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What factors affect the piezoelectric properties of piezoelectric ceramic materials?
2025-06-09
The factors affecting the piezoelectric properties of piezoelectric ceramic materials mainly include the characteristics of the material itself, the preparation process and the external environmental conditions, as follows:
Composition and Crystal Structure of 1. Materials
The main crystal phase of piezoelectric ceramics with different chemical compositions (such as lead zirconate titanate PZT, barium titanate BaTiO, etc.) directly determines the piezoelectric properties. For example, the adjustment of the zirconium-titanium ratio (Zr/Ti) in PZT will change the Curie temperature and piezoelectric coefficient. When Zr/Ti is close to 52/48, the material is in the quasi-homotypic phase boundary and the piezoelectric performance is the best.
Doping elements (such as La, Nb, Sr, etc.) can change the degree of lattice distortion by replacing ions (such as Pb2, Ti, etc.) in the crystal lattice, thereby optimizing the piezoelectric performance. For example, La-doped PZT(PLZT) can improve the dielectric constant and the electro-optic effect.
The crystal structure of piezoelectric ceramics needs to have non-central symmetry (such as perovskite structure), and the phase transition process (such as from cubic phase to tetragonal phase) will significantly affect the piezoelectric properties. For example, BaTiO_3 in the Curie temperature (120 ℃) below by the cubic phase into the tetragonal phase, resulting in spontaneous polarization, piezoelectric coefficient increased significantly.
Preparation process and microstructure of 2.
Sintering process Sintering temperature and holding time affect the density and grain size of ceramics: too low temperature or too short time will lead to small grains, low density, poor piezoelectric properties. For example, the best sintering temperature of PZT ceramics is usually 1100-1300 ℃, at which time the grain size is uniform (5-10 μm), the density is> 95%, and the piezoelectric coefficient can reach 300-700 pC/N.
The sintering atmosphere (such as oxidation and reduction atmosphere) affects the ion valence state: PbO is volatile at high temperature, and it needs to be sintered in a lead-rich atmosphere to inhibit Pb vacancy defects and avoid the decline of piezoelectric properties.
Microstructure uniformity porosity, grain orientation and grain boundary characteristics are the key: pores will reduce the dielectric constant and mechanical strength, increase energy loss; through the texture process (such as template induced grain growth) to make the grain orientation arrangement, can enhance the anisotropy of piezoelectric properties (such as d increased by 30%-50%).
3. polarization condition
The polarization electric field strength needs to be applied higher than the material coercive field strength (E_c) of the polarization electric field (e. g., the E_c of PZT is about 20-30 kV/cm), so that the electric domain is aligned. When the electric field is insufficient, the polarization is insufficient and the piezoelectric coefficient is low; too high electric field may cause breakdown.
The polarization temperature and the time polarization temperature are usually close to the Curie temperature (such as PZT at 100-150°C) to reduce the rotation resistance of the electric domain. The holding time is generally 10-30 minutes. If the time is too short, the electric domain is not completely oriented, and if it is too long, there is no significant gain and energy consumption is increased.
4. external environmental factors
The temperature piezoelectric properties change significantly with temperature: when the temperature is lower than the Curie temperature, the temperature will increase the spontaneous polarization strength, the piezoelectric coefficient first slightly increased and then gradually decreased. For example, the Curie temperature of PZT is about 300 ° C., and the piezoelectric coefficient at 100 ° C. is about 10%-20% lower than that at room temperature (25 ° C.).
Mechanical stress static or dynamic stress will change the lattice distortion, affecting the polarization strength: compressive stress may enhance the piezoelectric response in some directions (such as when compressive stress is applied along the direction of polarization, dLoveri increases), but excessive stress will lead to irreversible inversion of the electric domain and performance degradation.
Electric Field and Time Aging Long-term application of alternating electric field may lead to electric domain fatigue and piezoelectric coefficient attenuation (for example, PZT may decrease by 10%-30% after 10 cycles); In addition, the "time aging" effect of the material itself (the electric domain gradually relaxes after polarization) will also cause the performance to decline slowly with time, which usually needs to be improved by annealing treatment.
5. other factors
Defects and impurities Lattice defects (e. g., vacancies, dislocations) and impurities (e. g., Fe, Si) can scatter domain motion, increase dielectric loss, and reduce piezoelectric properties. For example, the substitution of Fe3 for Ti3 in PZT introduces deep level traps that inhibit polarization reversal.
Size effect When the size of the material is reduced to the nanometer or micron level (such as piezoelectric ceramic film, nanofiber), the surface effect and quantum confinement effect will change the piezoelectric performance. For example, PZT films (thickness summary
The piezoelectric properties of piezoelectric ceramics are the result of the combination of the intrinsic properties of the material, the preparation process and the external conditions. Optimizing chemical composition, controlling microstructure, precisely regulating the polarization process, and combining application scenarios to resist environmental interference (such as temperature and stress) are the key directions for improving piezoelectric performance.
