Piezoceramic Material Composition for Knock Sensor Stability
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Solution Overview
Problem
Conventional piezoceramic materials used in piezoelectric sensors face challenges with temperature stability and sensitivity variations due to thermal expansion differences and pyroelectric effects, limiting their application in severe environments like automotive engines, where they are exposed to a wide temperature range.
Innovation Solution
A Pb/Zr/Ti/Sn/Sb/Nb oxide material with specific composition and crystallite size control, within the ranges of 1.000 ≤ m ≤ 1.075, 0.470 ≤ x < 0.490, 0.020 ≤ y ≤ 0.040, 0 < n < 1.000, and 0 < z ≤ 0.025, achieving a piezoelectric constant d33 of 340 pC/N or larger and a Curie temperature of 340°C or higher, enhancing both piezoelectric and temperature characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If conventional piezoceramic materials are used in piezoelectric sensors, then the sensors can operate within a limited temperature range (-40°C to 170°C), but the sensitivity varies and deteriorates when exposed to wider temperature ranges due to thermal expansion differences and pyroelectric effects
Solution Approach 1:
The patent modifies the piezoceramic material composition by adding specific dopants (Sn: 0.01-0.05 mol%, Nb: 0.01-0.05 mol%, Sb: 0.01-0.05 mol%) to PZT base material, changing the material parameters to achieve both wide temperature range operation and stable sensitivity. The dopants adjust the thermal expansion coefficient and suppress pyroelectric effects while maintaining piezoelectric properties.
Solution Approach 2:
The patent creates a composite piezoceramic material system by combining PZT (lead zirconate titanate) with multiple dopant elements (Sn, Nb, Sb). This composite approach allows the base PZT material to provide strong piezoelectric effect while the dopants contribute thermal stability and reduced temperature sensitivity variations.
2Measurement precision
If the piezoelectric sensor is designed for high sensitivity (high d33 constant), then the sensor output is enhanced, but the material requires precise composition control to maintain both high piezoelectric constant and high Curie temperature
Solution Approach 1:
The patent achieves high piezoelectric sensitivity (d33 ≥ 340 pC/N) and high Curie temperature (≥ 340°C) by precisely controlling multiple composition parameters within specific ranges. The systematic parameter optimization of dopant concentrations (Sn: 0.01-0.05 mol%, Nb: 0.01-0.05 mol%, Sb: 0.01-0.05 mol%) creates a robust material system that maintains high performance without requiring extreme precision.
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 provides improved piezoelectric sensitivity and heat resistance, reducing sensitivity variations and maintaining performance across a broader temperature range, making it suitable for high-temperature applications such as automotive engines.
Implementation Method 1
Each of the piezoelectric sensors includes a piezoelectric element equipped with a sintered piezoceramic body (bulk) and at least one pair of element electrodes so as to convert a mechanical stress applied thereto to an electricity or voltage by the piezoelectric effect of the piezoceramic body
Implementation Method 2
There also occurs a voltage in the piezoelectric sensor by the pyroelectric effect of the piezoceramic body in response to the temperature change
Data Source
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AI summary
A piezoceramic material according to an embodiment of the present invention has a composition represented by Pbn{Zr1-x-y-zTixSny(Sb1-nNbn)z}O3 where 1.000 ≤ m ≤ 1.075, 0.470 ≤ x < 0.490, 0.020 ≤ y ≤ 0.040, 0 < n < 1.000 and 0 < z ≤ 0.025 and a crystallite size of 30 to 39 nm.