Piezoelectric Ceramic Composition for High Curie Point Actuator
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Solution Overview
Problem
Piezoelectric ceramic compositions with insufficient Curie points and high dielectric constants impair piezoelectric properties when used in high electric field applications, leading to heat generation and reduced distortion capabilities, especially when co-fired with internal electrodes.
Innovation Solution
A piezoelectric ceramic composition with the formula (Pb(a-b)Me){(Ni(1-c)/3Znc/3Nb2d/3)zTixZr(1-x-z)}O3, where Me represents Ba, Sr, or Ca, and specific molar ratios of a, b, d, x, c, and z are adjusted to achieve a large piezoelectric constant, small dielectric constant, and high Curie point, preventing reduction in piezoelectric constant even when co-fired with internal electrodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the dielectric constant of piezoelectric material is increased to achieve large distortion, then the piezoelectric constant increases, but the heat generation increases and piezoelectric properties are impaired at high temperatures
Solution Approach 1:
The patent changes the chemical composition parameters of the piezoelectric material by introducing specific dopants (Nb at B-site, and Sr/Ba/Ca at A-site) to achieve the optimal balance between piezoelectric constant and dielectric constant, thereby controlling heat generation while maintaining large distortion capability
Solution Approach 2:
The patent creates a composite piezoelectric ceramic system by combining PZT base material with multiple dopants (Nb, Sr, Ba, Ca) to achieve synergistic effects that simultaneously improve piezoelectric properties while controlling dielectric constant and heat generation
2Temperature
If the Curie point is increased to enable continuous operation at high temperatures, then thermal stability improves, but piezoelectric constant may be reduced
Solution Approach 1:
The patent optimizes the compositional parameters within the PZT-Nb-Sr-Ba-Ca system to position the Curie point at an optimal value that enables continuous operation while preserving large piezoelectric constant, achieving simultaneous improvement in both thermal stability and piezoelectric performance
3Reliability
If Pb content is adjusted to achieve high Curie point and large piezoelectric constant, then piezoelectric properties improve, but manufacturing precision becomes difficult to control
Solution Approach 1:
The patent uses a multi-component composite system where multiple dopants work together to achieve the desired properties, providing more degrees of freedom for composition optimization and better control over manufacturing variability
Solution Approach 2:
The patent establishes specific compositional ranges and ratios for multiple dopants that create a robust formulation less sensitive to small variations in manufacturing, thereby improving precision control while maintaining excellent piezoelectric properties
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 piezoelectric constant of 550 pm/V or more, a dielectric constant of 3000 or less, and a Curie point of 280° C. or more, ensuring stable piezoelectric properties and reduced heat generation, making it suitable for high electric field operations without impairment.
Implementation Method 1
Piezoelectric ceramic compositions principally containing lead zirconate titanate (Pb(Ti, Zr)O3, hereinafter referred to as 'PZT') have excellent piezoelectric properties and therefore are widely used for piezoelectric devices such as piezoelectric actuators
Implementation Method 2
An increase in the dielectric constant of a piezoelectric material increases the amount of heat generated from a device made thereof. This is because the increase of the dielectric constant leads to an increase in capacitance to cause an increase in current
Data Source
AI summary
A piezoelectric ceramic composition has the composition formula (Pb(a-b)Meb){(Ni(1-c)/3Znc/3Nb2d/3)zTixZr(1-x-z)}O3, wherein Me represents at least one element selected from the group consisting of Ba, Sr and Ca; a, b, d, and x satisfy the inequalities 0.975≦a≦0.998, 0≦b≦0.05, 1<d≦1.3, and 0.39≦x≦0.47; and c and z are located in a region surrounded by lines connecting Point A (z=0.25, c=0.1), Point B (z=0.25, c=0.85), Point C (z=0.1, c=0.6), Point D (z=0.075, c=0.5), Point E (z=0.05, c=0.2), and Point F (z=0.05, c=0.1) or located on the lines in the z-c plane. Therefore, the piezoelectric ceramic composition is effective in achieving a large piezoelectric constant, a small dielectric constant, and a high Curie point. A piezoelectric actuator contains the piezoelectric ceramic composition.