Piezoelectric Element Durability via Thermally Stimulated Current Control
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Solution Overview
Problem
Piezoelectric elements used in liquid ejecting heads suffer from durability issues due to oxygen defects and lead defects, which affect their performance over time, leading to changes in liquid ejection conditions.
Innovation Solution
A piezoelectric element with a compound oxide layer containing lead, zirconium, and titanium, having a perovskite crystal structure, is developed, featuring a thermally stimulated current with a low temperature-side peak that is 1/30 or less of the high temperature-side peak, which suppresses leak current and displacement, enhancing durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional piezoelectric element is used in a liquid ejecting head, then the liquid ejection function is achieved, but the durability deteriorates due to oxygen defects and lead defects causing performance changes over time
Solution Approach 1:
The patent applies parameter changes by precisely controlling the ratio of low temperature-side peak to high temperature-side peak in thermally stimulated current (making it 1/30 or less). This parameter control reflects optimized defect distribution in the piezoelectric layer, suppressing oxygen defects and lead defects to maintain stable performance over time, thereby resolving the durability contradiction
Solution Approach 2:
The patent uses a composite piezoelectric layer containing multiple crystal phases (rhombohedral phase and cubic phase in specific ratios) to achieve both durability and performance stability. The composite structure allows optimization of defect characteristics while maintaining piezoelectric functionality, addressing the reliability issue
2Volume of moving object
If the piezoelectric layer is made thinner to form small and thin actuators, then the device size is reduced, but the electro-mechanical conversion efficiency may be affected
Solution Approach 1:
The patent optimizes the thickness of the piezoelectric layer and the ratio of crystal phases within it to achieve high electro-mechanical conversion efficiency in a thin structure. By controlling the rhombohedral-to-cubic phase ratio and optimizing layer thickness, the patent maintains strong piezoelectric response despite reduced dimensions, resolving the contradiction between miniaturization and efficiency
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 results in a piezoelectric element with improved durability and efficient electro-mechanical conversion, capable of long-term stable operation and low-voltage driving, suitable for forming small and thin actuators.
Implementation Method 1
a piezoelectric element which includes a first conductive layer, a second conductive layer which is disposed to face the first conductive layer, and a piezoelectric layer which is disposed between the first conductive layer and the second conductive layer
Data Source
AI summary
A piezoelectric element includes a first conductive layer, a piezoelectric layer, and a second conductive layer. The piezoelectric layer is composed of a compound oxide containing at least lead, zirconium, titanium, and oxygen, and the compound oxide has a perovskite crystal structure. The piezoelectric layer has a thermally stimulated current having at least two peaks including a low temperature-side peak and a high temperature-side peak, and the magnitude of the low temperature-side peak is 1/30 or less of that of the high temperature-side peak.