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Solid state ion transport and phase behaviour in composites of N,N-methyl propylpyrrolidinium tetrafluoroborate and amorphous polyethylene oxide
journal contributionposted on 01.01.2003, 00:00 authored by J Efthimiadis, G Annat, Jim Efthimiadis, Maria ForsythMaria Forsyth, D MacFarlane
The binary and ternary addition of 2 wt.% LiBF4 and 2 wt.% amorphous polyethylene oxide (aPEO) respectively to the plastic crystal forming salt P13BF4 (where P13+=methylpropyl pyrrolidinium cation) was investigated with specific focus on the phase behaviour and evaluation of transport characteristics. Differential scanning calorimetry (DSC), optical thermomicroscopy, solid state nuclear magnetic resonance (NMR), and AC impedance spectroscopy were used to develop an understanding of the conduction process in the pure and mixed systems. The morphology of the ternary compound appeared as hexagonal spherulites upon solidification. Multinuclear NMR Pulsed Field Gradient measurements (1H,19F,7Li) to probe both cation and anion diffusion coefficients are reported. The anion is shown to be the most diffusive (at 320 K:19F=2.5×10−11 m2 s−1; 1H: 1.8×10−11 m2 s−1; 7Li: 1.1×10−11 m2 s−1) in the ternary compound, with enhanced conductivity (2.7×10−5 S cm−1 at 310 K) just below the melt.