KNN Piezoelectric Element Sodium Gradient Film Stack
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Solution Overview
Problem
Piezoelectric elements with potassium sodium niobate (KNN) layers formed by wet methods face challenges in achieving homogeneous composition distribution both in-plane and in film thickness directions, affecting their electro-mechanical conversion characteristics and reliability.
Innovation Solution
A piezoelectric element with a KNN layer formed by a wet method, where the first piezoelectric film has a thickness of 30 nm to 70 nm and subsequent films have a sodium concentration gradient from the first electrode side to the second electrode side, ensuring continuous crystal growth and homogeneity in the composition distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a KNN layer is formed by a sputtering method (gas phase method), then the formation process is simple, but the composition distribution (K:Na) cannot be homogenized at the microscopic level and is non-homogeneous in the in-plane direction
Solution Approach 1:
The patent replaces the gas phase sputtering method with a liquid phase wet method (sol-gel process). This substitution allows for homogeneous composition distribution at the microscopic level because the liquid precursor solution can be uniformly applied and dried, forming a homogeneous KNN layer with controlled composition in both in-plane and thickness directions
Solution Approach 2:
The patent changes the physical state parameter of the deposition method from gas phase to liquid phase. By using a liquid precursor solution with controlled composition and applying it through wet coating methods, the patent achieves homogeneous composition distribution that cannot be obtained by conventional sputtering, while still maintaining process simplicity
2Manufacturing precision
If a KNN layer is formed by a wet method (liquid phase method), then the composition distribution in the in-plane direction becomes homogeneous, but the composition distribution in the film thickness direction becomes non-homogeneous
Solution Approach 1:
The patent divides the KNN layer formation into multiple thin films stacked in the film thickness direction. Each thin film has a controlled thickness and composition, and by stacking multiple such films, the overall layer achieves homogeneous composition distribution in both in-plane and thickness directions. This segmentation approach allows precise control of composition at each interface and throughout the bulk
Solution Approach 2:
The patent addresses the composition non-homogeneity in the film thickness direction by introducing the concept of multiple discrete layers. By controlling the thickness and composition of each individual layer and their stacking sequence, the patent achieves three-dimensional compositional homogeneity that cannot be achieved by a single continuous layer formation process
3Reliability
If the first piezoelectric film thickness is increased, then the crystal grain continuity improves, but the composition distribution homogeneity in the film thickness direction deteriorates
Solution Approach 1:
The patent segments the piezoelectric layer into multiple thin films with controlled thickness (e.g., 30-70 nm each). By stacking multiple such thin films, the patent achieves both sufficient crystal grain continuity within each layer and homogeneous composition distribution across the total thickness, as each layer can be independently controlled for composition and thickness
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 results in a piezoelectric element with stable and robust dielectric characteristics, improved electric reliability, and enhanced mechanical robustness against external stress, while maintaining biocompatibility and environmental sustainability.
Implementation Method 1
piezoelectric elements have a piezoelectric layer which has electro-mechanical conversion characteristics
Data Source
AI summary
A piezoelectric element includes a piezoelectric layer formed as a stacked structure of first, second, and third piezoelectric films. The first piezoelectric film is formed on a first electrode. The second piezoelectric film is formed on the first piezoelectric film. The third piezoelectric film is formed on the second piezoelectric film. Each of the first, second, and third piezoelectric films includes potassium, sodium, and niobium. A second electrode is formed on the piezoelectric layer. A concentration of sodium in the first piezoelectric film is greater than a concentration of sodium in the second piezoelectric film. The concentration of sodium in the second piezoelectric film is greater than a concentration of sodium in the third piezoelectric film.