Lead-Free Piezoelectric Composition via Transition Metal Substitution
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Solution Overview
Problem
Lead-based piezoelectric compositions pose environmental concerns due to high lead oxide volatility, and sodium bismuth titanate-based compositions have insufficient piezoelectric properties, making it difficult to achieve lead-free piezoelectric materials with good thermal stability and polarization.
Innovation Solution
A lead-free piezoelectric composition with a perovskite-type oxide structure, containing Bi, Na, and K at A-sites and Ti partly substituted with transition metals like Mn, Cr, Fe, or Co, which enhances electron localization and Coulomb interaction, allowing for rhombohedral or tetragonal perovskite structures with improved piezoelectric properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If lead-based piezoelectric compositions are used, then excellent piezoelectric properties are achieved, but environmental pollution and high lead oxide volatility occur
Solution Approach 1:
The patent changes the chemical composition parameters by substituting lead (Pb) with bismuth (Bi) and sodium (Na) in the perovskite structure, specifically using the formula (1-x-y)Na1/2Bi1/2TiO3-xBiMeO3-yBi0.5K0.5TiO3. This parameter change eliminates the harmful lead oxide volatility while maintaining piezoelectric functionality through the morphotropic phase boundary between rhombohedral and tetragonal phases.
Solution Approach 2:
The patent creates a composite piezoelectric material system combining multiple components: sodium bismuth titanate (Na1/2Bi1/2TiO3), bismuth transition metal oxide (BiMeO3), and bismuth potassium titanate (Bi0.5K0.5TiO3). This composite approach allows the material to achieve excellent piezoelectric properties comparable to lead-based PZT while being environmentally friendly and free from lead contamination.
2Object-affected harmful factors
If sodium bismuth titanate-based compositions are used to replace lead, then environmental friendliness is improved, but piezoelectric properties become insufficient
Solution Approach 1:
The patent optimizes the compositional parameters by precisely controlling the substitution amounts of transition metals (Mn, Cr, Fe, or Co) and potassium in the perovskite structure. The specific formula (1-x-y)Na1/2Bi1/2TiO3-xBiMeO3-yBi0.5K0.5TiO3 with controlled x and y values allows tuning of the crystal structure to achieve the morphotropic phase boundary, thereby maximizing piezoelectric properties in the lead-free system.
Solution Approach 2:
The patent develops a multi-component composite material system that combines sodium bismuth titanate with bismuth transition metal oxide and bismuth potassium titanate. This composite structure creates a morphotropic phase boundary between rhombohedral and tetragonal phases, which significantly enhances the piezoelectric response and makes the lead-free composition competitive with traditional lead-based materials.
3Stability of the object's composition
If bismuth layered ferroelectrics are used, then thermal stability is improved, but polarization becomes difficult due to high crystallographic anisotropy
Solution Approach 1:
The patent changes the crystal structure parameters by adopting a perovskite structure with controlled A-site and B-site element substitutions. The formula (1-x-y)Na1/2Bi1/2TiO3-xBiMeO3-yBi0.5K0.5TiO3 creates a morphotropic phase boundary that reduces crystallographic anisotropy compared to layered structures, enabling easier polarization through conventional electric field application while maintaining high Curie temperature and thermal stability.
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 suppresses segregation and heterogeneous structures, achieving excellent piezoelectric properties, including high spontaneous polarization, and is environmentally friendly, suitable for various applications without lead contamination.
Implementation Method 1
Piezoelectric compositions have the effect of inducing strain when electric fields are applied to the piezoelectric compositions from outside (the effect of converting electrical energy into mechanical energy)
Implementation Method 2
the effect of generating a charge on the surface when stresses are applied to the piezoelectric compositions from outside (the effect of converting mechanical energy into electrical energy)
Data Source
AI summary
Provided is a piezoelectric composition containing a major component that is a perovskite-type oxide which is represented by the general formula ABO3, which contains no Pb, and which has A-sites containing Bi, Na, and K and B-sites containing Ti. The Ti is partly substituted with a transition metal element Me that is at least one selected from the group consisting of Mn, Cr, Fe, and Co. The content of Bi and the transition metal element Me in the perovskite-type oxide, which is the major component, is 6 mole percent to 43 mole percent in terms of Biu1MeO3.