Pb-Free Piezoelectric Ceramic for High-Power Stability
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Solution Overview
Problem
Piezoelectric ceramics used in various applications require stable temperature characteristics and the ability to support high-power driving, especially in environments like supersonic motors and transducers, but existing Pb-based ceramics are harmful and Pb-free alternatives face challenges in temperature stability and high-power driving capabilities.
Innovation Solution
A Pb-free piezoelectric ceramic with a polycrystalline tungsten bronze structure, expressed by the composition formula 100[(Sr2-xCa x ) 1+y/4 Na 1-y Nb 5-2/5z Mn z O 15-2z ] + αSiO 2 , with a degree of axis c orientation of 60% or more, average crystal grain size between 3 µm and 5 µm, and no impurity phases, ensuring stable temperature characteristics and high-power driving capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Pb-based piezoelectric ceramics (PZT, PLZT) are used to achieve high-performance piezoelectric properties, then piezoelectric performance is improved, but harmful effects to human body increase
Solution Approach 1:
The invention changes the chemical composition parameters by replacing Pb with Sr and Ca, and adjusting the ratios of Na and Nb to achieve optimal piezoelectric performance without Pb. The specific composition range (0 ≤ x ≤ 2, 0 < y ≤ 1, 0 < z ≤ 0.5) represents parameter optimization to resolve the contradiction between performance and safety
Solution Approach 2:
The invention creates a composite material system combining Sr, Ca, Na, Nb, and Mn elements in a tungsten bronze structure, achieving high piezoelectric performance through synergistic effects of multiple elements while eliminating harmful Pb
2Object-affected harmful factors
If Pb-free piezoelectric ceramics are used to eliminate harmful effects, then safety is improved, but temperature characteristics and high-power driving capabilities deteriorate
Solution Approach 1:
The invention optimizes composition parameters (x, y, z ranges) and processing parameters (sintering temperature 1200-1400°C, cooling rate 5-50°C/h) to achieve both Pb-free formulation and excellent temperature characteristics with piezoelectric constant change rate of 40% or less from 25°C to 150°C
Solution Approach 2:
The invention introduces Mn at specific sites (z parameter) to locally enhance piezoelectric properties and temperature stability, while Sr and Ca substitution (x parameter) provides overall structural stability and high-power driving capability
3Reliability
If crystal grain size is increased to improve piezoelectric properties, then piezoelectric performance is improved, but mechanical quality coefficient and temperature stability deteriorate
Solution Approach 1:
The invention precisely controls crystal grain size within the 3-5 µm range through optimized sintering parameters (temperature 1200-1400°C, time 2-12 hours, cooling rate 5-50°C/h), achieving balance between piezoelectric performance and temperature stability
4Reliability
If degree of axis c orientation is increased to improve piezoelectric constants, then piezoelectric performance is improved, but manufacturing complexity increases
Solution Approach 1:
The invention achieves 60% or more axis c orientation by optimizing molding pressure (50-200 MPa) and sintering conditions, balancing piezoelectric performance with manufacturability through practical parameter ranges
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 ceramic exhibits a rate of change of 40% or less in piezoelectric constants and electro-mechanical coefficients across a wide temperature range, supports vibration speeds up to 1.6 m/s with minimal temperature rise and resonance frequency variation, and maintains high mechanical quality coefficients, enabling efficient and stable high-power driving.
Implementation Method 1
Piezoelectric elements are used as sensor elements and electricity generating elements, among others, by applying the piezoelectric effect of converting mechanical energy to electrical energy
Implementation Method 2
Piezoelectric elements are also used as vibrators, sound generators, actuators, supersonic motors, etc., that apply the reverse-piezoelectric effect of converting electrical energy to mechanical energy
Data Source
Figure 1(a)~1(b)
Figure 2
Figure 3(a)~3(c)
AI summary
A piezoelectric ceramic is expressed by the composition formula 100[(Sr2-xCax)1+y/4Na1-yNb5-2/5z MnzO15]+αSiO2 (in the formula, 0 ≤ x < 0.3, 0.1 < y < 0.6, 0 < z < 0.1 and 1 < α < 8) and constituted by polycrystal of tungsten bronze structure, wherein the degree of orientation of axis c of the polycrystal is 60% or more in Lotgering factor. The piezoelectric ceramic offers excellent temperature characteristics and supporting high-power driving.