Piezoelectric Composite Articles with Modulus-Contrast Conductive Layers
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Solution Overview
Problem
There is a need for improved piezoelectric materials and methods to enhance the piezoelectric coefficients, particularly the d33 charge coefficient, in order to improve the performance of piezoelectric devices, as existing materials like lead zirconate titanate pose environmental and health concerns, and current methods fail to achieve high sensitivity and stability in thick or thin film devices.
Innovation Solution
A composite article comprising a dry piezoelectric layer with one or more dry electrically-conductive layers containing particles with a different Young's modulus, distributed uniformly, which affects the stress distribution and enhances the piezoelectric response by improving the d33 charge coefficient without relying on the device's structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If lead zirconate titanate (PZT) is used as piezoelectric material, then piezoelectric performance is improved, but environmental and health concerns arise
Solution Approach 1:
The patent changes the material composition parameters by replacing lead-based PZT with lead-free alternatives such as barium titanate (BaTiO3), strontium titanate (SrTiO3), or their mixtures. This substitution maintains acceptable piezoelectric performance while eliminating the harmful lead content, thus resolving the contradiction between performance and environmental safety.
Solution Approach 2:
The patent employs composite material structures by combining lead-free piezoelectric materials with polymer matrices (such as PVDF, PVDF-TrFE, or PVDF-HFP) to create piezoelectric composite articles. These composites achieve the desired piezoelectric coefficients through the synergistic effect of the ceramic particles and polymer matrix, providing both performance and environmental compliance.
2Productivity
If thick or thin film piezoelectric devices are manufactured, then device integration is improved, but high sensitivity is difficult to achieve
Solution Approach 1:
The patent applies local quality enhancement by incorporating discrete piezoelectric particles (5-500 micrometers in size) into the polymer matrix, creating localized regions of high piezoelectric activity. This particle-reinforced composite structure provides enhanced sensitivity at specific locations within the film, allowing thick or thin film devices to achieve high sensitivity regardless of overall thickness.
Solution Approach 2:
The patent uses composite materials combining piezoelectric ceramic particles with flexible polymer matrices to create piezoelectric films that maintain high sensitivity across different thicknesses. The composite structure allows the material to exhibit both the high piezoelectric coefficients of ceramics and the flexibility of polymers, enabling sensitive responses in both thick and thin film configurations.
3Stability of the object's composition
If piezoelectric particles are dispersed in polymer matrix, then flexibility is improved, but piezoelectric coefficients are reduced
Solution Approach 1:
The patent optimizes the parameter of particle size (5-500 micrometers) and particle concentration (1-90 weight percent) to achieve a balance between flexibility and piezoelectric coefficients. By carefully controlling these parameters, the composite maintains the flexibility of the polymer matrix while incorporating sufficient piezoelectric particles to achieve high d33 coefficients (20-500 pC/N).
Solution Approach 2:
The patent employs composite material design where piezoelectric ceramic particles are dispersed in a flexible polymer matrix (PVDF, PVDF-TrFE, or PVDF-HFP). The composite structure leverages the flexibility of the polymer while the dispersed particles provide high piezoelectric coefficients, achieving both desired properties simultaneously through proper material selection and formulation.
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 composite article design significantly enhances the piezoelectric response of both polymers and ceramics, enabling improved performance in devices such as energy harvesters, sensors, and capacitors by directly manipulating the d33 charge coefficient, offering a more stable and efficient solution compared to existing technologies.
Implementation Method 1
Piezoelectric materials are materials that can generate charge and provide voltage when placed under mechanical stress ('piezoelectric effect')
Implementation Method 2
the (b) particles having a Young's modulus that is different from the Young's modulus of the (a) electrically-conductive material by at least 10%, and which (b) particles have a d50 of at least 500 nm and up to and including 500 μm
Data Source
AI summary
A composite article is designed for use in various devices and to exhibit improved piezoelectric effects. The composite article has 1) a dry piezoelectric layer (first dry PL) comprising a piezoelectric material, and 2) a dry electrically-conductive layer arranged contiguously with an opposing surface of the first dry PL. The dry electrically-conductive layer essentially has (a) an electrically-conductive material; and (b) particles having a Young's modulus that is different from the Young's modulus of the (a) electrically-conductive material by at least 10%, and which (b) particles have a d50 of at least 500 nm and up to and including 500 μm and a polydispersity coefficient that is less than or equal to 3. The weight ratio of the (b) particles to the (a) electrically-conductive material is at least 0.01:1 and up to and including 10:1.