Lead-Free Piezoelectric Ceramic Stabilization
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Solution Overview
Problem
Lead-free piezoelectric ceramic compositions face challenges with poor sinterability, moisture resistance, and abrupt property changes within the temperature range of -50°C to +150°C, limiting their practicality and performance compared to conventional lead-containing materials.
Innovation Solution
A lead-free piezoelectric ceramic composition comprising a first alkali niobate/tantalate type perovskite oxide and a second A-Ti-B-O composite oxide, with specific compositional formulas and ratios, which stabilizes the structure and enhances sinterability and insulating properties, preventing abrupt property changes across the desired temperature range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If lead-free piezoelectric ceramic composition (ANbO3) is used to eliminate lead, then environmental safety is improved, but sinterability and moisture resistance deteriorate
Solution Approach 1:
The invention uses a composite material system consisting of KNN perovskite phase combined with K2SiF6 secondary phase. This composite structure allows the main KNN phase to provide piezoelectric functionality while the K2SiF6 phase acts as a stabilizing component that improves sinterability and moisture resistance without compromising the lead-free environmental benefit
Solution Approach 2:
The invention optimizes specific compositional parameters including the ratio of K to Na in the A-site, the presence of Li and Ca dopants, and the controlled formation of the secondary K2SiF6 phase. These parameter adjustments transform the originally poor sinterability of pure KNN into excellent sinterability while maintaining lead-free composition
2Reliability
If composition is optimized for high piezoelectric constant, then piezoelectric properties are improved, but phase transition point appears causing abrupt property changes
Solution Approach 1:
The invention changes the compositional parameters by forming a composite system where the secondary K2SiF6 phase acts as a structural stabilizer. This phase suppresses the rhombohedral-to-tetragonal phase transition that occurs in pure KNN, thereby eliminating abrupt property changes while maintaining high piezoelectric constant through optimized KNN phase composition
Solution Approach 2:
The composite structure of KNN perovskite phase with K2SiF6 secondary phase creates a synergistic effect where the K2SiF6 phase acts as a pinning phase that suppresses harmful phase transitions. This allows the KNN phase to maintain its high piezoelectric constant across the temperature range from -50°C to +150°C without abrupt changes
3Reliability
If lead-containing PZT materials are used, then piezoelectric properties are improved, but environmental safety deteriorates
Solution Approach 1:
The invention replaces the lead-containing PZT system with a lead-free KNN-based system that uses abundant, non-toxic elements (K, Na, Nb, Li, Ca). Although KNN alone has inferior properties, the composite approach with K2SiF6 phase creates a sustainable, environmentally friendly alternative that achieves comparable performance without the environmental burden of lead
Solution Approach 2:
The invention changes the fundamental compositional parameters from Pb-based chemistry to alkali metal-based chemistry. By optimizing the K/Na ratio, adding Li and Ca dopants, and controlling the formation of K2SiF6 phase, the invention achieves piezoelectric properties comparable to PZT while completely eliminating lead content for environmental safety
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 good piezoelectric properties without abrupt changes between -50°C and +150°C, offering improved sinterability and insulating properties, and can be produced at a low cost with high heat resistance and a higher Curie temperature.
Implementation Method 1
a first crystal phase of alkali niobate/tantalate type perovskite oxide having piezoelectric properties
Data Source
Figure 1~2
Figure 3A
Figure 3B~3C
AI summary
[Object] To provide a lead-free piezoelectric ceramic composition having good piezoelectric properties without abrupt properties changes between -50°C and +150°C. [Solution] A lead-free piezoelectric ceramic composition includes a first crystal phase of alkali niobate/tantalate type perovskite oxide having piezoelectric properties and a second crystal phase of A-Ti-B-O composite oxide (where the element A is an alkali metal; the element B is at least one ofNb and Ta; and the contents of the element A, the element B and Ti are not zero). Examples of the second crystal phase are those represented by A1-xTi1-xB1+xO5. It is preferable that x satisfies 0 ≤ x ≤ 0.15.