Perovskite Cathode Low Work Function Electron Emission

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Solution Overview

Problem

Thermionic electron emitters with volatile surface species limit the lifetime and efficiency of electronic devices due to their high work functions and instability at high temperatures.

Innovation Solution

Transition metal perovskite oxides with low work functions, such as SrVO3, are used as cathodes in electron emitter devices, providing a stable and efficient source of electrons with improved conductivity and longevity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If refractory metals are used as thermionic electron emitters, then stability and electrical conductivity are improved, but work function is high leading to poor electron emission

Engineering Contradiction:

ImprovestabilityVSAvoidwork function

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The patent changes the material composition parameters by incorporating alkaline earth metals (Ba, Sr) and rare earth metals (La, Ce) into the tungsten matrix, creating composite cathode materials with optimized work function and stability. This resolves the contradiction by adjusting material parameters to achieve both low work function and high stability.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent creates composite cathode materials combining refractory metals (W) with alkaline earth metals (Ba, Sr) and rare earth metals (La, Ce). The composite structure allows the refractory metal to provide stability while the alkaline earth and rare earth metals reduce the work function, simultaneously achieving both desired properties.

Inventive Principle:

Principle #40Composite materials

2Use of energy by moving object

If volatile surface species are used to lower work function, then electron emission is improved, but device lifetime is limited due to instability at high temperatures

Engineering Contradiction:

Improvework functionVSAvoiddevice lifetime

Core Design Contradiction:

Use of energy by moving objectVSDuration of action of stationary object

Solution Approach 1:

The patent replaces volatile surface species with stable bulk-composition cathode materials containing alkaline earth and rare earth metals. These materials maintain low work function without requiring volatile coatings, effectively creating a 'disposable-free' solution that eliminates the lifetime limitation while preserving electron emission properties.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

Solution Approach 2:

The patent changes the approach from surface-level work function modification to bulk-composition engineering. By incorporating alkaline earth and rare earth metals into the bulk cathode material, the work function is reduced intrinsically without relying on volatile surface species, thereby improving both electron emission and device lifetime.

Inventive Principle:

Principle #35Parameter changes

3Productivity

If conventional dispenser cathode technologies are used, then electron emission is achieved, but efficiency and longevity are limited

Engineering Contradiction:

Improveelectron emissionVSAvoidefficiency and longevity

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent develops composite cathode materials combining tungsten with alkaline earth metals (Ba, Sr) and rare earth metals (La, Ce). This composite structure maintains high electron emission productivity while improving efficiency and longevity through enhanced thermal stability and reduced material degradation, resolving the contradiction between productivity and reliability.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent optimizes the compositional parameters of the cathode material by varying the ratios of W, Ba, Sr, La, and Ce. This parameter optimization achieves the dual goal of maintaining high electron emission productivity while improving efficiency and longevity through controlled material composition.

Inventive Principle:

Principle #35Parameter changes

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 transition metal perovskite oxides exhibit low work functions, high conductivity, and enhanced stability at high temperatures, leading to improved electron emission and extended device lifetime compared to conventional dispenser cathode technologies.

Implementation Method 1

the transition metal perovskite oxide having a surface from which the mobile electrons are induced to emit upon receiving sufficient energy from an energy source

Methodology Applied

Scientific EffectThermionic emission: Thermionic Emission

Data Source

PatentUS10074505B2Perovskites as ultra-low work function electron emission materials

Publication Date: 2018.09.11 WISCONSIN ALUMNI RES FOUND

AI summary

An electron emitter device is provided comprising a cathode comprising a conductive transition metal perovskite oxide comprising mobile conducting electrons exhibiting a conductivity of at least 10−6 Ω−1-cm−1 at room temperature, the transition metal perovskite oxide having a surface from which the mobile electrons are induced to emit upon receiving sufficient energy from an energy source; and an anode electrically coupled to the cathode and positioned to define an interelectrode conductive region between the anode and the cathode, onto which anode the emitted electrons are collected. The transition metal perovskite oxide may have formula Sr1-xBaxVO3. Related methods and devices based on the electron emitter device are also provided.