Piezoelectric Element Adhesion Layer for Inkjet Heads
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Solution Overview
Problem
Piezoelectric elements with high piezoelectric constants used in ink jet recording heads face issues with durability and leakage current, particularly when subjected to heat treatments, due to poor adhesiveness between the piezoelectric film and upper electrode, and increased oxygen defects.
Innovation Solution
A piezoelectric element with a perovskite structured film represented by Pb[(ZrxTi1-x)1-y]O3, where x<1 and y between 0.10 and 0.13, and an adhesion layer with a metal ionization energy of 0.34 eV or less, ensuring a peak intensity ratio of 0.85≤I(200)/I(100)≤1.00, which enhances adhesion and suppresses leakage current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If highly stable Ir or Pt is used for the upper electrode, then electrode stability is improved, but adhesiveness between the piezoelectric film and upper electrode deteriorates, resulting in peeling-off
Solution Approach 1:
An adhesion layer is introduced as an intermediary between the piezoelectric film and the upper electrode. This adhesion layer serves as a mediator that provides both adhesion to the piezoelectric film and compatibility with the stable electrode material (Ir or Pt), thereby resolving the contradiction between electrode stability and adhesiveness.
Solution Approach 2:
The electrode structure is designed as a composite system consisting of multiple layers: the piezoelectric film, an adhesion layer with specific composition, and the upper electrode material. This composite structure combines the advantages of different materials to achieve both strong adhesion and high stability.
2Reliability
If Nb content is increased to improve piezoelectric performance, then piezoelectric characteristics are improved, but leakage current increases after heat treatment
Solution Approach 1:
The patent optimizes the Nb content parameter within a specific range (0.10≤y≤0.13) and controls the peak intensity ratio I(200)/I(100) within 0.85≤I(200)/I(100)≤1.00. By precisely controlling these parameters, the patent achieves good piezoelectric characteristics while suppressing leakage current after heat treatment.
Solution Approach 2:
The patent introduces an adhesion layer with specific local composition and properties between the piezoelectric film and electrode. This layer has localized functional characteristics that differ from the bulk piezoelectric material, providing improved adhesion and suppression of leakage current at the interface region.
3Strength
If adhesion layer with easily oxidizable material is used, then adhesiveness is improved, but leakage current increases after heat treatment
Solution Approach 1:
The patent changes the compositional parameters of the adhesion layer, specifically controlling the metal content and ionization energy (0.34 eV or less). This parameter optimization allows the adhesion layer to provide strong adhesion while maintaining low leakage current even after 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
The solution maintains good piezoelectric characteristics and effectively suppresses leakage current in piezoelectric elements, even after heat treatments, by optimizing the composition and structure of the piezoelectric film and adhesion layer.
Implementation Method 1
a piezoelectric film that expands or contracts according to an increase or decrease in intensity of an applied electric field
Implementation Method 2
an adhesion layer is arranged between the piezoelectric film and the upper electrode
Data Source
AI summary
A piezoelectric element includes a substrate, and a lower electrode, a piezoelectric film, an adhesion layer, and an upper electrode provided on the substrate in this order, in which the piezoelectric film has a perovskite structure that is preferentially oriented to a (100) plane and is a composite oxide represented by the compositional formula Pb[(ZrxTi1-x)1-yNby]O3, where x satisfies 0<x<1 and y satisfies 0.10≤y<0.13, I(200)/I(100), which is a ratio between a diffraction peak intensity I(100) from the perovskite plane and a diffraction peak intensity I(200) from a perovskite plane as measured by X-ray diffraction method, satisfies 0.85≤I(200)/I(100)≤1.00, and the adhesion layer contains a metal having an ionization energy of 0.34 eV or less.