Piezoelectric Element with Fine-Grain Electrodes for Alkali Diffusion Control
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Solution Overview
Problem
Piezoelectric elements with potassium and sodium-based perovskite structures face challenges in maintaining uniform mechanical properties and adhesion strength due to excessive diffusion of alkali metals, which affects the reliability of liquid ejection heads.
Innovation Solution
A piezoelectric element design featuring a first electrode with platinum group elements and a dense crystal grain structure, and a second electrode with a similar composition, both with average grain diameters of 150 nm or less, effectively traps and suppresses the diffusion of potassium and sodium, maintaining mechanical uniformity and adhesion strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If excess amount of alkali metal elements (potassium and sodium) are charged to improve crystallinity, then the crystallinity is effectively improved, but the alkali metal elements are more liable to diffuse and be swept out of the piezoelectric body, degrading adhesion strength
Solution Approach 1:
A diffusion barrier layer is introduced between the piezoelectric body and the electrode to act as an intermediary that blocks the diffusion path of alkali metal elements. This mediator prevents potassium and sodium from migrating from the piezoelectric body into the electrode, thereby maintaining adhesion strength while allowing excess alkali metals to be present for improved crystallinity.
Solution Approach 2:
The harmful diffusion path is extracted by removing the direct contact interface between the piezoelectric body and electrode. By introducing a separate diffusion barrier layer, the problematic interaction (alkali metal diffusion) is taken out of the system, allowing the piezoelectric body to maintain its composition stability without suffering from adhesion degradation.
2Stability of the object's composition
If alkali metal elements diffuse during crystallization, then the crystallinity is improved, but the mechanical properties of the electrode become non-uniform and the natural frequency uniformity is degraded
Solution Approach 1:
The diffusion barrier layer serves as a mediator that isolates the electrode from alkali metal diffusion during crystallization. This prevents contamination of the electrode with potassium and sodium, ensuring uniform mechanical properties and consistent natural frequency across the piezoelectric element while still allowing excess alkali metals to enhance crystallinity.
3Productivity
If alkali metal elements are present in excess to improve crystallization efficiency, then the crystallinity is improved, but the adhesion between the vibration plate and electrode layer is decreased
Solution Approach 1:
A diffusion barrier layer is positioned between the piezoelectric body and electrode to mediate the interaction. This intermediary allows the piezoelectric body to contain excess alkali metals for high crystallization efficiency while preventing these metals from reaching the electrode interface, thereby maintaining strong adhesion between the vibration plate and electrode layer.
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 solution ensures high piezoelectric characteristics and reliability by preventing excessive diffusion of alkali metals, maintaining uniform mechanical properties and adhesion strength, thereby enhancing the performance of both actuators and sensors.
Implementation Method 1
a piezoelectric element includes a piezoelectric layer having electromechanical conversion characteristics
Data Source
AI summary
A piezoelectric element includes: a first electrode containing crystal grains; a piezoelectric layer which contains potassium, sodium, and niobium and which is provided above the first electrode; and a second electrode provided above the piezoelectric layer, and the average grain diameter of the crystal grains is less than 550 nm.