Protonic and Oxygen Quasichemistry in Solid Oxides
Dear Colleagues!
Please consider and discuss below presented сomplete quasichemical description of some cubic oxides similar YO1.5 and double perovskites in water and oxygen atmosphere
Y2O3 doped by CaO
under water vapor and oxygen:
y2{(1+ξ)2 - 4v3} - 3y*(1+ξ) + x*(3-x) = 0
y=[OHO·], v3 =1/w3 , ω 3=K3Pwater , ω 4=K4 ( Poxygen)1/2
ξ = (ω4 / ω3)1/2 , x = [Ca], [OO·] = [h] = yξ
Y2O3[Vi] with structural vacancy
under water vapor and oxygen:
y3 4α (v7 + α2) -16 (y*α)2 +21 (y*α) – 9 = 0
y=[OHO·], v7 =1/ω7 , ω7 = K7Pwater, ω 9 = K9 ( Poxygen)1/2
ξ 9,7 = (ω9 / ω7)1/2 , α = (1 + ξ 9,7)
[Oi//] = 0,5*y*α, [OO·] = [h] = y*ξ 9,7
The double perovskites are protonic conductors with structural disordering of oxygen subsystem As the example is considered Sr6-2xTa2+2xO(11+3x)[Vx](1-3x).
K1Pwater = [OHo·]*[OHV/] /[OOx]*[Vx] = ω1 -- described the equilibrium with water vapor resulted in fulfilling of structural vacancy by oxygen ion from water molecule and the formation of two hydroxide ions with different effective charge ion “host” oxygen and on “guest” oxygen in structural vacancy corresponding.
K2Pwater = [OHo·]2*[OV//] /[OOx]2*[Vx] = ω2– described the equilibrium with water vapor resulted in fulfilling of structural vacancy by oxygen ion from water molecule and the formation of two equal hydroxide ions on “host” oxygen, “guest” oxygen forms the oxide ionin structural vacancy corresponding.
K2 ( Poxygen)1/2 = [OO·]2*[OV//] /[OOx]2*[Vx] = ω3– described the equilibrium with molecular oxygen fullfilled the structural vacancy/.
[OHo·] = yo; [OHV/] = yV,
ῶ1 = 1/ω1 , α = 1 + (ω2 /ω3)1/2
I have decided to show the pair of equations linked up yO and yV. The final equation for the dependence of hydrogen content on factor of nonstoichiometry X and corresponding constant sof equilibrium of perovskite with gaseous phases could be obtaind. However, according our experience, using this pair is moe effective at the analysis of real situation . The matter is that the formation of hydroxide ions with contrary effective charge is very interesting effect from fundamental point of view.
yV = {(A – αyo)(2B – αyo)/[( A – αyo) + 2ῶ1 yo]
yV = {[αyo – X(2B - αyo)]/(1-X)}
where X = ω2[(A- αyo)/ yo], А=11+3х, В=1-3х
sub
sub/strongO strong