KNN Piezoelectric Element (001) Orientation for Linear Displacement
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Solution Overview
Problem
Piezoelectric elements based on sodium potassium niobate (KNN) face issues with durability and nonlinear displacement under electric fields, making them unsuitable for actuators and sensors due to cleavage breaking and complex displacement properties.
Innovation Solution
A piezoelectric element with a diffraction peak of the (001) plane at 22.51° to 22.95°, achieved by applying tensile stress to the crystal lattice, ensuring excellent linear displacement properties with respect to applied voltage, and using a KNN-based complex oxide with a composition of (K, Na)NbO3, preferentially oriented to the (100) plane.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single crystal piezoelectric film with specific crystal orientation is used, then piezoelectric properties are improved, but cleavage breaking occurs reducing durability
Solution Approach 1:
The patent changes the crystal orientation parameter from preferential orientation to (100) plane with 2θ of 22.0°-22.4° to preferential orientation to (001) plane with 2θ of 22.51°-22.95°. This parameter change transforms the crystal structure from a configuration prone to cleavage breaking to one that maintains both piezoelectric properties and mechanical durability.
2Reliability
If KNN piezoelectric material near morphotropic phase boundary is used, then piezoelectric effect is enhanced, but nonlinear displacement occurs reducing controllability
Solution Approach 1:
The patent adjusts the compositional parameter x in (KxNa1-x)NbO3 to specific ranges (0.45<x<0.55 or 0.60<x<0.70) and combines it with specific crystal orientation parameters (2θ of 22.51°-22.95° for (001) plane). This dual parameter optimization achieves both enhanced piezoelectric effect and linear displacement characteristics, enabling precise controllability.
3Strength
If polycrystal thin film with (100) plane orientation is used, then mechanical strength is improved, but displacement linearity deteriorates
Solution Approach 1:
The patent changes the crystal orientation parameter from (100) plane with 2θ of 22.0°-22.4° to (001) plane with 2θ of 22.51°-22.95°, and optimizes composition parameter x to specific ranges. This parameter transformation simultaneously achieves mechanical strength and displacement linearity, resolving the contradiction between these two properties.
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 enhances the durability and linearity of displacement in piezoelectric elements, improving their performance in actuator and sensor applications by maintaining stability and reliability under varying voltages.
Implementation Method 1
a piezoelectric element includes a piezoelectric layer including electromechanical conversion properties
Data Source
Figure 1
Figure 2
Figure 3A~3B
AI summary
A piezoelectric element includes a first electrode that is formed on a substrate, a piezoelectric layer that is formed on the first electrode and includes an ABO3 type complex oxide of the perovskite structure expressed by Formula (1) described below, and a second electrode that is formed on the piezoelectric layer, in which the piezoelectric layer is made of a polycrystal which is preferentially oriented to a (100) plane, and has a thickness of 50 nm or more and 2000 nm or less, and in the piezoelectric layer, a diffraction peak position (2θ) of an X-ray derived from the (100) plane of the piezoelectric layer is 22.51° or more and 22.95° or less. (Kx, Na1-x)NbO3 ··· (1)