Lead-Free Piezoelectric Thin-Film Multilayer Body
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Solution Overview
Problem
Current piezoelectric thin-film devices with lead-free materials face challenges in achieving consistent piezoelectric properties and reliability due to variations in crystal grain boundaries and high production costs, particularly in multilayer structure control and surface roughness management.
Innovation Solution
A piezoelectric thin-film multilayer body is developed with a substrate, an adhesive layer, a lower electrode layer, and a lead-free piezoelectric thin-film layer, where the adhesive layer is composed of a non-crystalline oxide with a thickness between 1 nm and 2 nm, and the substrate's surface roughness is controlled to ensure optimal crystal orientation and reduced variations, using materials like titanium oxide and platinum electrodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a thin-film deposition technique is used to reduce device size, then the thickness of the piezoelectric material can be reduced to 10 μm or less, but the crystal grain boundaries significantly affect piezoelectric property causing large variations among devices
Solution Approach 1:
The invention changes the material composition parameters by using a specific lead-free piezoelectric material with formula (1-x)y-(1-y)Pb(Mg3Nb2/3)O3-PbTiO3 where 0.94≤x<0.98 and 0.06≤y<0.10, and controls the crystal grain size to be 0.5 μm or less. This material parameter optimization resolves the contradiction by achieving consistent piezoelectric properties even at thin film thicknesses of 10 μm or less.
2Length of moving object
If the thickness of the piezoelectric material is reduced to improve device miniaturization, then the device size is reduced, but the effect of crystal grain boundaries cannot be ignored causing variations in piezoelectric property
Solution Approach 1:
The invention optimizes material composition parameters with specific ranges for x and y in the formula (1-x)y-(1-y)Pb(Mg3Nb2/3)O3-PbTiO3, and controls crystal grain size to 0.5 μm or less. These parameter changes ensure reliable and consistent piezoelectric properties even when the material thickness is reduced to 10 μm or less, resolving the contradiction between miniaturization and reliability.
3Ease of manufacture
If conventional powder sintering method is used, then piezoelectric material can be produced, but when thickness is 10 μm or less, crystal grain boundary effects cause significant variations in piezoelectric properties
Solution Approach 1:
The invention changes the material parameters by selecting specific composition ranges for the lead-free piezoelectric material and controlling crystal grain size to 0.5 μm or less. This enables the use of conventional powder sintering method while achieving uniform piezoelectric properties even at thicknesses of 10 μm or less, resolving the contradiction between ease of manufacture and manufacturing precision.
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 configuration enhances the piezoelectric properties and reduces variations among devices, achieving a high degree of crystal orientation and stability while minimizing production costs by maintaining surface flatness and controlling the adhesive layer's thickness and substrate roughness.
Implementation Method 1
A piezoelectric device is a device that utilizes the piezoelectric effect of a piezoelectric material
Implementation Method 2
a piezoelectric thin-film multilayer body includes a substrate, an adhesive layer on the substrate, a lower electrode layer on the adhesive layer, and a lead-free piezoelectric thin-film layer on the lower electrode layer
Data Source
AI summary
A piezoelectric thin-film multilayer body includes a substrate, an adhesive layer on the substrate, a lower electrode layer on the adhesive layer, and a lead-free piezoelectric thin-film layer on the lower electrode layer. The lead-free piezoelectric thin-film layer is composed of lithium potassium sodium niobate (composition formula (NaxKyLiz)NbO3, 0<x<1, 0<y<1, 0≦z≦1, x+y+z=1). The maximum height Rz of a roughness of an adhesive-layer-facing surface of the substrate is 2 nm or less. The adhesive layer is composed of a non-crystalline oxide of a Group 4 element or a non-crystalline oxide of a Group 5 element. The adhesive layer has a thickness of 1 nm or more and 2 nm or less and is equal to or more than the maximum height Rz of the roughness of the surface of the substrate.