Piezoelectric Substrate Phase Control via Thermal and Electric Fields
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Solution Overview
Problem
Existing piezoelectric materials, such as relaxor-PT crystals, exhibit unstable equilibrium states and limited control over crystal structure phases, which affects their electrical, mechanical, and optical properties, hindering their performance in ultrasonic and actuation applications.
Innovation Solution
A method is developed to form regions with varying crystal structures in a piezoelectric substrate by heating it above a transition temperature, rapidly cooling it, and applying an electric field to induce phase transitions, allowing for the creation of substrates with multiple crystal phases and corresponding property variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a single crystal structure phase is present in the material at room temperature, then the material exhibits stable equilibrium state, but the material experiences limited control over crystal structure phases and their properties
Solution Approach 1:
The patent applies dynamic control by using time-dependent cooling rates to transition the material from a stable single-phase state to a controllable multi-phase state. By varying the cooling rate after heating above the transition temperature, the system dynamically adjusts the crystal structure phases present at room temperature, enabling control over electrical, mechanical, and optical properties while maintaining compositional stability.
Solution Approach 2:
The patent changes physical parameters (temperature and cooling rate) to control crystal structure phases. By heating above the transition temperature and then applying different cooling rates, the system transforms the material from a stable single-phase equilibrium state to a controllable multi-phase state, achieving adaptability in material properties without compromising overall stability.
2Adaptability or versatility
If the crystal structure transitions between several different possible phases with very little compositional change, then the material exhibits vastly different electrical, mechanical, piezoelectric, pyroelectric and optical properties, but the material experiences relatively unstable equilibrium states
Solution Approach 1:
The patent applies preliminary action by heating the material above the transition temperature before cooling to establish a controlled phase transition. This preliminary heating ensures that the material is in a high-temperature phase where all crystal structures are accessible, and subsequent cooling at controlled rates determines the final phase composition, enabling reliable control over properties despite the inherent instability of equilibrium states.
Solution Approach 2:
The patent directly utilizes phase transitions as the core mechanism to achieve property control. By controlling the cooling rate through the transition temperature range, the system exploits the phase transition phenomenon to lock in different crystal structure phases at room temperature, transforming the instability of equilibrium states into a controllable feature that enables vast property variations.
3Manufacturing precision
If rapid cooling is applied to preserve a high-temperature crystal structure at room temperature, then the desired crystal structure persists, but the process requires precise control of cooling rate and temperature
Solution Approach 1:
The patent uses phase transitions as a controlled process to achieve precise crystal structure outcomes. By defining specific heating temperatures above the transition point and subsequent cooling rate ranges, the method creates a reproducible pathway from high-temperature phase to room-temperature phase, managing the complexity through standardized thermal processing parameters.
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
This technique enables the manipulation of crystal structures to improve the performance of piezoelectric devices by altering mechanical, electrical, and optical properties, enhancing directivity and frequency response, and allowing for the creation of smaller, more efficient arrays and transducers.
Implementation Method 1
a phase transition to a first crystal structure occurs when the piezoelectric substrate is heated above a transition temperature
Implementation Method 2
rapidly cooling the piezoelectric substrate below the transition temperature at a cooling rate that is sufficiently high for the first crystal structure to persist
Implementation Method 3
applying an electric field through one or more selected regions of the piezoelectric substrate, such that within the one or more selected regions, a second phase transition occurs and results in a second crystal structure
Implementation Method 4
relaxor-PT crystals exhibit an electromechanical coupling close to the theoretical maximum (k33>0.9) and piezoelectric voltage-strain coefficients up to a factor of five higher than traditional PZT ceramics
Data Source
AI summary
Among other things, piezoelectric materials and methods of their manufacture are described; particularly methods of forming regions of varying crystal structure within a relaxor piezoelectric substrate. Such methods may including heating the piezoelectric substrate above the transition temperature and below the Curie temperature such that a first phase transition occurs to a first crystal structure; rapidly cooling the piezoelectric substrate below the transition temperature at a cooling rate that is sufficiently high for the first crystal structure to persist; and applying an electric field through one or more selected regions of the piezoelectric substrate, such that within the one or more selected regions, a second phase transition occurs and results in a second crystal structure.