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

Li et al. (Science Advances, 29 January, p. eabe3068) claim the discovery of two improper ferroelectrics, dabcoHClO(4) and dabcoHBF(4) (dabco = 1,4-diazabicyclo[2.2.2]octane), and that these materials exhibit superior pyroelectric figures of merit. This information is misleading because of the fundamental methodological errors and false conclusions, not to mention that these ferroelectrics were reported more than 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 dabcoHClO(4) and dabcoHBF(4) are about 1000 times lower than the coefficients reported by Li et al.