Lanthanum-Strontium Titanate Interconnects Doped for Low-Temperature Sintering
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Solution Overview
Problem
Lanthanum-doped strontium titanate (LST) interconnect materials for solid oxide fuel cells require high sintering temperatures, making co-firing with YSZ electrolytes challenging, and existing solutions face issues with electrical conductivity and thermal stability.
Innovation Solution
Doping LST with Mn2O3 or Nb2O5 to reduce sintering temperatures and improve sinterability, allowing for co-firing with YSZ electrolytes at lower temperatures while maintaining electrical conductivity and thermal stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If LST materials are sintered at high temperatures (1,460-1,500 °C) to achieve complete densification, then sinterability is improved, but co-firing with YSZ electrolyte becomes difficult due to mismatched sintering temperatures
Solution Approach 1:
The patent applies parameter changes by modifying the sintering temperature parameter through chemical doping. Specifically, Mn2O3 or Nb2O5 dopants are introduced to lower the sintering temperature of LST from 1,460-1,500 °C to a range that enables co-firing with YSZ electrolyte at approximately 1,350 °C, thus resolving the temperature mismatch while maintaining densification
2Adaptability or versatility
If LST materials are doped to reduce sintering temperature, then co-firing with YSZ becomes possible, but electrical conductivity may be compromised
Solution Approach 1:
The patent uses parameter changes by selecting specific dopants (Mn2O3 or Nb2O5) and optimizing their concentrations to achieve a balance between sintering temperature reduction and electrical conductivity maintenance. The dopant levels are carefully controlled to enable co-firing while preserving the necessary electrical properties for interconnect function
3Reliability
If conventional LST materials are used without doping, then electrical conductivity is maintained, but sintering temperature remains too high for co-firing with YSZ electrolyte
Solution Approach 1:
The patent applies composite materials by creating a doped LST system where Mn2O3 or Nb2O5 are incorporated into the LST matrix. This composite approach modifies the sintering behavior and microstructure of the material, enabling lower temperature processing while maintaining or improving the electrical conductivity through controlled defect chemistry and grain boundary engineering
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 doping process effectively reduces sintering temperatures, enhances sinterability, and maintains or improves electrical conductivity and thermal stability, enabling the use of LST materials as interconnects in solid oxide fuel cells.
Implementation Method 1
combining a lanthanum-doped strontium titanate with Mn2O3 or Nb2O5 to form a precursor composition and sintering the precursor composition to form the interconnect
Implementation Method 2
They also exhibit good compatibility with both cathode and anode materials without formation of deleterious second phases
Data Source
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AI summary
An interconnect material is formed by combining a lanthanum-doped strontium titanate with an aliovalent transition metal to form a precursor composition and sintering the precursor composition to form the interconnect material. The aliovalent transition metal can be an electron- acceptor dopant, such as manganese, cobalt, nickel or iron, or the aliovalent transition metal can be an electron-donor dopant, such as niobium or tungsten. A solid oxide fuel cell, or a strontium titanate varistor, or a strontium titanate capacitor can include the interconnect material that includes a lanthanum-doped strontium titanate that is further doped with an aliovalent transition metal.