Lead-Free Piezoelectric Ceramic Composition for Stable Room Temperature Performance
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Solution Overview
Problem
The KNbO3 - NaNbO3 piezoelectric ceramic composition has a low piezoelectric constant and undergoes a second-order phase transition near room temperature, limiting its practical applications.
Innovation Solution
A piezoelectric ceramic composition represented by the formula (1-y-z-w)(K x Na 1-x )NbO3 + yLiNbO3 + zSrTiO3 + wBiFeO3, with specific ranges for x, y, z, and w to enhance the piezoelectric constant and prevent second-order phase transitions near room temperature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If KNbO3-NaNbO3 piezoelectric ceramic composition is used as a lead-free alternative, then environmental harm is reduced, but the piezoelectric constant remains low
Solution Approach 1:
The patent uses a composite material system combining KNbO3, NaNbO3, LiNbO3, SrTiO3, and BiFeO3 to achieve both lead-free composition and high piezoelectric performance. The synergistic interaction between multiple components allows the material to overcome the limitations of individual compounds, achieving d33 > 150 pC/N while maintaining environmental compatibility.
Solution Approach 2:
The patent systematically varies compositional parameters (molar ratios of different components) to optimize performance. By adjusting the proportions of KNbO3, NaNbO3, LiNbO3, SrTiO3, and BiFeO3 within specific ranges, the piezoelectric constant is maximized while suppressing phase transitions, demonstrating parameter optimization to resolve the contradiction.
2Object-affected harmful factors
If KNbO3-NaNbO3 composition is used to eliminate lead, then environmental safety is improved, but second-order phase transition occurs near room temperature causing property degradation
Solution Approach 1:
The patent changes the compositional parameters by introducing LiNbO3, SrTiO3, and BiFeO3 components with specific molar ratios. This parameter modification shifts the phase transition temperature away from room temperature, stabilizing the material properties in the operational temperature range while maintaining the lead-free advantage.
Solution Approach 2:
The multi-component composite structure creates a more complex energy landscape that suppresses the second-order phase transition. The interaction between different crystal phases in the composite system stabilizes the ferroelectric phase at room temperature, preventing property degradation.
3Ease of manufacture
If simple KNbO3-NaNbO3 composition is used, then manufacturing complexity is reduced, but piezoelectric performance is insufficient for practical applications
Solution Approach 1:
The patent employs a five-component composite system (KNbO3, NaNbO3, LiNbO3, SrTiO3, BiFeO3) that achieves high piezoelectric performance (d33 > 150 pC/N). The composite structure allows each component to contribute specific properties, achieving superior performance that cannot be obtained with simpler compositions.
Solution Approach 2:
The patent optimizes manufacturing parameters including sintering temperature (900-1100°C), composition ratios, and processing conditions to facilitate the production of the multi-component composite. By controlling these parameters, the complex composition can be manufactured effectively while achieving the desired high piezoelectric constant.
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 a higher piezoelectric constant than conventional KNbO3 - NaNbO3 compositions and eliminates second-order phase transitions in the range of 10 °C to 40 °C, ensuring stable performance and improved sintering properties.
Implementation Method 1
a piezoelectric ceramic composition which exhibits a higher piezoelectric constant than conventionally known KNbO3 - NaNbO3 piezoelectric ceramic composition
Implementation Method 2
there exists the second order phase transition which is formed by a phase change from a ferroelectric phase at a lower temperature to a ferroelectric phase at a higher temperature
Data Source
Figure 1~2
Figure 3~4
AI summary
A KNbO3-NaNbO3 piezoelectric porcelain composition which exhibits a larger piezoelectric constant than those of conventional ones and does not have any secondary phase transition point in the neighborhood of room temperature (10 to 40°C), that is, a piezoelectric porcelain composition represented by the general formula: (1-y-z-w)(KxNa1-x)NbO3 + yLiNbO3 + zSrTiO3 + wBiFeO3, wherein (KxNa1-x)NbO3 represents potassium sodium niobate; LiNbO3 represents lithium niobate,; SrTiO3 represents strontium titanate; and BiFeO3 represents bismuth ferrate; with the proviso that 0.4 < x < 0.6, 0 < y ≤ 0.1, 0 < z < 0.1, 0 < w < 0.09, and 0.03 < y + z + w ≤ 0.12.