Electrical relaxation in proton conductor composites based on (NH4)H2PO4/TiO2

Abstract

We report on electrical relaxation measurements of (1 − x)NH 4 H 2 PO 4 -xTiO 2 (x = 0.1) composites by admittance spectroscopy, in the 40-Hz-5-MHz frequency range and at temperatures between 303 and 563 K. Simultaneous thermal and electrical measurements on the composites identify a stable crystalline phase between 373 and 463 K. The real part of the conductivity, σ ', shows a power-law frequency dependence below 523 K, which is well described by Jonscher's expression σ = σ 0 (1 + (ω/ω p ) n ), where σ 0 is the dc conductivity, ω p /2π = f p is a characteristic relaxation frequency, and n is a fractional exponent between 0 and 1. Both σ 0 and f p are thermally activated with nearly the same activation energy in the II region, indicating that the dispersive conductivity originates from the migration of protons. However, activation energies decrease from 0.55 to 0.35 eV and n increases toward 1.0, as the concentration of TiO 2 nanoparticles increases, thus, enhancing cooperative correlation among moving ions. The highest dc conductivity is obtained for the composite x = 0.05 concentration, with values above room temperature about three orders of magnitude higher than that of crystalline NH 4 H 2 PO 4 (ADP), reaching values on the order of 0.1 ( cm) −1 above 543 K.

Study of dc conductivity, transport mechanism, and dielectric relaxation in cassava starch membranes plasticized with glycerol

“…At low frequencies, a line adjacent to the arc was observed, attributed to charge transference on the interface of the sample electrode. Similar results were obtained for the G/S=0.4 and G/S=0.5 membranes [11,21,22].…”

“…The study of relaxation and of its behavior permits gathering information about its nature, the types of molecular movements, and how they are affected by the structure, chemical composition, and morphology; while through ac conductivity, the nature of the conduction process in systems is characterized [11].…”

New composites of ZnO–P2O5/Ni having PTC transition and high Seebeck coefficient

“…6a) at high temperature (T ≥ 370 K). The conduction is thermally activated and follows an Arrhenius type law with the activation energy about 0.6 eV, in good agreement with values obtained in similar phosphate materials [42,43]. This means that the conduction mechanisms are associated to the movement of carriers in delocalized states outside the gap between mobile and localized states near the Fermi level E F .…”

Conductividad iónica en nuevos compositos (PEO)10(CF3COONa)-X % Al2O3

“…Parámetros Arrhenius y VTF en la región III (de 390K hasta 430K) para: PEO puro y diferentes concentraciones (X) del composito (PEO) 10 (CF 3 COONa)) -X% Al 2 O 3 . sal es debida a reacciones de Lewis acido-base que forman el complejo entre el electrolito y las partículas cerámicas, formando centros de entrecruzamientos en la matriz polimérica y disminuyendo la cristalinidad del sistema (Castillo et al 2009, Syzdek et al 2010.…”

“…Si la interface entre las partículas de relleno y el polímero cristalino es amorfa, y es predominante en el composito, el trasporte iónico se interpreta como un estado modelo amorfo, el cual se asemeja a los modelos de carga espacial desarrollados para compositos sal-cerámicos (Pritula et al 2013, Castillo et al 2009). En estos modelos, la adición de partículas cerámicas, lleva a la formación de caminos de alta conducción en la interface amorfa y la conductividad se incrementa.…”