## 1 Introduction
In cubic pyrochlore structures of PAA, antimony oxide exists in the form of corner-sharing [SbO\({}_{6}\)/2]\({}^{-}\) octahedra connected in the anion skeleton, carrying an excess of negative charge [32]. This charge is compensated by a H\({}^{+}\) proton or by an oxonium ion, H\({}_{3}\)O\({}^{+}\), or by any of the exchangeable cations (Na\({}^{+}\), Sr\({}^{2+}\), Ag\({}^{+}\), etc.). The protons and water molecules can be situated at the center of the hexagonal windows or at the center of the holes formed in the anion skeleton. The charge transfer mechanism of PAA is believed to be the Grot-thuss mechanism (free proton displacement) [33]. Here, protons are displaced along the hydrogen bonds from one water molecule (oxonium ion) to another, in certain crystallographic positions in the PAA structure windows (16(d) and holes 8(b)). However, the existing electrochemical data are controversial and do not fully confirm the suggested mechanism: consequently, the question remains open. Independently, [PERSON] et al. [34] and [PERSON] [32], have reported that the properties of PAA significantly depend on the preparation and aging methodologies. Over the years, studies have been undertaken to obtain information about the electrical and transport properties of PAA [12; 27; 33; 34], all looking for increased: proton conductivity [27; 35]; perm selectivity [29; 34]; chemical structure organization, wide temperature working range, and decreased activation energy [36]. In recent studies conducted by [PERSON] et al. [27; 33], proton conductivity and dielectric losses in PAA and PAA-based membranes were investigated using impedance spectroscopy technique. They showed that the samples had high resistivity, close to dielectric (about 0.5 M\(\Omega\)) behavior, because PAA powder was placed between the electrodes, and not in a bulk membrane. Despite its advantages as a membrane material, PAA cannot be compacted into a bulk membrane without a binder. In the literature, studies of PAA-based membrane compaction using different polymers, such as polyvinyl alcohol (PVA) [27], polysulfone (PSF) [12; 13; 37], polytetrafluoroethylene, poly(vinylidene fluoride) [34; 37], or polyacrylonitrile [38], can be found. Existing results on the proton transport and electrochemical data of such membranes are rather fragmentary and, sometimes, contradictory [27; 30; 34]. In all cases, except for PVA, only film-geometry membranes were obtained. In the films, there is no direct contact between PAA grains, and proton transport cannot be realized through the polyantimonic acid bulk. It certainly contributes to the existing data contradiction. In the study by [PERSON] et al. [27], bulk PAA proton-conducting decorated membranes were fabricated using 80-100 wt.% of PVA as a binder. They found that in the membranes with PAA content lower than 10 wt.%, proton transport was realized through the PVA binder. In addition, and in the presence of moisture, even a low PVA content in the membrane contributed to the total conductivity of the bulk PAA membrane. A complex impedance investigation of transport properties and electrochemical properties could reveal the mechanisms of proton transport in PAA, and thus find consistency in the electrochemical data. For that, the effects of binder content and of the concentration of carrier ions on the electrical response should first be investigated. Thus, the goal of the present work was to investigate binder content and moisture influence on the structure and electrical properties, respectively, of bulk PAA-based membranes, fabricated using an inert binder. Amounts of 10 and 20 wt.% of the inert fluoroplastic binder were used to fabricate bulk PAA membranes and, simultaneously, to ensure the existence of direct contact between grains. An equivalent circuit model describing the material electrical behavior was developed.