Switchable Nonvolatile Pyroelectric Device Using Asymmetric Electrodes
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Solution Overview
Problem
Conventional pyroelectric devices cannot toggle between persistent pyroelectric and non-pyroelectric states, limiting their application in thermal imaging, sensors, and energy harvesting due to the inability to turn off the pyroelectric response and achieve stable on and off states.
Innovation Solution
A pyroelectric transducer incorporating a polar, antipolar, or nonpolar material with a band gap and pinched or double P-V hysteresis loops, utilizing electrodes with different workfunctions to create a built-in electric field for nonvolatile pyroelectric switches, enabling distinguishable active and inactive states.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a temperature induced phase transition from paraelectric to ferroelectric phase is used, then a giant pyroelectric effect is achieved, but the device requires irreversible polarization with an electric field each time after cooling below the Curie temperature
Solution Approach 1:
The patent utilizes a first-order phase transition between paraelectric and ferroelectric phases that can be reversibly induced by an electric field. The material exhibits a double hysteresis loop with two stable states (paraelectric and ferroelectric phases), allowing the device to switch between pyroelectric active and inactive states through electric field application rather than requiring temperature cycling and field-induced polarization each time.
2Reliability
If electrodes with different workfunctions are used to create a built-in electric field, then nonvolatile pyroelectric states are achieved, but the device structure becomes more complex
Solution Approach 1:
The patent employs asymmetric electrode configuration where the first and second electrodes have different workfunctions. This asymmetry creates a built-in electric field across the material that enables stable, nonvolatile pyroelectric states. The workfunction difference between electrodes is deliberately designed to establish the internal field necessary for maintaining distinguishable active and inactive states without requiring external field application.
3Adaptability or versatility
If a reversible field-induced first-order phase transition is used, then electric field control of polar and nonpolar phases is achieved, but the material requires external electric field application to maintain states
Solution Approach 1:
The patent designs the device so that the built-in electric field from asymmetric electrodes automatically maintains the pyroelectric state without requiring continuous external field application. The material's first-order phase transition characteristics enable it to 'self-maintain' stable polar or nonpolar phases based on the internal field, eliminating the need for ongoing energy input to sustain the desired state.
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
Enables the integration of nonvolatile pyroelectric switches for sensing, detection, and energy harvesting with reduced power consumption, as the device can operate in passive mode without an external electric field, maintaining active or inactive states persistently.
Implementation Method 1
The persistence of a temperature sensitive polar state enables ferroelectrics to exhibit the pyroelectric effect whereby incident electromagnetic radiation, often in the infrared spectrum, is converted into an electric signal.
Implementation Method 2
The application of an electric field can cause the ferroelectric phase to become stable and the paraelectric phase to become metastable or unstable. When the application or removal of an electric field causes a phase transition between a paraelectric and a ferroelectric phase, a reversible field-induced first-order phase transition occurs.
Implementation Method 3
pinched or double P-V hysteresis loops
Data Source
AI summary
Described are thermal-to-electrical signal transducers including band-gap materials with a pinched or double hysteresis loop (DHL) charge-voltage characteristic in a pyroelectric device that have electrically switchable active (on) and inactive (off) pyroelectric states. DHL materials include field induced ferroelectrics (FFE), Kittel-type antiferroelectric (KAFE), defect-biased ferroelectric (DBFE), and ferroelastic switching (FES) materials. The pyroelectric device includes a material stack with a DHL material layer between two electrodes. A built-in electric field is required for the application of the device, which can be induced by electrodes having different workfunctions. Pyroelectric devices employing the DHL material stack include pyroelectric detectors, thermal imaging systems, infrared sensors, and energy harvesters. Nonvolatile pyroelectric switches can replace choppers in uncooled pyroelectric arrays, achieve reprogrammable thermal sensor pixel size and image resolution, and yield infrared detectors with multiple reprogrammable detection paths and spatial scanning of the environment.