Modulated Annealing of Single Crystal Oxides for Conductivity

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Solution Overview

Problem

Metal oxides with a 4/m 32/m point group crystal structure exhibit inherently low electrical conductivity, limiting their applications, and existing methods to enhance conductivity, such as doping or forming heterostructures, often suffer from lattice mismatch and impurity incorporation issues.

Innovation Solution

A method involving modulated annealing, where single crystal oxides are alternately exposed to nitrogen and oxygen gases at controlled temperatures to increase conductivity, altering the bulk and surface electronic properties by modifying the number of accessible bonding states.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If doping with transition metals is used to enhance conductivity, then electrical conductivity is improved, but impurity incorporation occurs

Engineering Contradiction:

Improveelectrical conductivityVSAvoidimpurity incorporation

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent applies parameter changes by modulating the oxidation state of metal ions within the oxide lattice through controlled reduction and re-oxidation cycles. This changes the electronic structure and creates charge carriers without introducing foreign impurities, thereby improving conductivity while avoiding contamination

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent uses oxygen partial pressure as an intermediary parameter to control the oxidation state of metal ions. By adjusting the oxygen chemical potential during thermal treatment, the conductivity is tuned through controlled creation of oxygen vacancies and metal ion reduction, without direct introduction of dopant atoms

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If heterostructure formation is used to enhance conductivity, then charge transport is amplified, but lattice mismatch induced strain occurs

Engineering Contradiction:

Improvecharge transportVSAvoidlattice mismatch induced strain

Core Design Contradiction:

ReliabilityVSStress or pressure

Solution Approach 1:

The patent applies local quality by creating localized regions of modified oxidation state within the bulk oxide material. Through controlled reduction, specific metal ions are reduced to lower oxidation states, creating localized electronic pathways for enhanced charge transport while preserving the overall crystal structure and avoiding lattice strain

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

Instead of forming heterostructures by combining different materials, the patent inverts the approach by modifying the oxidation state of existing metal ions within the same material. This creates internal electronic heterogeneity without physical interfaces, eliminating lattice mismatch strain while achieving enhanced charge transport

Inventive Principle:

Principle #13The other way round (Inversion)

3Reliability

If interstitial ions are incorporated to mediate charge transfer, then conductivity is improved, but impurity incorporation occurs

Engineering Contradiction:

Improvecharge transferVSAvoidimpurity incorporation

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent uses oxygen vacancies as an intermediary mechanism for charge transfer. By controlling the oxygen chemical potential during thermal treatment, oxygen vacancies are created or annihilated, which mediate charge transfer between metal ions without requiring foreign interstitial ions. This achieves enhanced conductivity through native defect engineering rather than impurity incorporation

Inventive Principle:

Principle #24Intermediary (Mediator)

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

This approach significantly enhances the electrical conductivity of metal oxides, demonstrated by increased AC conductivity and Raman scattering intensity, with conductive monocrystalline magnesium oxide showing up to an order of magnitude higher conductivity and persistent current density.

Implementation Method 1

A method involving modulated annealing, where single crystal oxides are alternately exposed to nitrogen and oxygen gases at controlled temperatures to increase conductivity

Methodology Applied

Scientific EffectAnnealing: Annealing

Implementation Method 2

contacting the first nitrogen contacted metal oxide with oxygen gas at a temperature in the range of the range of at least ambient temperature to at most 80° C. thereby providing a first oxygen contacted metal oxide

Methodology Applied

Scientific EffectOxidation: Oxidation

Data Source

PatentUS11739438B2Method of producing metal oxides with increased electrical conductivity

Publication Date: 2023.08.29 SHELL USA INC

AI summary

A method for increasing the conductivity of a metal oxide with crystal structure belonging to the 4/m 32/m point group is provided. Single crystal oxides with crystal structure belonging to 4/m 32/m point group are contacted with nitrogen gas, with oxygen gas, with nitrogen gas, with oxygen gas, then with nitrogen gas to increase the conductivity of the metal oxide with crystal structure belonging to the 4/m 32/m point group.