Therefore, dried NFLF powder was uniaxially pressed into pellets (diameter d = 5 mm, thickness h ~ 1 mm) under a force of 0.5 kN. Au blocking electrodes with a thickness of 50 nm were applied on both sides of the pellet with a Leica EM SCD 050 sputter device. EIS was recorded between -60 °C to 240 °C in 10 °C steps using a Novocontrol Concept 80 broadband dielectric spectrometer, covering a frequency range from 10 mHz to 10 MHz. To avoid any influence of oxygen or water, the measurements in the sample cell (BDS 1200, Novocontrol) were controlled by a QUATRO cryosystem (Novocontrol) with a stream of freshly evaporated N 2 gas.