Organic ferroelectricshydrogen bond base
What is ferroelectricity?
• Ferroelectricity is a property of certain materials that have
a spontaneous electric polarization that can be reversed by the
application of an external electric field.
Why organic ferroelectrics?
Flexible, sustainability, easy to get.
How do find organic ferroelectrics?
1.
First, molecules should have dipoles
• For molecules there are three types of dipoles:
• Permanent dipoles: These occur when two atoms in a molecule have
substantially different electronegativity: One atom attracts electrons
more than another, becoming more negative, while the other atom
becomes more positive. A molecule with a permanent dipole moment is
called a polar molecule.
• Instantaneous dipoles: These occur due to chance
when electrons happen to be more concentrated in one place than
another in a molecule, creating a temporary dipole.
• Induced dipoles: These can occur when one molecule with a permanent
dipole repels another molecule's electrons, inducing a dipole moment
in that molecule. A molecule is polarized when it carries an induced
dipole.
2. Second, crystal structure should be pseudosymmetry,
or displacive
Two types of organic ferroelectrics
1. O-H elongates, while hydrogen bonds become
shorter and stronger
The spontaneous polarization of Phz-H2xa along the b axis arises
from a change in crystal symmetry from space group P21/n to the
uniaxially polar space group P21.
2. O-H…N  O…H-N, protons transfer
Our goal
• 1. CCA is proton transfer Organic ferroelectrics.
• 2. explore different kinds of organic ferroelectrics.
• 3. look for layer by layer crystal structure for thin films.
• 4. co-crystalization for more kinds of organic ferroelectrics.
• 5. more ways to search organic ferroelectrics.