Piezoelectric Element Grain Orientation Control Leakage Current
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Solution Overview
Problem
Existing piezoelectric elements used in liquid ejection heads, such as those in inkjet printers, face challenges in reducing leakage current, which is often attributed to stress and cracking at grain boundaries.
Innovation Solution
The piezoelectric element incorporates a composite oxide with a perovskite structure containing potassium, sodium, and niobium, with specific orientation control: the first layer closest to the first electrode is preferred in a {100} plane orientation in the film thickness direction, while the second layer closest to the second electrode is a mix of {100} and {110} plane orientations in the in-plane direction, avoiding preferred orientations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a piezoelectric layer with random grain orientation is used, then manufacturing is easier, but leakage current increases due to stress and cracking at grain boundaries
Solution Approach 1:
The invention applies different grain orientations to different regions of the piezoelectric layer. Specifically, the grain boundaries are oriented substantially perpendicular to the electrode surfaces, creating a localized quality difference that prevents crack propagation paths while maintaining manufacturing feasibility through controlled deposition processes
Solution Approach 2:
The invention uses a composite structure within the piezoelectric layer by controlling the grain orientation distribution. The layer comprises multiple grains with specific orientation relationships, where grain boundaries are deliberately arranged perpendicular to electrodes, creating a composite microstructure that reduces leakage current while maintaining piezoelectric functionality
2Reliability
If the piezoelectric layer has high density and uniform structure, then reliability improves, but manufacturing precision requirements increase
Solution Approach 1:
The invention changes the orientation parameter of grain boundaries from random to substantially perpendicular alignment with electrode surfaces. This parameter change achieves high density and uniform structure that improves reliability while being attainable through conventional sputtering or chemical solution deposition processes followed by controlled heat treatment
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 configuration effectively reduces leakage current by minimizing stress at grain boundaries and suppressing the formation of crack paths, thereby enhancing the reliability of the piezoelectric element.
Implementation Method 1
a piezoelectric layer provided between the first electrode and the second electrode, the piezoelectric layer including a plurality of layers containing a composite oxide having a perovskite structure containing potassium, sodium, and niobium
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, the piezoelectric layer including a plurality of layers containing a composite oxide having a perovskite structure containing potassium, sodium, and niobium; wherein among the plurality of layers including the composite oxide, a first layer closest to the first electrode is preferred orientation in a first orientation, which is a {100} plane orientation in a film thickness direction, among the plurality of layers including the composite oxide, a second layer closest to the second electrode is, in an in-plane direction intersecting the film thickness direction, a mix of the first orientation and a second orientation, which is a {110} plane orientation, and is not preferred orientation in either the first orientation or the second orientation.