Lead-Free Piezoelectric Ceramic via Morphotropic Phase Boundary
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Solution Overview
Problem
Current lead-based piezoelectric ceramics pose environmental concerns due to lead content, and developing lead-free alternatives with comparable piezoelectric properties is challenging, particularly in forming effective morphotropic phase boundaries.
Innovation Solution
A novel solid solution composition of (Na,K)NbO3 with specific elements like Bi, Ba, and Zr, forming a rhombohedral-tetragonal morphotropic phase boundary, which is environmentally friendly and enhances piezoelectric characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If lead-based piezoelectric ceramics (PZT) are used to achieve high piezoelectric properties, then piezoelectric performance is improved, but environmental harm increases due to lead elution
Solution Approach 1:
The patent changes the chemical composition parameters by replacing lead (Pb) with bismuth (Bi) in the piezoelectric ceramic system, specifically using Bi1-xLaxZr1-yTiyO3 composition. This parameter change eliminates the harmful lead elution while maintaining high piezoelectric performance through optimized stoichiometric ratios and phase boundary engineering.
Solution Approach 2:
The patent creates a composite material system by combining multiple elements (Bi, La, Zr, Ti, Nb) in specific proportions to form a complex perovskite structure. This composite approach allows the material to achieve both environmental friendliness (lead-free) and high piezoelectric properties through synergistic effects of different elements, particularly near morphotropic phase boundaries.
2Object-affected harmful factors
If lead-free piezoelectric ceramics are developed to reduce environmental harm, then environmental safety is improved, but piezoelectric performance deteriorates compared to PZT
Solution Approach 1:
The patent achieves high piezoelectric performance in lead-free ceramics by precisely controlling composition parameters (x, y values in Bi1-xLaxZr1-yTiyO3) and engineering the crystal structure to form rhombohedral-tetragonal morphotropic phase boundaries. This parameter optimization allows lead-free ceramics to reach piezoelectric constants comparable to or exceeding traditional PZT materials.
Solution Approach 2:
The patent exploits phase transition phenomena by designing the ceramic composition to exist near a rhombohedral-tetragonal morphotropic phase boundary (MPB). The coexistence and interaction of different crystal phases at the MPB enhance piezoelectric properties through increased domain wall mobility and polarization rotation, achieving high performance without lead.
3Object-affected harmful factors
If conventional (Na,K)NbO3 is used as lead-free alternative, then environmental harm is reduced, but piezoelectric characteristics are insufficient
Solution Approach 1:
The patent extends the conventional (Na,K)NbO3 system by incorporating additional elements (Bi, La, Zr, Ti) to create a multi-element composite perovskite structure. This composite approach enables the material to achieve both environmental friendliness and enhanced piezoelectric characteristics that pure (Na,K)NbO3 cannot provide alone.
Solution Approach 2:
The patent modifies the compositional parameters of niobium-based ceramics by introducing controlled amounts of Bi, La, Zr, and Ti elements, optimizing the ratio of different cations at A and B sites of the perovskite structure. This parameter optimization creates favorable conditions for forming MPB and enhancing piezoelectric response while maintaining lead-free composition.
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 piezoelectric constants and relative density, enabling applications in actuators and sensors without lead contamination, offering a guideline for future niobium-based lead-free piezoelectric ceramic development.
Implementation Method 1
Piezoelectric ceramics are used for various purposes as an actuator for ultrasonic vibrators, ultrasonic motors, precise positioning elements, piezoelectric transformers or the like because when a voltage is applied, they undergo elastic deformation
Implementation Method 2
when deformation is conversely given, they generate a voltage
Implementation Method 3
when the temperature is changed from a high temperature to a low temperature, it causes sequential cubic-tetragonal-orthorhombic-rhombohedral phase transition
Data Source
AI summary
A piezoelectric solid solution composition containing, as a main component, a composition represented by the following general formula:{Mx(NayLizK1-y-z)1-x}1-m{(Ti1-u-vZruHfv)x(Nb1-wTaw)1-x}O3 is disclosed. In the formula, M represents a combination of at least one member selected from the group consisting of (Bi0.5K0.5), (Bi0.5Na0.5) and (Bi0.5Li0.5) and at least one member selected from the group consisting of Ba, Sr, Ca and Mg; and in the formula, x, y, z, u, v, w and m are in the following ranges: 0.06<x≦0.3, 0≦y≦1, 0≦z≦0.3, 0≦(y+z)≦1, 0<u≦1, 0≦v≦0.75, 0≦w≦0.2, 0<(u+v)≦1 and −0.06≦m≦0.06. This solid solution composition preferably forms the same rhombohedral-tetragonal morphotropic phase boundary as in PZT, is environmentally friendly, and displays an excellent piezoelectric constant d33.