Piezoelectric effect
Some materials cause polarization due to the relative displacement of the center of the positive and negative charges under the action of mechanical stress, which leads to the phenomenon of oppositely bound charges on the two ends of the material, called the piezoelectric effect. Conversely, when such materials are subjected to an external electric field, the internal positive and negative charge centers are displaced, which may cause mechanical deformation of the material. The magnitude of the deformation is proportional to the electric field strength. A ceramic having such properties is called a piezoelectric ceramic, and its surface charge density is proportional to the mechanical stress it receives.
Piezoelectric Ceramics
As a raw material of piezoelectric ceramics, crystals must have crystals having no center of symmetry, such as lead oxide, zirconium oxide, titanium oxide, barium carbonate, cerium oxide, magnesium oxide, zinc oxide, and the like. Commonly used piezoelectric ceramics are barium titanate, lead titanate, lead zirconate titanate, and ternary piezoelectric ceramics. Its structural types are perovskite type, tungsten bronze type, pyrochlore type, and bismuth layer structure.
The general process flow of piezoelectric ceramics production:
Piezoelectric ceramics are new functional electronic materials. With the continuous research and improvement of materials and processes, they have been widely used in sensors, transducers, non-destructive testing and communication technologies. To achieve the excellent performance of piezoelectric ceramics, it is necessary to process components with certain shape accuracy and dimensional accuracy. Therefore, research on the processing technology of piezoelectric ceramics, especially precision and ultra-precision machining technology, has great application value and practical significance.
Although piezoelectric ceramic materials have superior performance unmatched by other materials, they also have significant disadvantages - brittleness. Under the action of external force, no significant deformation will destroy, making it difficult to machine like ordinary materials, and the processing cost is higher than that of ordinary materials. Therefore, in the cutting of piezoelectric ceramics, it is necessary to select an appropriate cutting machine according to the appearance size, cutting size and precision requirements of the sample.
STX-202 small diamond wire cutting machine with micrometer
Cutting
Sticky sample. The sample was fixed on the carrier plate using a heating platform, paraffin, and graphite. For the cylindrical sample to be bonded to the side, add graphite on both sides to ensure the stability of the sample during cutting.
Install the card to the knife. Whether you use a wire saw or a saw blade, you need to adjust the position of the cutting edge. And most cutting machines can achieve a good verticality of the cutting surface. For example, the STX-202 small diamond wire cutter can perform high-parallel and vertical adjustment of samples through a 360° rotating platform and secondary card loading.
Adjustment parameters. Set the operating parameters of the cutting machine according to the relevant parameters of the sample to obtain the best cutting.
Grinding and polishing
For the sheet that needs to be glued, pay attention to the flatness of the surface, and clean the excess paraffin at the edge of the sheet to avoid cross-contamination with the abrasive and affect the grinding and polishing effect. At the same time, in order to remove abrasives and sundries that may be attached to other sizes of abrasive discs, each type of abrasive should be repaired first, but it is recommended that each type of abrasive should correspond to one disc to ensure the best grinding and polishing. effect. The abrasive is selected from corundum, and the grinding is carried out in the order of W28, W14, and W7.
Grinding and polishing
Corundum
Corundum
Corundum
Diamond suspension
granularity
(μm)
W28
W14
W7
3
pressure
( kg)
1.69
1.69
1.69
1.69
Number of revolutions
( rpm)
30
30
30
110
time
(min)
20
20
20
30
For the polishing of piezoelectric ceramics, a polyurethane polishing pad, a synthetic leather polishing pad, and a 3 μm diamond suspension are used. Note that the polishing pad should be spread evenly when it is pasted, so as to eliminate the bubbles on the bonding surface and ensure the smoothness of the polished surface. And before the official polishing, use the water to clean and then repair the pad, to avoid the sharp edges of the polishing pad is too sharp, damage the polished surface. In addition, to achieve a smaller surface roughness, a new polishing pad can be replaced after the first polishing is completed, and the polishing is continued using a 1.5 μm diamond suspension.
This process is not only suitable for cutting and polishing of piezoelectric ceramics, but also can be used for cutting, grinding and polishing of other ceramics by changing the corresponding parameter settings.
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