Perovskite Proton Conductor Composition for Stable High Transport Number
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Solution Overview
Problem
Proton conductors with a perovskite structure face issues with hole conduction in high temperature oxygen atmospheres, leading to increased leakage current and decreased transport number, while adjustments in composition to improve performance can result in unstable crystal structures and reduced conductivity.
Innovation Solution
Incorporating hafnium (Hf) in small amounts into the proton conductor, along with barium (Ba) and yttrium (Y), to stabilize the crystal structure and inhibit hole conduction, thereby improving transport number and maintaining conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the composition of the proton conductor is adjusted to improve performance, then transport number is improved, but crystal structure stability deteriorates and conductivity decreases
Solution Approach 1:
The patent applies parameter changes by precisely controlling the dopant composition ratios (x and y in formula (1)) to optimize both transport number and crystal structure stability. By changing the concentration parameters of Hf and M elements, the patent achieves high transport number (0.80 or more) while maintaining stable perovskite crystal structure through appropriate parameter selection within specified ranges.
Solution Approach 2:
The patent uses composite material strategy by combining multiple elements (A, B, B', M in formula (1)) to create a composite proton conductor with enhanced properties. The composite structure integrates Hf element for high transport number and M element for crystal structure stabilization, achieving synergistic effects that resolve the contradiction between transport number improvement and structural stability.
2Reliability
If hafnium is introduced to inhibit hole conduction, then transport number is improved, but conductivity may decrease due to crystal structure instability
Solution Approach 1:
The patent introduces M element as an intermediary that mediates between Hf element and the crystal structure. While Hf inhibits hole conduction and improves transport number, M element acts as a stabilizing intermediary that prevents excessive crystal structure distortion, thereby maintaining conductivity. This intermediary approach resolves the contradiction by allowing Hf's beneficial effect while mitigating its harmful side effect.
Solution Approach 2:
The patent controls the concentration parameter of Hf element (x in formula (1)) within a specific range to optimize the balance between hole conduction inhibition and crystal structure stability. By precisely adjusting this parameter, the patent achieves high transport number while preventing excessive conductivity decrease that would result from uncontrolled Hf addition.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The approach enhances transport number while suppressing conductivity decreases, leading to improved performance in fuel cells and water electrolysis devices by stabilizing the crystal structure and inhibiting hole conduction.
Implementation Method 1
hafnium (Hf) inhibits Hole conduction, the transport number is improved
Implementation Method 2
Oxides such as barium zirconate (BZY) which has a perovskite structure and to which yttrium is added exhibit good proton conductivity
Data Source
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AI summary
Provided is a proton conductor that achieves an improvement in transport number while suppressing a decrease in conductivity. The proton conductor contains a metal oxide having a perovskite structure and represented by formula (1): AaB1-x-yB'xMyO3-δ (1), wherein an element A is at least one element selected from the group consisting of Ba, Sr, and Ca, an element B is at least one element selected from the group consisting of Zr and Ce, an element B' is Hf, an element M is at least one element selected from the group consisting of Y, Yb, Er, Ho, Tm, Gd, In, and Sc, δ is an oxygen deficiency amount, and "a", "x", and "y" satisfy 0.9≤a≤1.0, 0.1≤y≤0.2, and 0<x/(1-y)≤0.2.