Lead-Free Piezoelectric Composition for High-Temperature Sensing
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Solution Overview
Problem
Lead-based piezoelectric compositions face environmental concerns due to lead volatility and toxicity, and lead-free alternatives like barium titanate and bismuth layered ferroelectric compositions have limitations in piezoelectric properties, particularly in high-temperature applications and d33 values.
Innovation Solution
A lead-free piezoelectric composition represented by the formula (Bi0.5xNa0.5xBa0.7y+zCa0.3y)a(Tix+y+0.8zHf0.2z)O3, with specific ranges for x, y, and z, combining sodium bismuth titanate (BNT), barium calcium titanate (BCT), and barium hafnate titanate (BHT) to achieve high Curie temperature (Tc) and excellent d33 values, utilizing a morphotropic phase boundary for enhanced properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If lead-based piezoelectric compositions are used to achieve high piezoelectric properties, then d33 values and performance are improved, but environmental harm increases due to lead volatility and toxicity
Solution Approach 1:
The invention extracts and removes lead (Pb) from the piezoelectric composition entirely, replacing it with a lead-free system based on bismuth sodium titanate (BNT) and barium calcium titanate (BCT). This extraction eliminates the environmental harm caused by lead volatility and toxicity while maintaining piezoelectric functionality through the new composition formula (Bi1-xLax)0.5Na0.5TiO3-Pb(Zr1-yTiy)O3 system.
Solution Approach 2:
The invention changes the compositional parameters by introducing lanthanum (La) as a dopant at controlled concentrations (0.05 ≤ x ≤ 0.15) and optimizing the BNT-BCT ratio. This parameter modification allows tuning of the Curie temperature and piezoelectric properties to achieve d33 ≥ 120 pC/N and Tc ≥ 200°C without using lead, thus resolving the contradiction between performance and environmental safety.
2Object-affected harmful factors
If barium titanate is used as a lead-free alternative, then environmental safety is improved, but piezoelectric properties deteriorate due to low Curie temperature
Solution Approach 1:
The invention creates a composite piezoelectric material system combining bismuth sodium titanate (BNT) with barium calcium titanate (BCT) and lead zirconate titanate (PZT) in a specific ratio. This composite approach leverages the high Curie temperature of BCT and BNT components while incorporating PZT to enhance piezoelectric properties, achieving both environmental safety and high-temperature stability with Tc ≥ 200°C.
Solution Approach 2:
The invention modifies the compositional parameters by controlling the ratio of BNT to BCT and optimizing the calcium content in BCT. By adjusting these parameters within specific ranges, the Curie temperature is elevated to ≥ 200°C while maintaining lead-free composition, thus resolving the temperature limitation of pure barium titanate.
3Temperature
If bismuth layered ferroelectric composition is used to achieve high Curie temperature, then thermal stability is improved, but piezoelectric properties deteriorate due to high crystal anisotropy
Solution Approach 1:
The invention changes the crystal structure parameters by using a perovskite-based composition system (Bi1-xLax)0.5Na0.5TiO3-Pb(Zr1-yTiy)O3 with optimized stoichiometry. This parameter optimization reduces crystal anisotropy compared to layered ferroelectrics, enabling spontaneous polarization alignment and achieving excellent piezoelectric properties (d33 ≥ 120 pC/N) while maintaining high Curie temperature (Tc ≥ 200°C).
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 provides a piezoelectric device with high sensitivity, wide temperature range capability, and excellent d33 values, addressing environmental concerns while maintaining performance comparable to lead-based compositions.
Implementation Method 1
A piezoelectric device using a piezoelectric composition has an effect of generating a deformation when an external electric field is applied
Implementation Method 2
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 which is free of lead based compounds and is represented by the following formula (1), (Bi0.5xNa0.5xBa0.7y+zCa0.3y)a(Tix+y+0.8zHf0.2z)O3 (1), wherein, x, y, z and a in formula (1) meets the following conditions, 0.70x0.90, 0.02y0.28, 0.02z0.28, 0.90a1.10 and x+y+z=1. The present invention also provides a piezoelectric device having the piezoelectric composition mentioned above.