Switchable molecular ferroelectric compound

2014 Fiscal Year Final Research Report

• Project/Area Number: 25620046
• Research Category: Grant-in-Aid for Challenging Exploratory Research
• Allocation Type: Multi-year Fund
• Research Field: Inorganic chemistry
• Research Institution: Kyushu University
• Principal Investigator: SATO Osamu 九州大学, 先導物質化学研究所, 教授 (80270693)
• Project Period (FY): 2013-04-01 – 2015-03-31
• Keywords: 誘電特性

Outline of Final Research Achievements

A pure organic single crystal [H2dabco][2CB]2 ([H2dabco]2+ = diprotonated 1,4-diazabicyclo[2.2.2]octane, 2CB- = 2-chlorobenzoate), which exhibits ferroelectricity above room temperature, was synthesized. The crystal is constructed from trimer units in which two 2CBanions are bridged by one diprotonated [H2dabco]2+ cation. The [H2dabco]2+ cation undergoes an order-disorder phase transition above room temperature. In the high temperature phase, the [H2dabco]2+ cation located at the middle position of the trimer is rotated with disorder about its N--N axis and lies at the center of inversion. When the temperature drops below the phase transition temperature, the [H2dabco]2+ cation is frozen such that it is ordered and deviates from the center of the trimer unit. This displacement of the cation leads to symmetry breaking (nonpolar space group Pbca to polar space group Pna21) and generates a spontaneous polarization along the crystallographic c axis.

Free Research Field

物質化学