This thread is summarising previous material, with corrections. PLEASE check these calculations! the answer now is in line with Y_Po's estimates a long time ago.
The argument is that there is no way that BaTiO3 can sustain enough polarisation to have eestor claimed ED at 350V/um.
This means that the measured low voltage permittivity must saturate before 350V/um (always assuming vthe dielectric does not break down.
Background. Everyone else measures saturation for paraelectric BaTiO3 MUCH smaller than required for eestor ED. It is published in various papers. But we can ignore this - eestor might have found some way round it.
Fundamentally, BaTiO3 can only achieve high polarization through movement of Ti ions in lattice. The effect of this is easily calculable:
Assume:
qe=Electron charge = 1.6E-19 (SI units)
lattice is 4A =0.4nm = 4E-8cm
Ti ion dynamic charge is +7.5qe.
We get volumetric Ti ion density from
Avogadro's constant * density BatiO3 / molecular no baTiO3 =
6*10E23*6/233 = 1.5*10E22 Ti ions/cc
To verify this we expect one Ti ion per (0.4nm)^3 =
1/(4E-8)^3/cc = 10E24/64= 1.5E22 Ti ions/cc
The max dipole moment per Ti we calculate as:
qe*7.5*0.4*E-9*theta. (SI units) where theta is the fraction of the lattice the Ti ion moves. If the Ti ion moves towards one corner of the lattice cell we have theta=1.5 for translational symmetry. Let us therefore assume theta=0.75 for max dipole moment. Still too large, but it will do. This is equivalent to 3A movement.
qe=1.6*E-19.
So:
P0 = 1.6E-19*0.75*7.5*4E-10 =9E-29 (SI units)
The polarization density P is:
P = 9E-29*1.5E22 (in units of polarization/cc where polarization is SI)
= 1.4E-6
So at 350V/u we have ED (/cc) is
ED = (1/2)E.P = 0.5*3.5E8*1.4E-6= 250J/cc
This is looking more plausible than the previous max value, and comes in a comfortable 1/10 of eestor claimed ED. I think it is compatible with Y_Po's calculation from a long time ago? To get eestor ED you need 75 electrons to move 3/4 of the lattice.
Perhaps somone could check these calculations!
The "assumptions" -
dynamic charge on Ti = +7.5e
lattice constant = 4A
distance moved = 1/2 of lattice (diagonally). Diagonal is 6A, so max movement is 3A
Bottom Line: Max Energy Density is 250J/cc
On other threads we have shown that the max energy density due to Al2O3 etc is also low.
Assumptions: 1) E=1/2CV2
(Only dummies assume this)
