Lead-Free Piezoelectric Composite Oxide for High-Temperature Stability
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Solution Overview
Problem
Lead-based piezoelectric materials, such as PZT, pose environmental concerns, and lead-free alternatives like Bi(Zn0.5, Ti0.5)O3 face difficulties in poling procedures and exhibit poor high-temperature stability, limiting their application in devices that operate at elevated temperatures.
Innovation Solution
A novel lead-free piezoelectric material with a perovskite-type composite oxide structure, represented by the formula ABO3-yA′BO3-zA″B′O3, where A is Bi, A′ is a rare earth element, and B′ includes elements like Ti, Zn, and Sn, forming a morphotropic phase boundary with BaTiO3, allowing for easier sintering and improved piezoelectric characteristics at high temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If lead-free perovskite-type oxides like Bi(Zn0.5, Ti0.5)O3 are used to replace lead-based PZT, then environmental harm is reduced, but poling procedure becomes difficult and piezoelectric characteristics cannot be exhibited
Solution Approach 1:
The invention changes the compositional parameters by introducing a third component A''B''O3 (such as BaTiO3, SrTiO3, CaZrO3) to form a ternary composite system. This compositional modification reduces the c/a ratio anisotropy and lowers the Curie temperature, thereby enabling successful poling procedure while maintaining lead-free environmental benefits
Solution Approach 2:
The invention creates a composite piezoelectric material by combining three perovskite-type oxide components: ABO3 (Bi-based), A'B'O3 (rare earth-based), and A''B''O3 (alkaline earth-based). This composite structure synergistically improves polability and piezoelectric characteristics while eliminating lead content
2Reliability
If (Bi0.5, Na0.5)TiO3 is used to achieve excellent piezoelectric characteristics at room temperature, then piezoelectric performance is improved, but high-temperature stability deteriorates with abrupt degradation at 150°C or more
Solution Approach 1:
The invention adjusts the compositional parameters by incorporating A''B''O3 components (BaTiO3, SrTiO3, CaZrO3) which have high Curie temperatures, thereby raising the overall Curie temperature of the composite material to above 150°C and enabling stable operation at elevated temperatures while maintaining room-temperature piezoelectric performance
3Temperature
If Bi(Zn0.5, Ti0.5)O3 is used to achieve high Curie temperature, then temperature stability is improved, but poling procedure becomes difficult due to high anisotropy (c/a=1.21)
Solution Approach 1:
The invention modifies the crystallographic parameters by introducing A''B''O3 components that reduce the c/a ratio from 1.21 to below 1.08. This parameter change reduces the anisotropy and enables easier domain alignment during poling while maintaining a Curie temperature above 150°C
Solution Approach 2:
The A''B''O3 component acts as an intermediary that mediates between the high Curie temperature requirement and the poling ease requirement. It provides a compositional buffer that reduces anisotropy without significantly lowering the Curie temperature, facilitating successful poling procedure
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 material achieves excellent piezoelectric properties and high Curie temperature stability, overcoming the poling difficulties and environmental concerns of lead-based materials, while maintaining durability and performance in high-temperature devices.
Implementation Method 1
The present invention relates to a piezoelectric material and in particular to a novel lead-free piezoelectric material having a high Curie temperature
Implementation Method 2
a novel lead-free piezoelectric material having a high Curie temperature
Data Source
AI summary
Provided is a piezoelectric material including a lead-free perovskite-type composite oxide which is excellent in piezoelectric characteristics and temperature characteristics and is represented by the general formula (1):xABO3-yA′BO3-zA″B′O3 in which A is a Bi element; A′ is a rare earth element including La; B is at least one element selected from Ti, Zn, Sn and Zr; A″ is at least one element selected from Ba, Sr and Ca; B′ is at least one element selected from divalent, trivalent, pentavalent, tetravalent, and hexavalent elements; and x is a value of 0.10 or more and 0.95 or less, y is a value of 0 or more and 0.5 or less, and z is a value of 0 or more and 0.7 or less, provided that x+y+z=1.