CaMnO3 Thermoelectric Ceramic Doping and Liquid Phase Sintering
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Solution Overview
Problem
Transition metal oxides, particularly CaMnO3, exhibit low thermoelectric energy conversion efficiency due to their low power factor, which is challenging to improve without simultaneously decreasing the Seebeck coefficient and electrical conductivity.
Innovation Solution
Introducing a metal oxide liquid phase during sintering and modifying the chemistry of precursor materials by doping CaMnO3 with elements from group 13, 14, 15, 16, or rare earth elements, such as bismuth and copper, to create a grain boundary phase that enhances the electrical power factor and decouples the Seebeck coefficient from electrical conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If carrier concentration is increased to improve power factor, then electrical conductivity increases, but overall power factor improvement is limited
Solution Approach 1:
The patent applies local quality by creating different phases with different properties in different locations: the bulk CaMnO3 matrix maintains stoichiometric or lightly doped composition for high Seebeck coefficient, while the grain boundary regions contain metal oxide liquid phases for high electrical conductivity. This spatial differentiation of material properties allows optimization of power factor without requiring uniform heavy doping throughout the entire material.
2Adaptability or versatility
If transition metal oxides are used for thermoelectric applications, then environmental friendliness and mass production potential are improved, but energy conversion efficiency deteriorates
Solution Approach 1:
The patent fundamentally changes the physical state parameter of the grain boundary phase from solid to liquid by introducing metal oxides with lower melting points (such as CuO, NiO, CoO) into the CaMnO3 matrix. This parameter change creates a liquid phase at operating temperatures that provides exceptional electrical conductivity, enabling transition metal oxides to achieve heavy metal-level power factors while maintaining their environmental benefits and mass production advantages.
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 significantly increases the energy conversion efficiency of CaMnO3, achieving a ZT value of 0.67 at 773 K, which is twice that of previously reported values, with a high power factor of 2.4 mWm−1K−2 and improved mechanical toughness, making it suitable for wide temperature range applications.
Implementation Method 1
The thermoelectric effect is one of the simplest energy conversion technologies converting a temperature difference directly into the electricity
Implementation Method 2
Introducing a metal oxide liquid phase during sintering and modifying the chemistry of precursor materials
Data Source
AI summary
In one aspect, the disclosure relates to thermoelectric ceramic oxide compositions comprising a CaMnO3 ceramic. In a further aspect, the disclosed thermoelectric ceramic oxide compositions can dramatically increase the energy conversion efficiency of thermoelectric through a combination of modifying the chemistry of precursor materials, and simultaneously introducing a metal oxide liquid phase during sintering. In a further aspect, the present disclosure pertains to thermoelectric ceramic oxide compositions comprising a metal doped CaMnO3 having with a metal oxide grain boundary phase; wherein the metal is selected from group 13, group 14, group 15, group 16, or a rare earth element. In a still further aspect, the disclosure relates to methods for making the thermoelectric ceramic oxide materials. This abstract is intended as a scanning tool for purposes of searching in the particular art and is not intended to be limiting of the present disclosure.