used to convert solar energy into electricity.

Magnetic Properties

  • All substances are affected either attracted or repelled by a magnetic field.
  • The magnetic properties present in any substance are due to the electrons present in it.
  • Electrons are negatively charged particles.
  • When an electron revolves around nucleus and spins about its own axis, two types of magnetic moments are created – orbital magnetic moment due to its revolution around the nucleus and spin magnetic moment due to its spin.
  • The magnetic properties of a substance depend upon the orientation of these tiny magnets.

On the basis of magnetic properties, all substances can be classified into five categories:

  • Paramagnetic
  • Diamagnetic
  • Ferromagnetic
  • Anti-ferromagnetic
  • Ferrimagnetic

Paramagnetic Substances

  • These substances are weakly attracted in a magnetic field.
  • O2, Cu2 + , Fe3 + and Cr3 + are some examples of paramagnetic substances.
  • Para magnetism is due to the presence of one or more unpaired electrons in an atom, molecule or ion.

Diamagnetic Substances

  • When placed in a magnetic field, the diamagnetic substances are weakly repelled by it.
  • H2O, NaCl and C6H6 are some examples of such substances.
  • Diamagnetism is shown by substances in which all the electrons are paired.

Ferromagnetic Substances

  • When placed in a magnetic field, ferromagnetic substances are strongly attracted by it.
  • Fe, Ni, Co, Gd, MnAs, CrBr3 and CrO2 are such substances.
  • These substances can be permanently magnetized.
  • In solid state, the metal ions of ferromagnetic substances are grouped together into small regions called domains.
  • In each domain, the individual magnetic moments of the metal ions are directed in the same direction, as a result, each domain acts as a tiny magnet.
  • These domains are randomly oriented which cancels out their magnetic moment.
  • When placed in a magnetic field, all the domains get oriented in the direction of the magnetic field which increases their magnetic moments and makes them strong magnets.
  • They lose their ferromagnetism by mechanical disturbance or on heating above a certain temperature, called Curie temperature they become paramagnetic.

Antiferromagnetic Substances

  • Some substance have domains like ferromagnetic substances, but their domains are oppositely oriented and cancel out the magnetic moments of each other they are called as anti-ferro magnetic substances.
  • FeO, MnCl2, MnO, Mn2O3 and MnO2 are examples of anti-ferromagnetic substances.
  • They become paramagnetic on heating above a certain temperature.

Ferrimagnetic Substances

  • Some substances like Fe3O4 (magnetite) and ferrites (MFe2O4 where M is a bivalent cation like Cu2 + , Zn2 + ) show an intermediate behavior between that of ferromagnetic and antiferromagnetic substances.
  • These substances are strongly attracted by magnetic field as compared to paramagnetic substances but weakly as compared to ferromagnetic substances.
  • Their domains are aligned in parallel and anti-parallel directions in unequal numbers.
  • They also become paramagnetic on heating above a certain temperature.
Ferrimagnetic Substances

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