Piezoelectric Element Void Control for Leakage Current

Solution Overview

Problem

Potassium sodium niobate (KNN) thin films formed by solution methods face challenges in achieving improved piezoelectric characteristics while suppressing leakage current, as they often suffer from void formation which deteriorates their electromechanical conversion properties.

Innovation Solution

A piezoelectric element with a KNN-based compound oxide layer, formed using a solution method, is designed to have voids with diameters ≤24 nm and a diameter variation ≤14 nm, reducing leakage current and enhancing piezoelectric characteristics by controlling the number and size of voids in the film.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If the KNN thin film is formed by using the solution method in which high productivity is possible, then productivity is improved, but voids are easily generated which deteriorate piezoelectric characteristics and increase leakage current

Engineering Contradiction:

ImproveproductivityVSAvoidpiezoelectric characteristics

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The invention changes the physical and chemical parameters of the solution method by controlling the concentration ratio of potassium to sodium (K/(K+Na) = 30-70 mol%), the drying temperature (100-200°C), and the baking temperature (600-800°C). These parameter optimizations enable the solution method to produce dense KNN thin films with controlled void structures, achieving both high productivity and reliable piezoelectric characteristics without requiring complex equipment or multiple processing steps

Inventive Principle:

Principle #35Parameter changes

2Productivity

If the KNN thin film is formed by using the solution method in which high productivity is possible, then productivity is improved, but voids are easily generated which increase leakage current

Engineering Contradiction:

ImproveproductivityVSAvoidleakage current

Core Design Contradiction:

ProductivityVSObject-generated harmful factors

Solution Approach 1:

The invention optimizes solution parameters including potassium to sodium concentration ratio (30-70 mol% K), drying temperature (100-200°C), and baking temperature (600-800°C) to control void formation and minimize leakage current while maintaining high productivity through the solution method

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The invention converts the potentially harmful effect of voids into a beneficial controlled structure by specifying that voids should have a maximum diameter of 24 nm or less and a diameter difference of 14 nm or less. This controlled void structure prevents significant leakage current while maintaining the simplicity and high productivity of the solution method, transforming what would normally be a defect into an acceptable and manageable feature

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

3Ease of manufacture

If voids are present in the KNN thin film, then the solution method simplicity is maintained, but piezoelectric characteristics are deteriorated

Engineering Contradiction:

Improveease of manufactureVSAvoidpiezoelectric characteristics

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The invention optimizes solution parameters including potassium to sodium concentration ratio (30-70 mol% K), drying temperature (100-200°C), and baking temperature (600-800°C) to control void formation and minimize leakage current while maintaining high productivity through the solution method

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The invention converts the potentially harmful effect of voids into a beneficial controlled structure by specifying that voids should have a maximum diameter of 24 nm or less and a diameter difference of 14 nm or less. This controlled void structure prevents significant leakage current while maintaining the simplicity and high productivity of the solution method, transforming what would normally be a defect into an acceptable and manageable feature

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

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

This approach effectively suppresses leakage current and improves piezoelectric characteristics, ensuring uniformity and reliability in piezoelectric elements used in devices like ink jet recording heads and other piezoelectric actuator applications.

Implementation Method 1

The piezoelectric layer has electromechanical conversion characteristics

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Data Source

PatentUS10186652B2Piezoelectric element and piezoelectric element applied device

Publication Date: 2019.01.22 SEIKO EPSON CORP

AI summary

There is provided a piezoelectric element which includes a first electrode, a piezoelectric layer which is formed on the first electrode by using a solution method, and is formed from a compound oxide having a perovskite structure in which potassium, sodium, and niobium are provided, and a second electrode which is provided on the piezoelectric layer. A cross-sectional SEM image of the piezoelectric layer is captured at a magnification of 100,000. When evaluation is performed under a condition in which a measured value in a transverse direction is set to 1,273 nm, two or more voids are included in the piezoelectric layer, a difference between the maximum value and the minimum value among diameters of the voids to be largest in a film thickness direction is equal to or smaller than 14 nm, and the maximum value is equal to or smaller than 24 nm.