Piezoelectric Element Compressive Stress Second Electrode
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Solution Overview
Problem
Piezoelectric elements formed by the liquid phase method suffer from low displacement efficiency due to tensile stress, which deteriorates the characteristics of the piezoelectric layer and results in small displacement amounts.
Innovation Solution
A piezoelectric element with a first electrode, a piezoelectric layer of composite oxide with a perovskite structure preferentially oriented in the (100) plane, and a second electrode of platinum also oriented in the (100) plane, where the second electrode is film-formed on the piezoelectric layer to apply compressive stress, reducing tensile stress and enhancing displacement efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a piezoelectric layer is formed by a liquid phase method, then the manufacturing process is simple and cost-effective, but the piezoelectric layer is subjected to tensile stress which deteriorates its characteristics and reduces displacement efficiency
Solution Approach 1:
The invention changes the stress state parameter of the piezoelectric layer from tensile to compressive by introducing a second electrode that applies compressive stress. This parameter change resolves the contradiction by maintaining the simple liquid phase manufacturing method while improving the piezoelectric layer characteristics and displacement efficiency through stress state modification.
2Ease of manufacture
If a piezoelectric layer is formed by a liquid phase method, then the manufacturing cost is low, but the displacement amount is small due to tensile stress
Solution Approach 1:
The invention modifies the stress parameter from tensile to compressive by adding a second electrode, which directly increases the displacement amount of the piezoelectric element while maintaining the cost-effective liquid phase manufacturing method for the piezoelectric layer.
3Reliability
If a second electrode is film-formed on a piezoelectric layer by lattice matching, then compressive stress is applied to reduce tensile stress, but the manufacturing process becomes more complex
Solution Approach 1:
The second electrode acts as an intermediary element that applies compressive stress to the piezoelectric layer through lattice matching. This intermediary structure resolves the contradiction by improving piezoelectric layer characteristics while adding only a single film-forming step to the manufacturing process.
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 approach improves the characteristics of the piezoelectric layer, resulting in a piezoelectric element with high displacement efficiency and environmental benefits by using bismuth and iron in the A-site and B-site, respectively.
Implementation Method 1
changing the pressure of a liquid in the pressure generating chambers by deforming piezoelectric elements (piezoelectric actuators)
Implementation Method 2
after the film-forming, compressive stress is applied to the piezoelectric layer in an in-plane direction, the tensile stress in the in-plane direction, which the piezoelectric layer had before film-forming the second electrode, is reduced
Data Source
AI summary
A piezoelectric element includes a first electrode, a piezoelectric layer which is provided on the first electrode and which is formed of crystals of a composite oxide with a perovskite structure which is preferentially oriented in a plane, and a second electrode which is provided on the piezoelectric layer and which is formed of platinum which is preferentially oriented in a plane, in which, in the piezoelectric layer, plane intervals L1 of the crystals on the first electrode side are larger than plane intervals L2 of the crystals on the second electrode side.