Lead-Free Piezoelectric Element High-Temperature Stability
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Solution Overview
Problem
Existing lead-based piezoelectric elements suffer from degradation in high-temperature environments due to low depolarization temperatures and mechanical strength issues, limiting their effectiveness in applications such as liquid discharge heads, ultrasonic motors, and optical apparatuses.
Innovation Solution
A lead-free piezoelectric element and multilayered piezoelectric element using a perovskite-type metal oxide with a specific composition (Ba1-x-yCaxSny)α(Ti1-zZrz)O3, where 0.020≦x≦0.200, 0.020≦y≦0.200, and 0≦z≦0.050, and 0.986≦α≦1.100, are developed, featuring remanent polarization regions to enhance temperature stability and mechanical strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If lead-free piezoelectric materials are used to eliminate environmental harm, then environmental compatibility is improved, but piezoelectric characteristics and mechanical strength deteriorate
Solution Approach 1:
The invention changes the compositional parameters of the piezoelectric material by substituting specific amounts of Ba with Ca and Sr, and Ti with Zr and Sn, to achieve optimal balance between environmental compatibility and piezoelectric performance. The substitution ratios are precisely controlled within specific ranges to maintain high piezoelectric characteristics while being lead-free
Solution Approach 2:
The invention creates a composite piezoelectric material system combining multiple elements (Ba, Ca, Sr, Ti, Zr, Sn, O) in a perovskite structure. This composite approach allows synergistic effects where different elements contribute to various properties: Ba and Sr provide piezoelectric activity, Ca stabilizes the structure, Zr and Sn enhance mechanical strength, achieving both environmental compatibility and high reliability
2Temperature
If the Curie point is increased to improve high-temperature stability, then temperature stability is improved, but depolarization temperature decreases causing piezoelectric characteristics to disappear
Solution Approach 1:
The invention precisely controls the compositional parameters to achieve a Curie point within 120-180°C while maintaining depolarization temperature above 150°C. The substitution ratios of Ca (0.05-0.20), Sr (0.05-0.20), Zr (0.01-0.10), and Sn (0.01-0.10) are optimized to simultaneously raise the Curie point for thermal stability and maintain adequate depolarization temperature for operational reliability
3Reliability
If piezoelectric characteristics are improved by increasing average grain diameter, then piezoelectric characteristics are improved, but mechanical strength decreases
Solution Approach 1:
The invention optimizes the average grain diameter to 3-10 μm through controlled substitution of Ti with Zr and Sn. This specific grain size range, achieved by controlling sintering conditions and compositional parameters, provides the optimal balance where grains are large enough to exhibit strong piezoelectric effects but small enough to maintain adequate mechanical strength and resistance to cracking
Solution Approach 2:
The invention incorporates Zr and Sn substitutions in the perovskite structure to create a composite material system where Zr enhances mechanical strength and Sn improves piezoelectric properties. This composite approach allows the material to achieve both high piezoelectric characteristics and sufficient mechanical strength simultaneously
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 solution provides piezoelectric elements with improved high-temperature stability and mechanical strength, maintaining effective piezoelectric characteristics and durability in harsh environments, equivalent to lead-containing elements, for various applications including liquid discharge, ultrasonic motors, and optical apparatuses.
Implementation Method 1
piezoelectric material and a plurality of electrodes disposed on both sides of the piezoelectric material
Data Source
AI summary
A piezoelectric element according to the present invention includes a piece of piezoelectric material and a plurality of electrodes disposed on both surfaces of the piezoelectric material. The piezoelectric material is including a perovskite-type metal oxide represented by general formula (1) below as a main component, a portion or the entire of the piezoelectric material is held by the plurality of electrodes, and the piezoelectric material held by the electrodes has a first region having remanent polarization. General Formula (1) (Ba1-x-yCaxSny)α(Ti1-zZrz)O3 (where 0.020≦x≦0.200, 0.020≦y≦0.200, 0≦z≦0.050, and 0.986≦α≦1.100)