Piezoelectric Element With Bismuth Seed Layer for Crystal Alignment
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Solution Overview
Problem
Existing piezoelectric elements using potassium sodium niobate as a lead-free piezoelectric material face challenges in improving electrical characteristics due to element diffusion from the buffer layer into the composite oxide layer during manufacturing, leading to disturbed crystal orientation and reduced performance.
Innovation Solution
A piezoelectric element design with a seed layer containing bismuth and a piezoelectric film incorporating lithium and one or more first transition elements, where the bismuth intensity at the boundary between film regions is limited to 1/500 of the maximum surface intensity, preventing element diffusion and enhancing crystal orientation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a buffer layer containing bismuth, iron, zinc, or nickel is used for the composite oxide layer of potassium sodium niobate, then the crystal orientation of the composite oxide layer is aligned, but the elements in the buffer layer diffuse into the composite oxide layer during heat treatment, disturbing the crystal orientation and deteriorating electrical characteristics
Solution Approach 1:
The patent extracts the harmful diffusion function from the buffer layer by introducing a specific barrier layer containing lithium niobate and transition metal elements (Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn) that selectively blocks element diffusion while maintaining crystal orientation alignment. This separates the alignment function from the diffusion problem.
Solution Approach 2:
The barrier layer acts as an intermediary between the buffer layer and the composite oxide layer. It contains lithium niobate as a base material with transition metal elements that provide both crystal orientation alignment and diffusion barrier functions, preventing harmful element diffusion while maintaining manufacturing precision.
2Ease of manufacture
If the buffer layer elements diffuse into the composite oxide layer during heat treatment, then the crystal orientation is disturbed, but this diffusion is caused by the heat treatment process necessary for manufacturing
Solution Approach 1:
The patent converts the harmful effect of heat treatment-induced diffusion into a beneficial process by using the same heat treatment to activate the diffusion barrier layer. The barrier layer containing lithium niobate and transition metal elements is designed to form during or after heat treatment, utilizing the thermal process to create the protective structure that prevents subsequent harmful diffusion.
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 improved piezoelectric element exhibits enhanced electrical characteristics with reduced leakage current and higher piezoelectric performance, suitable for applications in droplet dispensing and actuation.
Implementation Method 1
a piezoelectric element including: a first electrode formed at a substrate; a seed layer formed at the first electrode; a piezoelectric film containing potassium, sodium, and niobium and formed at the seed layer; and a second electrode formed at the piezoelectric film
Data Source
AI summary
A piezoelectric element includes: a first electrode formed at a vibration plate; a seed layer formed at the first electrode; a piezoelectric film containing potassium, sodium, and niobium and formed at the seed layer; and a second electrode formed at the piezoelectric film. The piezoelectric film contains lithium and one or more first transition elements. The seed layer contains bismuth. When the piezoelectric film is divided into two equal parts in a stacking direction, the second electrode side is defined as a first region, and the first electrode side is defined as a second region, a bismuth intensity obtained by SIMS measurement at a boundary between the first region and the second region is equal to or less than 1/500 of a maximum bismuth intensity obtained by the SIMS measurement of the piezoelectric film.