Process for annealing a poled ceramic
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Solution Overview
Problem
Conventional heating protocols for poled ceramics result in poor high-temperature characteristics, limiting their performance and durability, particularly in applications requiring operation above 200-250°C.
Innovation Solution
A process involving incremental heating and controlled cooling of poled ceramics with a perovskite structure, allowing for the 'locking-in' of desirable high-temperature characteristics such as a high Curie point (Tc) and depolarizing temperature (Td), achieved by incremental temperature increases and dwell times at specific temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional heating protocol is used for annealing poled ceramic, then the process is simple and quick, but the high-temperature characteristics are poor
Solution Approach 1:
The annealing process is segmented into multiple temperature stages with specific dwell times. The process includes: heating to 380°C and holding for 4 hours, then heating to 580°C and holding for 16 hours, then heating to 680°C and holding for 4 hours, finally cooling to ambient temperature. This segmentation allows each temperature zone to contribute to different aspects of high-temperature performance, resolving the contradiction between process simplicity and reliability.
Solution Approach 2:
The patent applies preliminary action by performing incremental heating and dwelling at intermediate temperatures before reaching the final temperature. The staged approach with dwell periods at 380°C, 580°C, and 680°C allows the ceramic structure to progressively adapt and lock in desirable characteristics, transforming poor high-temperature performance into good performance through preparatory thermal treatment.
2Reliability
If incremental heating is applied over high temperature range, then high Curie point and depolarizing temperature are achieved, but the annealing time increases
Solution Approach 1:
The patent changes the temperature parameter dynamically during the annealing process. Instead of a single temperature, the process progresses through specific temperature points (380°C, 580°C, 680°C) with controlled dwell times. This parameter change strategy achieves high Curie point (650°C or more) and depolarizing temperature (580°C or more) while managing the total time through optimized heating rates and dwelling periods.
3Temperature
If high Tc materials are used, then operating temperature is improved, but piezoelectric activity (d33) decreases
Solution Approach 1:
The patent exploits phase transitions in the perovskite ceramic structure during the annealing process. By controlling heating through specific temperature ranges (380°C to 680°C), the process manages phase changes that lock in both high Curie point and high piezoelectric activity. The incremental heating allows the crystal structure to transition through phases that simultaneously provide high-temperature stability and strong piezoelectric response, resolving the typical trade-off between Tc and d33.
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 process enhances the ceramics' performance by achieving a low field piezoelectric activity (d33) of 50 or more, a Curie point (Tc) of 650°C or more, and a depolarizing temperature (Td) coincident with Tc, ensuring stability and effectiveness in high-temperature environments.
Implementation Method 1
heating the poled ceramic over a heating period from ambient temperature to a final temperature
Implementation Method 2
cooling the poled ceramic from the final temperature to ambient temperature
Implementation Method 3
judicious incremental heating of a poled ceramic over a high temperature range can serve to 'lock-in' desirable high temperature characteristics
Implementation Method 4
Piezoelectric materials generate an electric field in response to applied mechanical strain
Data Source
AI summary
The present invention relates to a process for annealing a poled ceramic over a heating period during which the temperature is raised incrementally to “lock-in” desirable high temperature characteristics.