Piezoelectric Ceramic Orientation via Low-Temperature Firing
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Solution Overview
Problem
The manufacturing method for piezoelectric oriented ceramics containing a Pb(Ti, Zr)O3-based compound results in loss of crystal orientation during the sintering process due to mutual diffusion of Ti and Zr, preventing the achievement of high crystal orientation and sintered density.
Innovation Solution
The method involves preparing single crystal powders of Pb(Ti, Zr)O3, forming a slurry, orienting it in a magnetic field, and firing the compact at a temperature lower than the standard firing temperature for an extended period, ensuring a degree of orientation not lower than 0.64 and sintered density not lower than 85% of theoretical density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the compact is fired at a high temperature for a short time to achieve sufficient sintered density, then the sintered density reaches 85% or higher of theoretical density, but the crystal orientation is lost due to mutual diffusion of Ti and Zr
Solution Approach 1:
The patent applies preliminary action by conducting the magnetic field application step before the firing process to establish crystal orientation in advance. The slurry is formed in a magnetic field to align particles with desired orientation, and this oriented structure is preserved by using a low-temperature, long-duration firing regime rather than high-temperature short-time firing that would cause atomic diffusion and loss of orientation.
Solution Approach 2:
The patent changes the firing parameters from the conventional high temperature-short time regime to a low temperature-long duration regime. Specifically, the firing temperature is set to 900°C to 1100°C (lower than conventional temperatures) and the holding time is extended to 10 hours or more, which allows sufficient mass transfer for sintering while suppressing atomic diffusion that would disrupt crystal orientation.
2Manufacturing precision
If the firing temperature is reduced to maintain crystal orientation, then crystal orientation is preserved, but the sintered density may be insufficient
Solution Approach 1:
The magnetic field application is performed in advance during slurry formation to establish the crystal orientation before the firing process begins. This preliminary orientation establishment ensures that even when firing at lower temperatures that preserve orientation, the crystals are already aligned and will maintain this orientation throughout the extended low-temperature firing process.
Solution Approach 2:
The patent extends the firing duration continuously for 10 hours or more at the lower temperature. This continuous, extended heating process provides sufficient time for mass transfer and densification to occur at the lower temperature, ensuring that both crystal orientation is maintained and adequate sintered density (85% or higher) is achieved.
3Quantity of substance
If the holding time is extended to achieve sufficient mass transfer for sintering, then sintered density increases, but the extended high-temperature exposure causes crystal state disturbance
Solution Approach 1:
The patent fundamentally changes the temperature parameter from high to low (900°C to 1100°C range) while extending the time parameter. This parameter transformation allows the system to achieve the same mass transfer necessary for sintering but through a mechanism that does not involve the high-temperature atomic diffusion that would disturb crystal orientation. The extended holding time at low temperature provides sufficient diffusion distance for densification without disrupting the oriented crystal structure.
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 approach effectively maintains high crystal orientation and achieves high sintered density in piezoelectric oriented ceramics, suppressing crystal state disturbance and enabling sufficient mass transfer for sintering.
Implementation Method 1
obtaining a compact by forming the slurry in magnetic field
Implementation Method 2
mutual diffusion of Ti and Zr during a sintering process significantly disturbs a crystal state
Implementation Method 3
firing the compact, and in the step of firing the compact, the compact is held and fired for 24 hours or longer at a temperature lower by at least 100°C than a firing temperature lowest among firing temperatures
Data Source
Figure 1~2
Figure 3~4
AI summary
Piezoelectric oriented ceramics containing a Pb(Ti, Zr)O3-based compound as a compound having a perovskite structure and a method of manufacturing the same are provided. The piezoelectric oriented ceramics according to the present invention contains a Pb(Ti, Zr)O3-based compound having a perovskite structure. This piezoelectric oriented ceramics has a high degree of orientation not lower than 0.64, which was calculated with the Lotgering method based on an X-ray diffraction pattern in a prescribed cross-section thereof, and has sintered density not lower than 85% of theoretical density.