Piezoelectric Element Defect Engineering for Liquid Ejecting Heads
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Solution Overview
Problem
Piezoelectric elements, particularly those composed of PZT thin films, experience degradation due to prolonged exposure to voltage pulses, leading to a decrease in device properties and reduced durability in liquid ejecting heads and other devices.
Innovation Solution
A piezoelectric element with a metal oxide layer containing lead (Pb), zirconium (Zr), and titanium (Ti) is developed, featuring a higher concentration of negatively charged Pb-O complex defects than positively charged defects, which are detected at specific energy levels, enhancing durability by minimizing degradation even under long-term voltage exposure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If piezoelectric elements are used in liquid ejecting heads, then device functionality is achieved, but degradation occurs due to prolonged voltage pulse exposure
Solution Approach 1:
The patent changes the chemical composition parameters of the piezoelectric material by intentionally introducing Pb-O complex defects with specific concentration ratios. The negatively charged Pb-O complex defects are maintained at higher concentrations than positively charged defects, which fundamentally alters the material's electrical and mechanical properties to resist degradation from prolonged voltage exposure.
Solution Approach 2:
The invention creates a composite defect structure within the piezoelectric material by combining multiple types of Pb-O complex defects (negatively charged and positively charged) in specific proportions. This composite defect configuration provides synergistic effects that enhance overall device reliability and durability under operational conditions.
2Ease of manufacture
If piezoelectric material layer is formed uniformly over the entire surface, then manufacturing is simplified, but device properties degrade over time
Solution Approach 1:
While maintaining uniform formation process simplicity, the invention introduces localized variations in defect concentration and distribution within the piezoelectric material. The Pb-O complex defects are distributed with specific concentration gradients and spatial patterns that enhance local resistance to degradation while preserving overall manufacturing simplicity.
3Reliability
If excessive lead content is adjusted to optimize piezoelectric constant, then device performance improves, but manufacturing precision requirements increase
Solution Approach 1:
The patent transforms the manufacturing approach by shifting from precise control of total lead content to control of Pb-O complex defect characteristics. This parameter transformation allows achieving optimal piezoelectric performance through defect engineering rather than strict compositional control, thereby reducing manufacturing precision requirements while maintaining high device performance.
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 increased concentration of negatively charged Pb-O complex defects improves the durability of piezoelectric elements, reducing degradation rates and maintaining device performance over time, resulting in a more reliable liquid ejecting apparatus.
Implementation Method 1
a piezoelectric layer composed of a piezoelectric material having an electromechanical conversion function
Implementation Method 2
the negatively charged Pb-O complex defects are detected at an energy level of 1.3 eV, and the positively charged Pb-0 complex defects are detected at an energy level of 2.0 eV by a thermally stimulated current technique
Data Source
Figure 1
Figure 2A~2B
Figure 3
AI summary
A liquid ejecting head includes a pressure-generating chamber communicating with a nozzle opening, and a piezoelectric element which includes a first electrode, a piezoelectric layer disposed on the first electrode, and a second electrode disposed on the piezoelectric layer. The piezoelectric layer is composed of a metal oxide containing lead (Pb), zirconium (Zr), and titanium (Ti), and has negatively charged Pb-O complex defects and positively charged Pb-O complex defects, the concentration of the negatively charged Pb-O complex defects being higher than the concentration of the positively charged Pb-O complex defects.