I have read that in non-metals solids the electric resistivity is reduced if we increase temperature.But this isn't logical.I mean if temperature is increased ok the electrons get extra energy but as well the vibration of the atoms is increased so electric resistivy is increased.Temperatures cant make electrons overcome the band gap easily.There should be an increase till the temperature is high enough so with little energy the valence electrons would get ionized and then electric resistivity to be dicreased. Where am I wrong?Help appreciated

  • $\begingroup$ You are right. But till the temperature is that high, there should be an increase, and so it is. $\endgroup$ – Ivan Neretin Mar 1 '19 at 18:22
  • $\begingroup$ Yeah but why tables show a negative temperature coefficient of resistivity for some materials then? $\endgroup$ – Max Destiny Mar 1 '19 at 20:07
  • $\begingroup$ Well, just like that: as T grows, more electrons make it across the band gap, hence more charge carriers, hence more conductivity, even though the situation for each particular electron grows worse. $\endgroup$ – Ivan Neretin Mar 1 '19 at 20:09
  • $\begingroup$ What you write doesnt make any sense . 1 hour ago you said that the resistivity is increased $\endgroup$ – Max Destiny Mar 1 '19 at 20:11
  • $\begingroup$ Then I might have misunderstood your original post, sorry about that. No, it is the conductivity that increases, and I just explained why. $\endgroup$ – Ivan Neretin Mar 1 '19 at 20:31

Between 273 K and 500 K the intrinsic carrier concentration in Si increases by about 5 orders of magnitude. Compare with the decrease in conductivity of a metal over that range. Increase in carriers far outweighs the increased scattering of carriers.

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