Changes over time in ferroelectricity of nanocomposites containing cellulose combined with [NH4][Zn(HCOO)3

Abstract

ABSTRACT For the first time, a composite based on a ferroelectric metal-organic framework of [NH4][Zn(HCOO)3] combined with nanocellulose at different cellulose concentrations from 0 to 75 wt% was synthesised to investigate the changes over time in phase transition and ferroelectric switching. A comparative study for fresh samples and the samples after 288 h was conducted. Electrophysical parameters were measured in a temperature range of 140 to 245 K under a weak electric field with an amplitude of 2 V.cm−1 at a frequency of 1 kHz. The results indicated that the increase in cellulose content led to increasing the phase transition temperature from 190.1 to 238.5 K. Besides, the coercive field was also found to increase from 3.78 to 14.12 kV.cm−1 along with the reduction of dielectric permittivity and maximum polarisation. After 288 h, this phase transition decreased significantly over time even to 231.6 K in the case of highest cellulose content (75 wt%). Meanwhile, the coercive field was found to decrease from 14.12 to 10.57 kV.cm−1. Remarkable changes were detected for samples with cellulose content of higher 25 wt%. The weaker interaction between ferroelectric part and cellulose over time due to the softness of cellulose was responsible for the obtained phenomena.