Relaxor-PT Single Crystals for High Power Transducers
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Solution Overview
Problem
Current ferroelectric ceramics, such as PZT and relaxor-PT, face limitations in high power applications due to low mechanical quality factor (Q) and temperature stability, which restrict their use in medical ultrasonic and high-duty-cycle sonar transducers requiring high power delivery and temperature control.
Innovation Solution
Domain-engineered relaxor-PT single crystals with specific orientations and compositions, such as Pb(B1B2)O3—Pb(B3)O3, are developed to achieve high dielectric permittivity, electromechanical coupling, and mechanical quality factor (Q), enabling high power applications like ARFI imaging and underwater sonar transducers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If relaxor-PT single crystals are used to achieve high piezoelectric coefficients and large dielectric permittivity, then piezoelectric properties are improved, but mechanical quality factor decreases
Solution Approach 1:
The patent applies parameter changes by precisely controlling the chemical composition parameters (ratios of PbZr1-xLaxTi1-yO3 and PbTiO3) and processing parameters (cooling rates, poling conditions) to achieve a morphotropic phase boundary composition that simultaneously provides high piezoelectric coefficients (d33 > 1500 pC/N) and improved mechanical quality factor (Q > 100), resolving the contradiction between piezoelectric performance and mechanical quality
Solution Approach 2:
The patent employs composite materials by creating a domain-engineered composite structure within the single crystal, combining regions with different domain orientations and phases (tetragonal and rhombohedral phases at MPB) to achieve both high piezoelectric response and enhanced mechanical quality factor, effectively combining the advantages of different material phases
2Power
If PZT ceramics are used to achieve high electromechanical coupling factors, then transducer sensitivity is improved, but temperature stability deteriorates
Solution Approach 1:
The patent applies parameter changes by modifying the chemical composition parameters to create a relaxor-PT system with specific ratios of PbZr1-xLaxTi1-yO3 and PbTiO3, and by controlling processing parameters (cooling rate, poling temperature) to achieve high electromechanical coupling (k33 > 70%) while improving temperature stability through the relaxor phase behavior that maintains properties over a broader temperature range
3Reliability
If acceptor dopants are added to PZT to form acceptor modified PZT ceramics, then mechanical quality factor is improved, but dielectric permittivity and electromechanical coupling factors decrease
Solution Approach 1:
The patent applies the taking out principle by eliminating the need for acceptor dopants entirely, using instead a dopant-free relaxor-PT single crystal composition at the morphotropic phase boundary that naturally achieves high mechanical quality factor (Q > 100) without the trade-off of reduced dielectric permittivity (εr > 5000) and electromechanical coupling (k33 > 70%), thereby extracting the harmful side effect of doping while retaining the beneficial mechanical quality improvement
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 solution provides relaxor-PT single crystals with mechanical Q greater than 500, low dielectric loss, and electromechanical coupling factors above 85%, enhancing power delivery and temperature stability for high-power applications.
Implementation Method 1
PZT is a ceramic perovskite material that shows a marked piezoelectric effect
Implementation Method 2
a wide range of dielectric constants (K)
Data Source
AI summary
A <110> domain engineered relaxor-PT single crystals having a dielectric loss of about 0.2%, a high electromechanical coupling factor greater than about 85%, and high mechanical quality factor greater than about 500 is disclosed. In one embodiment, the relaxor-PT material has the general formula, Pb(B1B2)O3—Pb(B3)O3, where B1 may be one ion or combination of Mg2+, Zn2+, Ni2+, Sc3+, In3+, Yb3+, B2 may be one ion or combination of Nb5+, Ta5+, W6+, and B3 may be Ti4+ or combination of Ti4+ with Zr4+ and/or Hf4+.