Structural and Thermal Properties of All-Organic Dielectric Material MDABCO(NH4)(NO3)3

Nakao, Takato A.

doi:10.1021/acs.jpcc.6c01768

Structural and Thermal Properties of All-Organic Dielectric Material MDABCO(NH4)(NO3)3

2026-04-01

0

PRE

AI

N

Nakao, Takato A.

M

Muroga, Mika

M

Moriyama, Takuma

K

Kobayashi, Takuto

S

Shintaro Ueno

K

Kuwabara, Tetsuo

I

Ichiro Fujii

W

Wada, Satoshi

M

Maiko Kofu

H

Hiroshi Akiba

O

Osamu Yamamuro

Y

Yoshihiko Okamoto

J

Jun‐ichi Yamaura *

DOI：10.1021/acs.jpcc.6c01768

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Abstract

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Organic ferroelectrics are attracting attention as flexible, lightweight, and environmentally benign alternatives to inorganic perovskite ferroelectrics. We synthesized and characterized a metal-free dielectric material, MDABCO (N-methyl-N '-diazabicyclo[2.2.2]octonium)(NH4)X3, by substituting the iodide ion (X = I) with nitrate (NO3). Heat capacity measurements conducted with a relaxation calorimeter (PPMS) indicated a phase transition (alpha -> beta) occurring near 273 K. Detailed differential scanning calorimetry (DSC) analysis revealed that the beta-phase is metastable and that a more stable phase (gamma-phase) exists. Single-crystal X-ray diffraction showed that, unlike the iodide analogue, the beta-phase adopts an antiferroelectric structure, attributed to hydrogen-bonding interactions that govern MDABCO molecular orientation. Dielectric measurements further identified a relaxation process in the alpha-phase associated with the rotational dynamics of MDABCO cations, underscoring the critical role of hydrogen bonding in modulating structure and dielectric behavior in all-organic perovskites.

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Structural and Thermal Properties of All-Organic Dielectric Material MDABCO(NH4)(NO3)3

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