PMN-PZT ceramic and preparation method and application thereof

Abstract

The invention provides a preparation method of a PMN-PZT ceramic, which comprises the following steps: mixing Pb3O4 powder, SrCO3 powder, ZrO2 powder, TiO2 powder, Mg (OH) 2 powder, Nb2O5 powder and Sm2O3 powder, carrying out ball milling, pre-sintering, carrying out ball milling again after pre-sintering, adding a binder, carrying out granulation, carrying out formation after granulation, carrying out glue discharging, and sintering to obtain the PMN-PZT ceramic of Pb0. 92Sr0. 08 [(Mg1 / 3Nb2 / 3) 0.25-(Zr0. 491 Ti0. 509) 0.75] O3 + xmol% Sm, wherein x is not less than 0.1 and not more than 0.4; the adding amount of the Pb3O4 powder exceeds 2mol% of the stoichiometric ratio of the Pb3O4 powder. The invention also provides the PMN-PZT ceramic and an application of the PMN-PZT ceramic.

Description

Technical Field

[0001] This invention belongs to the field of piezoelectric ceramics, specifically relating to a PMN-PZT ceramic, its preparation method, and its application. Background Technology

[0002] All-solid-state high-energy laser technology has significant application prospects in high-end equipment manufacturing, high-energy-density science, and fusion energy, bringing substantial economic and social benefits. Among these, transparent electro-optic ceramics for high-energy laser modulators offer advantages such as low optical loss, high optical uniformity, and high reliability. Currently, transparent electro-optic ceramics, represented by lead magnesium niobate-lead zirconate-lead titanate (PMN-PZT), possess both piezoelectricity and optical transmittance, and are considered candidate materials for high-energy laser modulators. PMN-PZT is a relaxor ferroelectric-based transparent ceramic formed by introducing lead magnesium niobate (PMN) into traditional lead zirconate titanate (PZT) piezoelectric ceramics. Its key feature is the utilization of the high dielectric constant and diffusion phase transition characteristics of the PMN composition, combined with the strong piezoelectric response of the PZT system. Under specific composition and sintering processes, high optical transmittance and certain piezoelectric properties can coexist. This material typically employs advanced preparation techniques such as hot-pressing sintering or atmosphere sintering to reduce pores and grain boundary scattering, thereby exhibiting good transparency in the visible to near-infrared band. However, the current piezoelectric properties of PMN-PZT are insufficient to support high-efficiency, high-bandwidth laser modulators. Summary of the Invention

[0003] The first objective of this invention is to provide a method for preparing PMN-PZT ceramics for manufacturing electro-optical ceramics.

[0004] The second objective of this invention is to provide a PMN-PZT ceramic for manufacturing electro-optical ceramics.

[0005] A third objective of this invention is to provide an application of PMN-PZT ceramics for manufacturing electro-optical ceramics.

[0006] This invention is achieved through the following technical solution: A method for preparing PMN-PZT ceramics includes the following steps: Pb3O4 powder, SrCO3 powder, ZrO2 powder, TiO2 powder, Mg(OH)2 powder, Nb2O5 powder, and Sm2O3 powder were mixed and ball-milled, then pre-fired. After pre-firing, the mixture was ball-milled again, and a binder was added for granulation. After granulation, the mixture was formed, debinded, and then sintered to obtain Pb. 0.92 Sr 0.08 [(Mg 1 / 3 Nb 2 / 3 ) 0.25 -(Zr 0.491 Ti 0.509 )0.75 PMN-PZT ceramics with O3+xmol%Sm; Where 0.1 ≤ x ≤ 0.4; In the PMN-PZT ceramic, the proportion of ferroelectric domains smaller than 1 micrometer is 65-90%.

[0007] The amount of Pb3O4 powder added exceeded 2 mol of its stoichiometric ratio.

[0008] The ball milling medium used includes ethanol.

[0009] The ball milling time is 6 hours.

[0010] The preheating temperature is 800-850℃.

[0011] The adhesive comprises a polyvinyl alcohol solution; The concentration of the adhesive is 6 wt%.

[0012] The molding pressure is 127 MPa.

[0013] The temperature for discharging the adhesive is 650℃.

[0014] The temperature for sintering the embedded powder is 1200℃; The embedded powder used in the sintering process includes Pb3O4 powder, SrCO3 powder, ZrO2 powder, TiO2 powder, Mg(OH)2 powder, and Nb2O5 powder, and the proportions of each component are the same as those of the raw materials.

[0015] PMN-PZT ceramics prepared by the aforementioned method.

[0016] One application of the aforementioned PMN-PZT ceramic is in the fabrication of laser modulators.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows: The method provided in this invention prepares PMN-PZT ceramics with low Sm doping using a solid-state reaction method. By doping with 0.1-0.4 mol% Sm, the properties of the ceramic are effectively adjusted. d 33 .

[0018] The method provided by this invention prepares ceramics that are embedded and fired using special powder. d 33 =665pC / N. Attached Figure Description

[0019] Figure 1 (a) shows the XRD patterns of PMN-PZT ceramics with different Sm contents; Figure 1 (b) shows an enlarged view when 2θ = 44° - 46°. Figure 1 (c) shows the Rietveld refinement of the XRD pattern prepared in Comparative Example 1; Figure 1 (d) shows the Rietveld refinement of the XRD pattern prepared in Example 1; Figure 1 (e) shows the Rietveld refinement of the XRD pattern prepared in Example 2; Figure 1 (f) shows the Rietveld refinement of the XRD pattern prepared in Example 3; Figure 1 (g) shows the Rietveld refinement of the XRD pattern prepared in Example 4; Figure 1 (h) shows the variation of the perovskite phase fraction under different Sm contents; Figure 1 (i) shows the lattice parameters and tetragonality (c / a) of the perovskite phase under different Sm contents; Figure 2 (a) Shows all samples at 150–2200 cm⁻¹ -1 Raman spectra in the wavenumber range; Figure 2 (b) shows all samples at 150–900 cm⁻¹ -1 Raman spectra in the wavenumber range; Figure 2 (c) Shows all samples at 900–2200 cm⁻¹ -1 Raman spectra in the wavenumber range; Figure 2 (d) shows the variation of Itetra (%) (relative proportion of T phase) with Sm doping amount for all samples; Figure 3 (a) shows a SEM image of the PMN-PZT ceramic prepared in Comparative Example 1; Figure 3 (b) shows a SEM image of the PMN-PZT ceramic prepared in Example 1; Figure 3 (c) shows a SEM image of the PMN-PZT ceramic prepared in Example 2; Figure 3 (d) shows a SEM image of the PMN-PZT ceramic prepared in Example 3; Figure 3 (e) shows a SEM image of the PMN-PZT ceramic prepared in Example 4; Figure 3 (f) shows the average grain size of the PMN-PZT ceramics prepared in Examples 1-4 and Comparative Example 1; Figure 4 (a) shows the XPS spectra of PMN-PZT ceramics prepared in Examples 1-4 and Comparative Example 1; Figure 4 (b) shows the Pb 4f XPS spectra of the PMN-PZT ceramics prepared in Examples 1-4 and Comparative Example 1; Figure 5 (a) shows the O1s XPS spectrum of the PMN-PZT ceramic prepared in Comparative Example 1; Figure 5 (b) shows the O1s XPS spectrum of the PMN-PZT ceramic prepared in Example 1; Figure 5 (c) shows the O1s XPS spectrum of the PMN-PZT ceramic prepared in Example 2; Figure 5 (d) shows the O1s XPS spectrum of the PMN-PZT ceramic prepared in Example 3; Figure 5 (e) shows the O1s XPS spectrum of the PMN-PZT ceramic prepared in Example 4; Figure 5 (f) shows the area ratio of OV / (OL+OV) of the PMN-PZT ceramics prepared in Examples 1-4 and Comparative Example 1; Figure 6 (a) shows the PMN-PZT ceramics prepared in Examples 1-4 and Comparative Example 1. d 33 and ε r ; Figure 6 (b) shows the PMN-PZT ceramics prepared in Examples 1-4 and Comparative Example 1. k p and tan δ (%); Figure 7 (a) shows the amplitude image of the PMN-PZT ceramic prepared in Comparative Example 1; Figure 7 (b) shows an amplitude image of the PMN-PZT ceramic prepared in Example 1; Figure 7 (c) shows an amplitude image of the PMN-PZT ceramic prepared in Example 2; Figure 7 (d) shows the amplitude image of the PMN-PZT ceramic prepared in Example 3; Figure 7 (e) shows the amplitude image of the PMN-PZT ceramic prepared in Example 4; Figure 8 Hysteresis loop images of PMN-PZT ceramics prepared in Example 4 and Comparative Example 1 are shown. Figure 9 (a) shows the domain size data of the PMN-PZT ceramic prepared in Comparative Example 1; Figure 9 (b) shows the domain size data of the PMN-PZT ceramic prepared in Example 1; Figure 9 (c) shows the domain size data of the PMN-PZT ceramic prepared in Example 2; Figure 9 (d) shows the domain size data of the PMN-PZT ceramic prepared in Example 3; Figure 9 (e) shows the domain size data of the PMN-PZT ceramic prepared in Example 4; Figure 10 The defect types of Sm-PMN-PZT ceramics are shown. Detailed Implementation

[0020] Example 1 The molecular formula is Pb 0.92 Sr 0.08 [(Mg 1 / 3 Nb 2 / 3 ) 0.25 -(Zr 0.491 Ti 0.509 ) 0.75 Preparation of PMN-PZT ceramics with O3+ and 0.1 mol% Sm. The raw materials used were Pb3O4 (Adamas, 99.95%), SrCO3 (Adamas, 99%), ZrO2 (Adamas, 99%), TiO2 (Adamas, 99.99%), Mg(OH)2 (Adamas, 99%), Nb2O5 (Adamas, 99.99%), and Sm2O3 (Adamas, 99.9%).

[0021] To reduce the negative impact of lead volatilization during sintering, an excess of 2 mol% Pb3O4 was added during the sintering process. The raw materials were mixed according to stoichiometric ratio, ball-milled in ethanol for 6 hours, and the slurry was dried at 60°C for 12 hours. The resulting powder was calcined at 830°C for 2 hours, and then ball-milled and dried again using the same process. The powder was granulated using 6 wt% polyvinyl alcohol (PVA) as a binder. The granulated powder was pressed into green bodies with a diameter of 10 mm under a pressure of 127 MPa. These green bodies were then debinded at 650°C for 2 hours and sintered at 1200°C for 2 hours to obtain PMN-PZT ceramics.

[0022] Example 2 The molecular formula is Pb 0.92 Sr 0.08 [(Mg 1 / 3 Nb 2 / 3 ) 0.25 -(Zr 0.491 Ti 0.509 ) 0.75 Preparation of PMN-PZT ceramics with O3+ and 0.2 mol% Sm. The difference from Example 1 lies in the different raw material ratios.

[0023] Example 3 The molecular formula is Pb 0.92 Sr 0.08 [(Mg 1 / 3 Nb 2 / 3 ) 0.25 -(Zr 0.491 Ti 0.509 ) 0.75 Preparation of PMN-PZT ceramics with O3+ and 0.3 mol% Sm. The difference from Example 1 lies in the different raw material ratios.

[0024] Example 4 The molecular formula is Pb 0.92 Sr 0.08 [(Mg 1 / 3 Nb 2 / 3 ) 0.25 -(Zr 0.491 Ti 0.509 ) 0.75 Preparation of PMN-PZT ceramics with O3+ and 0.4 mol% Sm. The difference from Example 1 lies in the different raw material ratios.

[0025] Comparative Example 1 The molecular formula is Pb 0.92 Sr 0.08 [(Mg 1 / 3 Nb 2 / 3 ) 0.25 -(Zr 0.491 Ti0.509 ) 0.75 Preparation of PMN-PZT ceramics with O3. The difference from Example 1 lies in the different raw material ratios.

[0026] The ceramics prepared in the examples were tested using the following methods.

[0027] X-ray diffraction (XRD) patterns were collected using a Cu-Ka radiation diffractometer (MiniFlex600, Rigaku, Japan). Data were collected in the range of 20°–80° and then refined using Rietveld.

[0028] The surface morphology was examined using scanning electron microscopy (SEM, TESCAN). The chemical states of elements in the PMN-PZT samples were analyzed using X-ray photoelectron spectroscopy (XPS, Thermo Fisher Scientific, K-Alpha).

[0029] Raman spectroscopy was performed using a rapid micro Raman spectrometer (Thermo Fisher Scientific, DXR3) at a resolution of 150-2200 cm⁻¹. -1 Obtained using a 532 nm laser within the range.

[0030] Domain structures were observed using piezoelectric force microscopy (PFM) (Asylum Research, MFP-3D, USA).

[0031] To characterize the electrical properties, ceramic particles were polished to 0.65 mm, coated with Ag-Pt electrodes on both sides, and fired at 750°C for 10 minutes to form electrodes.

[0032] Using quasi-static piezoelectric d 33 The piezoelectric coefficient at room temperature was measured using a ZJ-3AN meter. The dielectric properties at room temperature were measured using an impedance analyzer (KEYSIGHT, E4990A).

[0033] The XRD patterns of PMN-PZT ceramics prepared in Examples 1-4 and Comparative Example 1 are shown below. Figure 1 As shown in (ab). From Figure 1 As can be seen from a, all samples exhibit a pure perovskite structure without any impurity phases, indicating that Sm 3+ The ions have been successfully dissolved in the PMN-PZT lattice. Figure 1(b) shows a magnified view of the (200) diffraction peak. All samples exhibit broad peaks near 2θ = 45°, indicating the coexistence of rhombic (R) and tetragonal (T) phases. With Sm doping, the (200) peak gradually splits into two distinct peaks. <200> and <002> This indicates an increase in the proportion of the T phase. Phase coexistence within the shape-bound phase boundary (MPB) region contributes to enhanced piezoelectric and dielectric properties of piezoelectric ceramics.

[0034] The doping content of Sm affects the phase structure. Rietveld refinement was performed on PMN-PZT ceramics using structural models of rhombic phase (space group R3c), monoclinic phase (space group Cm), and tetragonal phase (space group P4mm). The refinement results show that the P4mm + R3c mixed-phase model best fits the XRD data. The corresponding refined XRD patterns are shown below. Figure 1 As shown in (cg). Based on Rietveld refinement, Figure 1 (h) shows the evolution of the phase volume fractions of the R and T phases with the Sm doping content. As the Sm content increases, the T phase fraction rises from 56.5% to 78.33%, indicating that Sm doping significantly promotes the formation of the T phase. Figure 1 (i) Further, the variations in lattice parameters and unit cell volume of the tetragonal phase are shown. With increasing Sm doping level, the tetragonality (c / a) of the material shows a continuous increasing trend, consistent with the increase in T phase content, reflecting the significant influence of Sm doping on the evolution of the T phase structure. Previous studies have shown that Sm... 3+ Prioritize replacing Pb 2+ The ion at the a-site, not the ion at the b-site. Because of Sm 3+ Pb 2+ The smaller ionic radius leads to cell shrinkage. According to Bragg's law, the decrease in interplanar spacing causes the diffraction peaks to shift to higher angles.

[0035] Figure 2 (a) Shows the PMN-PZT ceramics prepared in Examples 1-4 and Comparative Example 1 at 150-2200 cm⁻¹. -1 Raman spectra within the wavenumber range. For detailed analysis, the entire spectrum was divided into sections from 150 to 900 cm⁻¹. -1 and 900-2200cm -1 Two areas, respectively as Figure 2 (b) and Figure 2 As shown in (c). For PZT-based ceramics, the Raman spectrum is in the range of 150–900 cm⁻¹. -1 The wavenumber range can be divided into two regions: the mid-frequency region (150-400 cm⁻¹) and the mid-frequency region. -1 ) and high frequency region (400~900 cm) -1 ).like Figure 2As shown in (c), at a wavenumber of 1020 cm⁻¹ -1 and 2050 cm -1 There are two Raman peaks nearby. All Raman spectra were obtained using 532 nm laser excitation, and rare earth ions readily exhibit fluorescence. These two peaks can be attributed to the fluorescence properties of samarium ions, confirming that samarium ions have successfully entered the lattice of PMN-PZT ceramics.

[0036] Raman spectroscopy analysis showed that all peaks exhibited broad peak characteristics, indicating the simultaneous presence of R and T phases in PMN-PZT ceramics. To investigate the effect of Sm doping on the phase evolution of PMN-PZT ceramics, a Gaussian function was used to analyze the 150-900 cm⁻¹ region. -1 Deconvolution fitting is performed on Raman spectra within the wavenumber range, such as... Figure 2 As shown in (b), there are three vibrational modes in the mid-frequency region: E(2TO), silent(E+B), and A1(2TO), and seven vibrational modes in the high-frequency region: E(2LO), E(3TO), R1, A1(3TO), E(3LO), Rh, and A1(3LO). Among these, the E(3TO), A1(3TO), E(3LO), and A1(3LO) modes are assigned to the tetragonal lattice vibrations, while the R1 and Rh modes are associated with the rhombic lattice. The fitting results confirm that all ceramic samples exhibit a coexistence of the T and R phases. To further reflect the changes in the relative content of the T and R phases, the relative intensity ratio of the T phase is introduced. I tetra (%) is used as the evaluation parameter. Its specific calculation is given by the following formula.

[0037] In the formula I The strength refers to I The subtitles in the lower right corner indicate the names of the vibration peaks: E(3LO) and A1(3LO). I R1 and I Rh These are the intensities of R1 and Rh, respectively. I tetra The percentage (relative proportion of T phase) varies with the Sm doping concentration as follows: Figure 2 As shown in (d). Compared with the undoped sample, the Sm-doped PMN-PZT ceramics... I tetra The significant increase in the percentage (%) indicates an increase in the relative content of the T phase. This result is consistent with the XRD refinement analysis results. These findings suggest that Sm doping effectively modulates the phase structure of PMN-PZT ceramics, promoting the development of the system towards a multiphase coexistence direction dominated by quadrilaterals.

[0038] Before characterizing the surface morphology of the ceramics, the samples were ground and polished until a scratch-free surface was achieved under an optical microscope, and then thermally etched at a temperature 150°C below the sintering temperature. The variations in surface morphology and average grain size with Sm doping concentration are shown below. Figure 3 As shown in (af). Microstructural analysis revealed that all ceramics exhibited clear microstructures. The grain size distribution of the undoped ceramics was uneven, while the introduction of Sm gradually improved the grain uniformity. At Sm doping concentrations of 0, 0.1, 0.2, 0.3, and 0.4 mol%, the corresponding average grain sizes were 3.13, 3.31, 3.03, 2.70, and 3.07 μm, respectively. Sm₂O₃ acts as both a donor dopant and a sintering aid; appropriate addition can effectively promote ceramic densification and reduce grain size.

[0039] During the sintering process of lead-based piezoelectric ceramics, the volatilization of PbO leads to lead vacancies ( ) and oxygen vacancies ( The formation of ) is shown in the following formula.

[0040] When Sm 3+ Replace Pb 2+ At this point, charge compensation is required to maintain electroneutrality, typically achieved through A-site vacancy compensation or oxygen vacancy annihilation mechanisms. This process is accompanied by an increase in lattice oxygen content. In perovskite-structured piezoelectric ceramics, the increased lattice oxygen content reduces the electron density around the metal atoms, leading to an increase in the binding energy of the Pb 4f orbitals, and a corresponding shift of the XPS peak to higher binding energies. This indicates that Sm 3+ It successfully entered the crystal lattice.

[0041] The deconvolution fitting of the O 1s XPS spectrum is as follows: Figure 5 As shown in (ae). The O 1s peak was fitted as two subpeaks: O located near 529.3 eV. L The peak and the O near 531.1 eV v The peaks represent lattice oxygen and oxygen vacancies, respectively. Using O v / (O L + O v The peak area ratio is used to quantitatively evaluate the relative concentration of oxygen vacancies. Changes in this ratio are shown in the figure. Figure 5 As shown in (f). After Sm doping, Sm 3+ Prioritize occupying position A, replacing Pb 2+ , forming a positively charged Defect centers. To maintain electroneutrality in the system, oxygen vacancies, as the primary mechanism for charge compensation, preferentially participate in the reaction, leading to a significant decrease in their concentration.

[0042] The properties of the PMN-PZT ceramics prepared in Examples 1-4 and Comparative Example 1 are as follows: Figure 6 As shown in (ab), as the Sm concentration increases from 0 mol% to 0.4 mol%, the PMN-PZT ceramic... d 33 The ratio gradually increases from 415 pC / N to 717 pC / N. PMN-PZT ceramics... ε r and dielectric loss (tan δ , %) showed with d 33 A similar trend. When the Sm doping concentration increases to 0.3 mol%, ε r The growth rate is significantly reduced. The electromechanical coupling coefficient k p Calculated using the following formula.

[0043] .

[0044] The resonant frequency (f) of a 0.65 mm thick ceramic sample was measured using an impedance analyzer (KEYSIGHT, E4990A). r ) and anti-resonant frequency (f a When the Sm concentration is 0.3 mol%, PMN-PZT ceramics... k p The highest value was 0.67, after which it decreased slightly.

[0045] To investigate the effect of Sm doping on domain structure, piezoelectric microscopy (PFM) was used to scan the 4 × 4 μm surface of all ceramic samples. 2 The region. The result is as follows: Figure 7 As shown in (ae), all samples exhibited an island-like domain structure, a typical characteristic of relaxor ferroelectrics. With increasing Sm doping concentration, the number of striped domains increased, indicating an increase in T-phase content. As Sm doping concentration increased, the continuity of ferroelectric domains was gradually disrupted, resulting in irregular nanoscale island-like domains. These nanodomains are considered manifestations of polar nanoregions (PNRs), indicating that Sm doping reduces the long-range order of ferroelectric domains, introduces local structural disorder, and promotes nanodomain formation. These PNRs can be reoriented and extended under relatively low external electric fields, contributing to enhanced piezoelectric response. Furthermore, when the ceramic composition is close to the formed phase boundary (MPB), the energy difference between different crystal phases is smaller, and the Gibbs free energy distribution becomes more uniform. This is beneficial for smaller domain size and higher domain density, thereby further improving piezoelectric performance. The PMN-PZT ceramics prepared in Example 4 and Comparative Example 1 were analyzed using single-frequency piezoelectric power microscopy (SS-PFM), as shown... Figure 8As shown, domain flipping was observed in the Sm-doped sample at a lower applied voltage of 3.5 V, compared to the 6 V required for the undoped sample. The results indicate that Sm doping effectively lowers the threshold voltage for domain flipping. Therefore, Sm binding is an effective strategy for customizing domain structures to improve piezoelectric properties.

[0046] As a typical ABO3-type perovskite material, PMN-PZT ceramics exhibit a variety of defect types during preparation and polarization processes, including lead vacancies, oxygen vacancies, and defect dipoles, such as... Figure 10 As shown, these defects significantly affect the dielectric behavior of the material. For example, the formation of lead vacancies can enhance domain wall mobility, making it easier for ferroelectric domains to switch under an external electric field, thereby improving the dielectric response.

[0047] according to Figure 7 When the Sm doping concentration reaches 0.3 mol%, Sm 3+ The incorporation of Sm disrupts the long-range order of ferroelectric domains, leading to lattice distortion. The resulting local inhomogeneities promote the formation of PNRs. Generally, PNRs are small in size and more easily polarized. Due to the presence of Sm... 3+ The ionic radius of PNRs is relatively small, and their density gradually increases with increasing doping level, leading to enhanced dipole mobility. Under a DC applied electric field, this enhanced dipole mobility results in a stronger dielectric response, macroscopically manifested as higher dielectric strength. ε r Furthermore, the local charge imbalance introduced by A-site rare earth doping disrupts the correlation between PNRs, reducing their correlation length and enhancing their dynamic response, thereby further improving dielectric properties. Simultaneously, the formation of PNRs introduces a local heterogeneous structure into the material, which helps lower the energy barrier between different phases, reducing polarization discontinuities and thus promoting dielectric response. Figure 9 As can be seen, the largest ferroelectric domain size in the undoped Sm ceramic sample is 7 μm, with approximately 54% being smaller than 1 μm. With increasing Sm content, the domain size gradually decreases to within 3 μm. For ceramics with Sm doping levels of 0.1-0.4 mol%, the proportion of domains smaller than 1 μm reaches 65%, 71%, 86%, and 90%, respectively. Sm incorporation significantly reduces domain size and promotes the formation of nanodomains. During sintering, the absence of samarium oxide is beneficial for maintaining a relatively balanced and fixed ratio of samarium ions to lead ions. This is because samarium oxide has a melting point as high as 2300℃, while lead oxide has a melting point of only 886℃. The absence of samarium oxide in the powder promotes the diffusion of samarium ions into the powder while inhibiting the volatilization of lead oxide, thereby maintaining a relatively balanced and fixed ratio of samarium ions to lead ions.

[0048] However, during polarization, some adjacent PNRs may merge, reducing their number and thus inhibiting the enhancement of dielectric properties to some extent. Furthermore, when the Sm concentration is 0.3 mol%, the T-phase content in the MPB increases to 68%. Compared to the R-phase domains, the T-phase domains have a higher polarization switching energy barrier, resulting in a weaker response to external electric fields, thereby preventing an increase in dielectric response. Meanwhile, as... Figure 3 As shown, this composition exhibits the smallest average grain size and the highest grain boundary density. The coupling between grain boundaries and domain walls constrains domain flipping, thus reducing the dielectric response. On the other hand, increasing Sm doping also leads to an increase in defect dipole concentration. The pinning effect of defect dipoles on ferroelectric domains restricts domain flipping and polarization processes, thereby affecting... ε r The increase will have an adverse effect.

[0049] In summary, under 0.3 mol% Sm doping conditions, the combined effects of phase transformation, grain refinement, defect pinning, and PNRs coalescence significantly offset the positive contributions of increased PNRs density and enhanced dipole activity, leading to ε r The growth of Sm is in a plateau phase. However, when the Sm doping concentration further increases to 0.4 mol%, the positive effects of factors such as increased grain size and a significant increase in the number of PNRs on the dielectric response become more pronounced, outweighing the negative effects caused by defects. Therefore, ε r Under this component, a faster growth trend was restored.

[0050] This invention successfully prepared a series of low-doped samarium (Sm) PMN-PZT ceramics using a solid-state reaction method, with doping levels ranging from 0.1 mol% to 0.4 mol%. X-ray diffraction (XRD) and Raman spectroscopy analyses showed that all samples were in a multiphase coexistence state. Further characterization by piezoelectric microscopy (PFM) revealed that 0.3 mol% Sm doping introduced significant local structural disorder and promoted the formation of piezoelectric nuclei (PNRs), thus enhancing the piezoelectric properties of the ceramics. When the Sm doping level reached 0.3 mol%, the PMN-PZT ceramic samples exhibited the best overall electrical performance. d 33 =665 pC / N, k p =0.67, relative permittivity ε r =2790.

Claims

1. A method for preparing PMN-PZT ceramics, characterized in that: Includes the following steps: Pb3O4 powder, SrCO3 powder, ZrO2 powder, TiO2 powder, Mg(OH)2 powder, Nb2O5 powder, and Sm2O3 powder were mixed and ball-milled, then pre-fired. After pre-firing, the mixture was ball-milled again, and a binder was added for granulation. After granulation, the mixture was formed, debinded, and then sintered to obtain Pb. 0.92 Sr 0.08 [(Mg 1 / 3 Nb 2 / 3 ) 0.25 -(Zr 0.491 Ti 0.509 ) 0.75 PMN-PZT ceramics with O3+xmol%Sm; Where 0.1 ≤ x ≤ 0.4; In the PMN-PZT ceramic, the proportion of ferroelectric domains smaller than 1 micrometer is 65-90%. The amount of Pb3O4 powder added exceeded 2 mol of its stoichiometric ratio.

2. The method for preparing PMN-PZT ceramics as described in claim 1, characterized in that: The ball milling medium used includes ethanol.

3. The method for preparing PMN-PZT ceramics as described in claim 1, characterized in that: The ball milling time is 6 hours.

4. The method for preparing PMN-PZT ceramics as described in claim 1, characterized in that: The preheating temperature is 800-850℃.

5. The method for preparing PMN-PZT ceramics as described in claim 1, characterized in that: The adhesive comprises a polyvinyl alcohol solution; The concentration of the adhesive is 6 wt%.

6. The method for preparing PMN-PZT ceramics as described in claim 1, characterized in that: The molding pressure is 127 MPa.

7. The method for preparing PMN-PZT ceramics as described in claim 1, characterized in that: The temperature for discharging the adhesive is 650℃.

8. The method for preparing PMN-PZT ceramics as described in claim 1, characterized in that: The temperature for sintering the embedded powder is 1200℃; The embedded powder used in the sintering process includes Pb3O4 powder, SrCO3 powder, ZrO2 powder, TiO2 powder, Mg(OH)2 powder, and Nb2O5 powder, and the proportions of each component are the same as those of the raw materials.

9. PMN-PZT ceramics prepared by the method described in claim 1.

10. The application of PMN-PZT ceramic as described in claim 9, characterized in that: It is used in the fabrication of laser modulators.

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