Colossal Dielectric Response and Electric Polarization in Lithium Nitrate

Abstract

Lithium nitrate LiNO$_3$ is identified to possess a dielectric constant $\epsilon$' larger than 6x10$^6$ at 1 kHz in powder samples above the critical temperature $T$$_W$ = 306 K. For single crystalline samples, $\epsilon$' can be sustained to remain above 10$^5$ and the dissipation factor below 10 in the temperature region of 280-340 K after a simple 'activation' process. Moreover, pyroelectric current measurements show LiNO$_3$ to be ferroelectric with an electric polarization of $P$ = 1,200 $\mu$C/cm$^2$. Both $\epsilon$' and $P$ are amongst one of the highest in all known materials. We propose a model suggesting the mechanism underlying the colossal magnitudes of $\epsilon$' and $P$ to stem from a gearing-ungearing process of the planar NO$_3$$^-$ at the macroscopic level. Our results potentially push the boundaries of ceramic capacitors.