Piezoelectric Element With Controlled Atom Concentration
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Solution Overview
Problem
Piezoelectric elements with potassium sodium niobate (KNN) layers face cracking issues when the thickness is increased, due to variations in sodium and potassium atom concentrations leading to stress and reduced toughness.
Innovation Solution
A piezoelectric element with a KNN layer having a perovskite structure, where the standard deviation of sodium and potassium atom concentrations in specific regions is controlled to 0.140 or less and 0.070 or less respectively, reducing the likelihood of cracking by maintaining continuity and reducing stress in the crystal lattice.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the thickness of the piezoelectric layer is increased, then the electromechanical conversion performance is improved, but cracking occurs in the piezoelectric layer due to stress from atom concentration variations
Solution Approach 1:
The patent applies parameter changes by precisely controlling the atom concentration parameters (standard deviation of sodium and potassium atom concentrations) within the piezoelectric layer. By maintaining the standard deviation of sodium atom concentrations at 0.140 or less and potassium atom concentrations at 0.070 or less, the material properties are optimized to prevent cracking while enabling increased layer thickness for improved electromechanical performance.
Solution Approach 2:
The patent applies local quality by ensuring uniform atom concentration distribution throughout the piezoelectric layer. The specific regions defined in the patent (eight regions including central lines) require controlled atom concentrations, creating localized quality control that prevents stress concentration and cracking while maintaining overall layer integrity for enhanced performance.
2Power
If the thickness of the piezoelectric layer is increased, then the electromechanical conversion performance is improved, but the mechanical stability and toughness are reduced due to stress from atom concentration variations
Solution Approach 1:
The patent changes the chemical composition parameters by controlling the standard deviation of sodium and potassium atom concentrations to specific values (0.140 or less for sodium, 0.070 or less for potassium). This parameter control reduces internal stress and improves mechanical stability, allowing thicker layers to maintain both enhanced electromechanical performance and sufficient toughness.
Solution Approach 2:
The patent applies beforehand cushioning by pre-controlling atom concentration distributions during the formation process. By establishing uniform concentration profiles before the layer is fully formed, the patent prevents stress concentration that would otherwise cause cracking and mechanical failure, enabling thicker layers to maintain mechanical integrity.
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 controlled atom concentration distribution suppresses cracking in the piezoelectric element, enhancing its mechanical stability and reliability, particularly when the thickness of the KNN layer is increased.
Implementation Method 1
a piezoelectric element includes a piezoelectric layer that exhibits electromechanical conversion characteristics
Data Source
AI summary
A piezoelectric element includes: a first electrode and a second electrode; and a piezoelectric layer provided between the first electrode and the second electrode, where: the piezoelectric layer contains a complex oxide having a perovskite structure and including potassium, sodium, and niobium; on a cross-section of the piezoelectric layer, a standard deviation of values that are obtained by normalizing sodium atom concentrations in eight regions by an average value of the sodium atom concentrations in the eight regions is 0.140 or less; each of the regions includes a central line of the piezoelectric layer; each of the regions is a square having a size in a thickness direction of the piezoelectric layer and a size in a direction orthogonal to the thickness direction of 150 nm; and the eight regions are aligned in the direction orthogonal to the thickness direction.