Re: what is the real meaning of crystaline net imperfections

Richard,
I am not certain what you are calling a crystaline net.  Material science 
people often refer to a crystalline lattice.  Most metals consist of 
multiple crystals which together form a crystalline lattice.  The area 
between the crystals often contains impurities like sulphur or phosphorus.

Metals can be grown as very large single crystals.  The single crystal 
still has electrical resistance at ambient (room) temperatures.  The 
impurities at the grain boundaries will contribute to increased resistance 
compared to a single crystal.  

Only when a conductor is cooled below it's superconducting transition 
temperature does the electrical resistance become zero.

Bob Novak
Specialist - Process R&D
Carpenter Technology