Comment on Improper molecular ferroelectrics with simultaneous ultrahigh pyroelectricity and figures of merit by Li et al

TL;DR

This paper critically examines claims of improper ferroelectrics with ultrahigh pyroelectricity, revealing methodological errors and clarifying that the materials are proper ferroelectrics with significantly lower pyroelectric coefficients than previously reported.

Contribution

It corrects misconceptions by demonstrating that the materials are proper ferroelectrics and highlights the substantial overestimation of pyroelectric figures of merit in prior work.

Findings

Li et al.'s materials are proper ferroelectrics, not improper.

Reported pyroelectric coefficients are about 103 times lower.

The original claims of ultrahigh pyroelectricity are based on methodological errors.

Abstract

Li et al. (Science Advances, 29 January, p. eabe3068) claim the discovery of two improper ferroelectrics, dabcoHClO4 and dabcoHBF4 (dabco = 1,4-diazabicyclo[2.2.2]octane), and that these materials exhibit superior pyroelectric figures of merit. This information is misleading due to the fundamental methodological errors and false conclusions, not to mention that these ferroelectrics were reported over 20 years ago. They are proper ferroelectrics, for which the spontaneous polarization is the macroscopic order parameter. We show that the useful pyroelectric coefficients of these materials are about 103 times lower than these reported by Li et al.