Lead-Free Piezoelectric Composition via Bismuth Sodium Titanate Composite
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Solution Overview
Problem
Lead-based piezoelectric compositions face environmental concerns due to high lead volatility, and existing lead-free alternatives like barium titanate and bismuth layered ferroelectric materials lack sufficient spontaneous polarization and piezoelectric displacement, making them impractical for applications like sensors and actuators.
Innovation Solution
A bismuth sodium titanate-based piezoelectric composition with a perovskite structure, characterized by the formula (Bi(0.5x+y+z)Na0.5x)m(Ti(x+0.5y)Mg0.5yMez)O3, where x, y, and z are within specific ranges, incorporating transition metal elements like Mn, Cr, Fe, or Co, to enhance spontaneous polarization and piezoelectric displacement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If lead-based piezoelectric compositions are used, then high piezoelectric performance is achieved, but environmental harm increases due to lead volatility
Solution Approach 1:
The invention changes the chemical composition parameters by replacing lead-based compounds with bismuth-based compounds (Bi0.5Na0.5TiO3 and Bi(Mg0.5Ti0.5)O3) in specific ratios, thereby eliminating lead volatility while maintaining piezoelectric performance through optimized compositional parameters
Solution Approach 2:
The invention uses a composite material system combining two bismuth-based perovskite phases (BNT and BMT) in a specific ratio range, creating a composite piezoelectric material that achieves high performance without lead, resolving the contradiction between performance and environmental harm
2Object-affected harmful factors
If barium titanate is used as lead-free alternative, then environmental friendliness is improved, but piezoelectric displacement becomes insufficient due to low curie point
Solution Approach 1:
The invention creates a composite of two bismuth-based perovskites (BNT-BMT system) that combines the environmental benefits of lead-free materials with enhanced piezoelectric properties, achieving both environmental friendliness and sufficient piezoelectric displacement
Solution Approach 2:
The invention optimizes the compositional parameters (ratio of BNT to BMT between 3:7 and 7:3) and structural parameters (tetragonality) to achieve high spontaneous polarization and piezoelectric displacement, overcoming the limitations of single-phase lead-free materials
3Stability of the object's composition
If bismuth layered ferroelectric is used, then thermal stability is improved, but manufacturing complexity increases due to high crystal anisotropy
Solution Approach 1:
The invention changes the crystal structure parameters by forming a perovskite-phase composite (而非layered structure) with optimized tetragonality, achieving thermal stability while avoiding the high crystal anisotropy that causes manufacturing complexity in bismuth layered ferroelectrics
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 composition achieves high spontaneous polarization and large piezoelectric displacement, enabling effective use in sensors and actuators while being environmentally friendly by minimizing 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. In the piezoelectric composition, the main component is represented by the following formula with a perovskite type structure,(Bi(0.5x+y+z)Na0.5x)m(Ti(x+0.5y)Mg0.5yMez)O3 wherein, 0.05≦x≦0.7, 0.01≦y≦0.7, 0.01≦z≦0.6, 0.75≦m≦1.0, x+y+z=1 and the transition metal element Me is any one or more selected from the group consisting of Mn, Cr, Fe and Co.