Sintering aid (ZnO) effect on proton transport in BaCe_0.35Zr_0.5Y_0.15O_3‐δ and electrode phenomena studied by distribution function of relaxation times

Abstract

In this work, we have employed an evolutionary programming technique to analyse the impedance spectroscopy (IS) of a ceramic proton conductor BaCe 0.35 Zr 0.5 Y 0.15 O 3-δ (BCZY) to study its proton transport properties as well as the electrode reactions kinetics at the Pt|BCZY interface. The distribution functions of relaxation times (DFRT) obtained from the impedance analysis were used to evaluate the physical parameters such as relaxation time constant, resistance, reactance/capacitance, conductivities, activation energies, grain-boundary space charge potential Φ(0, T), and electrode polarization resistance. The effect of ZnO sintering aid (2 wt%) on charge-transfer processes at bulk, grain boundaries and Pt| BCZY interface were thoroughly studied. Φ(0, T) is increased and grain-boundary conductivity (σ gb ) is decreased by an order of magnitude due to the presence of Zn at the grain boundaries, whereas bulk properties appear to be unchanged. Variation in σ gb with temperature is explained by correlating the grain-boundary capacitance (C gb ), relaxation time (τ gb ), space charge effect, and the defect associations (eg, Y-OH). The anodic functions, for example, hydrogen oxidation kinetics at the electrode (Pt) surface and Pt-BCZY interface, are explained through the symmetrical cell study and the behavior of relaxation time constants (τ) with temperature. K E Y W O R D S

Enhancing the sinterability and electrical properties of BaZr0.1Ce0.7Y0.2O3‐δ proton‐conducting ceramic electrolyte

“…The relaxation time of the grain boundary ( τ gb ) for BZCY at 350°C is 1 × 10 −6 s. Nevertheless, the grain‐boundary arc in Figure 5B is divided into two parts (eg R gb 1 and R gb 2), and the corresponding C values are 1.06 × 10 −8 F and 8 × 10 −8 F, respectively, which are close to the grain‐boundary transport 40,42 . The detailed analysis in the DRT shows that the grain‐boundary response is separated into two peaks: P1 ( τ 1 = 1.59 × 10 −6 s) and P2 ( τ 2 = 1.58 × 10 −5 s) 43 . This phenomenon is caused by the two types of grain boundaries in the BL91 composite material: the first grain boundary originates from the BZCY‐to‐BZCY grain contact and the LSGM‐to‐LSGM grain contact ( R gb 1); the second one comes from BZCY‐to‐LSGM grain contact ( R gb 2).…”

“…40,42 The detailed analysis in the DRT shows that the grain-boundary response is separated into two peaks: P1 (τ 1 = 1.59 × 10 −6 s) and P2 (τ 2 = 1.58 × 10 −5 s). 43 This phenomenon is caused by the two types of grain boundaries in the BL91 composite material: the first grain boundary originates from the BZCY-to-BZCY grain contact and the LSGM-to-LSGM grain contact (R gb 1); the second one comes from BZCY-to-LSGM grain contact (R gb 2). The low-frequency responses represent the electrode processes, the C values are 10 −7 -10 −2 F, and the relaxation times are 10 −4 -1 s, which represents the migration of charge and oxygen diffusion.…”

A Bayesian View on the Hilbert Transform and the Kramers-Kronig Transform of Electrochemical Impedance Data: Probabilistic Estimates and Quality Scores

“…These inductances can be modeled by adding a 0 term to the imaginary part of the impedance, see (5). While the HT of a constant is formally 0, the HT of 0 is infinite.…”

“…Electrochemical impedance spectroscopy (EIS) is one of the most important and versatile techniques of electrochemistry. [1] EIS has been used widely in the fields of energy storage, [2,3] solid-state ionics, [4,5] fuel cells, [6,7] electrolyzers, [8] solar cells, [9,10] porous media, [11] sensors, [12] biology, [13] virological diagnostics, [14] and medicine. [15,16] The EIS technique is particularly appreciated because it can be carried out for frequencies spanning several orders of magnitude, typically from 1 mHz to 10 MHz.…”

A Bayesian View on the Hilbert Transform and the Kramers-Kronig Transform of Electrochemical Impedance Data: Probabilistic Estimates and Quality Scores

“…However, inductive features could also be present in the EIS data. These inductances could be modeled by adding a 0 term to the imaginary part of the impedance, see (5). While the HT of a constant is formally 0, the HT of 0 is infinite.…”