Conductivity of Materials

The question asks us to identify the compound with the highest conductivity among Si₃N₄, α-BN, AlN, and (SN)_x. To answer this, we need to consider the electrical conductivity properties of each substance.

Analyzing Conductivity Properties

• Si₃N₄ (Silicon Nitride): Silicon nitride is a ceramic material widely known for its excellent mechanical and thermal properties. It is also a very good electrical insulator. Insulators have very low electrical conductivity because their electrons are tightly bound and cannot easily move to carry current.
• α-BN (α-Boron Nitride): α-Boron nitride (hexagonal boron nitride) is structurally similar to graphite but is chemically inert and electrically insulating. Like silicon nitride, it has a large bandgap, making it an excellent electrical insulator.
• AlN (Aluminium Nitride): Aluminium nitride is another ceramic material. While it is known for its high thermal conductivity, it is a wide bandgap semiconductor and acts as an excellent electrical insulator at room temperature. Its electrical conductivity is very low compared to conductors.
• (SN)_x (Poly(sulfur nitride) or Polythiazyl): This is a unique inorganic polymer. Unlike most polymers which are electrical insulators, (SN)_x exhibits metallic conductivity. It is conductive along the polymer chains and is even superconducting at very low temperatures (below 0.3 K). Its conductivity is comparable to that of some metals.

Comparing the four compounds:

Si₃N₄, α-BN, and AlN are all electrical insulators or semiconductors with very low conductivity. (SN)_x, on the other hand, is a metallic conductor.

Therefore, the compound with the highest conductivity among the given options is (SN)_x.