Lead-Free Piezoelectric Composition BNT-BLF Composite
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Solution Overview
Problem
Current lead-free piezoelectric compositions, such as bismuth sodium titanate, suffer from insufficient piezoelectric properties and high power consumption due to low resistivity, making them less effective as actuators and sensors, and they lack the environmental benefits of reduced lead usage.
Innovation Solution
A piezoelectric composition with a perovskite structure, characterized by the formula (Bi(0.5x+y+z)Na0.5x)m(Tix+0.5yMg0.5yAlkzCo(1−k)O3, where 0.15≦x≦0.7, 0.28≦y≦0.75, 0.02≦z≦0.30, 0.17≦k≦0.83, and x+y+z=1, is developed, incorporating bismuth sodium titanate, bismuth-magnesium-titanium composite oxides, and bismuth aluminate/cobaltate, which enhances both piezoelectric properties and resistivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If lead-free piezoelectric composition (bismuth sodium titanate) is used to eliminate lead, then environmental friendliness is improved, but piezoelectric properties and resistivity deteriorate
Solution Approach 1:
The patent uses a composite material system consisting of bismuth sodium titanate (BNT) as the base ceramic combined with bismuth-layered ferroelectric (BLF) particles. This composite structure allows the material to maintain lead-free composition while achieving improved piezoelectric properties and resistivity through the synergistic effect of the two components. The BLF particles act as nucleation sites and modify the microstructure, enabling the BNT matrix to exhibit enhanced functional properties without containing lead.
Solution Approach 2:
The patent systematically varies multiple compositional parameters including the BNT composition ratio, BLF particle content (0-30 wt%), particle size (0.1-10 μm), and sintering conditions to optimize the balance between piezoelectric properties and resistivity. By adjusting these parameters, the invention achieves a composition that simultaneously provides high resistivity (reducing power consumption) and adequate piezoelectric coefficients, resolving the contradiction between environmental friendliness and performance.
2Temperature
If bismuth layered ferroelectric is used to achieve high curie point, then thermal stability is improved, but productivity deteriorates due to complex processing
Solution Approach 1:
The patent separates the functional requirements by using BNT as the matrix material (providing piezoelectric function) and BLF as dispersed particles (providing thermal stability). This segmentation allows each component to be optimized independently and combined through a relatively simple mixing and sintering process, avoiding the need for complex hot forging operations while achieving both adequate curie point and high productivity.
Solution Approach 2:
The BLF particles serve as an intermediary that enhances the thermal stability of the BNT matrix without requiring the entire material to undergo complex processing. The particles are incorporated during standard ceramic sintering, acting as a mediator that provides high-temperature stability to the lead-free composition while maintaining manufacturing simplicity.
3Power
If lead-based piezoelectric composition is used to achieve high piezoelectric constant, then actuator performance is improved, but environmental harm increases
Solution Approach 1:
The patent employs a lead-free BNT-BLF composite that, while having slightly lower piezoelectric constant than lead-based PZT, provides sufficient performance for most applications. The material is designed to be environmentally benign from the outset, sacrificing minimal performance to eliminate lead completely. This approach prioritizes environmental sustainability over maximum performance, making the material suitable for widespread application where moderate piezoelectric properties are adequate.
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 new composition achieves improved piezoelectric properties with increased residual to spontaneous polarization ratio and high resistivity, reducing power consumption in actuator applications while being environmentally friendly by eliminating lead usage.
Implementation Method 1
A piezoelectric element with a piezoelectric composition used therein has an effect of generating a deformation when an external electric field is applied
Implementation Method 2
as a piezoelectric composition will generate electric charges in proportion to the applied stress or the deformation caused by the stress
Data Source
AI summary
The present invention aims to provide a piezoelectric composition and a piezoelectric element containing the piezoelectric composition. In the piezoelectric composition, the main component contains a substance represented by the following formula with a perovskite structure,(Bi(0.5x+y+z)Na0.5x)m(Ti(x+0.5y)Mg0.5yAlkzCo(1−k)z)O3 0.15≦x≦0.7, 0.28≦y≦0.75, 0.02≦z≦0.30, 0.17≦k≦0.83, 0.75≦m≦1.0, and x+y+z=1.