Question

In: Chemistry

(a) Derive a relation for the oxygen pressure dependence of electrical conductivity in NiO.       (b)...

(a) Derive a relation for the oxygen pressure dependence of electrical conductivity in NiO.

      (b) Discuss the effects of Cr2O3 additions on the electrical conductivity of NiO, giving equations describing the temperature at which the conductivity changes from intrinsic to extrinsic in relation to the impurity concentration.  

Solutions

Expert Solution

A)-In the various oxygen pressures, we investigated the temperature dependency of the electrical conductivity (σ) of NiO. It changes from the form A exp (-E/kT) to A' exp (-E/2kT) with the increase of oxygen pressure (P:10-3~760 mmHg). From this change we can determine the unique value of the activation evergy E. E=1.25 eV. The dependency upon the oxygen pressure at a definite temperature can be expressed generally,by the formula, σ ∞ Px1. If we assume, as usual, that when the oxygen pressure increases,the nickel ions moves towards the surface to react with oxygen and extend the lattice of NiO, leaving vacant lattice points on the nickel lattice of NiO, and that such vacant lattice points form the impurity levels, then we can obtain the relation σ ∞ P41. Experimental value of x is 3.7 at 1000°,almost in accord with the above-mentioed result. But at lower temperatures we gain the smaller value of x,until finally it reaches to the relation σ ∞ P. And with such assumption,we cannot explain the change of the temperature dependence of the conductivity in the different oxygen pressures.
So,we assume that the nickel ions which left the normal lattice points,partially extend the lattice NiO at the surface,and partially occupies the interstitial positions. Then, thenumber of the vacant lattice points (Nh) is proportional to √P,and the number of the interstitial nickel ions (Nf) is inversely proportional to√P.
So the number of electrons at the imprurity levels,and of positive holes in the full band varies depending upon the oxygen pressure. Using these relations,we can derive the theory which may account for the experimental data.
From our data,we get a constant δ=Nf/h ~ 2 × 10-3 at 1000°, P=760 mmHg, in which n denotes the number of free positive holes. This value of δ is very small, nevertheless the effect of this small value is very serious

B)-The electrical conductivity of single crystals of α-Al2O3 doped with Cr2O3 (0.03–2.5 wt%), NiO (0.75 wt%) plus Cr2O3 (0.03–0.15 wt%), and NiO (0.75 wt%) has been measured under 1 MeV electron irradiation at 300 K to investigate the effects of the concentration of impurity and of the depth of impurity levels in forbidden bands on the radiation induced conductivity (RIC). The RIC of Cr2O3 and/or NiO doped α-Al2O3 decreases with increasing concentration of Cr2O3 and/or NiO dopants. The electrical conductivity of 2.5 wt% Cr2O3doped α-Al2O3 is smaller than any other doped materials tested. The dose rate exponent for Cr2O3 doped α-Al2O3 is smaller than that for NiO plus Cr2O3 doped material, due to deeper trapping centers of Cr (5.8 eV from the conduction band) than those of Ni (2.0 eV). Doping impurities with deep trapping centers are most effective for suppressing RIC.


Related Solutions

4 (a) Derive a relation for the oxygen pressure dependence of electrical conductivity in NiO. (b)...
4 (a) Derive a relation for the oxygen pressure dependence of electrical conductivity in NiO. (b) Discuss the effects of Cr2O3 additions on the electrical conductivity of NiO, giving equations describing the temperature at which the conductivity changes from intrinsic to extrinsic in relation to the impurity concentration.
4 (a) Derive a relation for the oxygen pressure dependence of electrical conductivity in NiO.      ...
4 (a) Derive a relation for the oxygen pressure dependence of electrical conductivity in NiO.       (b) Discuss the effects of Cr2O3 additions on the electrical conductivity of NiO, giving equations describing the temperature at which the conductivity changes from intrinsic to extrinsic in relation to the impurity concentration.  
Thermodynamic question Derive relation between saturated vapor pressure and temperature. and apply the relation to the...
Thermodynamic question Derive relation between saturated vapor pressure and temperature. and apply the relation to the case of water.
Electrical Conductivity Determination for Intrinsic Silicon at 150°C Cakulate the electrical conductivity of intrinsic silicon at...
Electrical Conductivity Determination for Intrinsic Silicon at 150°C Cakulate the electrical conductivity of intrinsic silicon at 50 degrees * C C.100 100^ C 200^ C and plot the conductivity that you have found versus temperature 300 degrees * C
The electrical conductivity of a 1 M HCN solution is much less than the conductivity of...
The electrical conductivity of a 1 M HCN solution is much less than the conductivity of a 1 M HCl solution because: -HCl is a weak electrolyte, HCN is a strong electrolyte. -HCl is a strong electrolyte, HCN is a weak electrolyte. -HCN contains more atoms than HCl so it has greater mass. -HCl has a greater mass than HCN. -The charge on the chloride ion is higher than the charge on the cyanide ion.
Derive an expression for the time dependence of the free radical concentration
Derive an expression for the time dependence of the free radical concentration
Derive the AS relation and draw the AS curve. Explain the properties of AS relation
Derive the AS relation and draw the AS curve. Explain the properties of AS relation
Derive the AS relation and draw the AS curve. Explain the properties of AS relation
Derive the AS relation and draw the AS curve. Explain the properties of AS relation
Derive the AS relation and draw the AS curve. Explain the properties of AS relation.
Derive the AS relation and draw the AS curve. Explain the properties of AS relation.
(a) Derive a Maxwell relation from the exact differential da = edx + gdy. (b) A...
(a) Derive a Maxwell relation from the exact differential da = edx + gdy. (b) A gas container is separated by a partition and the volume of the left side is half of the volume as of the right side. The left column is filled with a 1 mole of helium gas and 2 moles of argon can be found in the right column. Consider that the system is thermally isolated, calculate the change in entropy using appropriate Maxwell relation...
ADVERTISEMENT
ADVERTISEMENT
ADVERTISEMENT