#### 1. Introduction

Impedance spectroscopy studies show that the K
*
*MnO

The A- and B-site doping of La
*x *= 0–0.4 in La
*
*NiO

*NiO*x

As shown for La
*
*Ni

*O*y

*x*= 0.5,

*y*= 0.4 [10] improving its performance as a cathode material for SOFCs [11]. Taking into account the recent results reported in [12], where an increase in strontium content from

*x*= 0.2 to

*x*= 0.8 in La

*NiO*x

*O*y

*y*= 0.1, 0.3, and 0.4) oxides [10].

#### 2. Methods

The La
*K*

The preparation of cell for oxygen permeation studies and the experimental details were described in [10]. The data were collected at 800, 850, 900, 950, and 1000
*p*
*p*

#### 3. Results

The steady-state oxygen permeation fluxes (*j*) through the dense La
*p*
*J*) that was calculated as follows:

(1)
where *d* is a membrane thickness.

According to Eq. (1) the specific oxygen permeability, which is proportional to the *j
* product, will not depend on membrane thickness, if the oxygen permeation flux through a dense membrane is limited by bulk oxygen diffusion. As can be seen from Figure 1(b), the obtained

*J*values were independent of the membrane thickness within the experimental error at 800, 850, and 900

In order to assess the role of bulk diffusion and surface exchange in the oxygen permeation flux, the critical membrane thickness (*d*
*d*
*p*

(2)
where *p*
*p*
*p*

The critical membrane thickness, ambipolar conductivity, and the sum
*p*
*d*
*f*(log(0.21/*p*
*d*
*T *

The calculated values of ambipolar conductivity and the sum of reverse exchange constants
*p*
*p*
*p*
*
*Ni

*O*y

The reciprocal temperature dependencies of oxygen-ion conductivity (σ
*D*) for La
*
*O

*O*y

*D*in oxygen-deficient La

*O*y

The surface oxygen exchange coefficients in air can be estimated if one assumes that at low *p*
*k
* value can be easily found from the corresponding sum

*j*=

*f*(ln(

*p*

*p*

*p*

*p*

*p*

*k*

*O*y

*O*y

#### 4. Conclusion

The studies of oxygen permeation flux through dense La
*
*O

*x*= 0.5 to 0.8 reduced the activation energy of surface exchange almost twice leading to a similar surface exchange kinetics in La