Sodium niobate-based ceramic for identifying lattice distortion and preparation method thereof

Abstract

The invention discloses sodium niobate-based ceramic for identifying lattice distortion and a preparation method of the sodium niobate-based ceramic, and belongs to the field of inorganic functional ceramic materials. The chemical general formula of the sodium niobate-based ceramic is (1-x) [0.85 (Na0. 94YbaTmb) NbO3-0. 15 (Bi0. 5Na0. 5) TiO3]-x (Ba0. 5Sr0. 5) (Sn0. 5Hf0. 5) O3, 0.01 < = alt, 0.01 < = alt, 0.01 < = alt, 0.01 < = alt, 0.01 < = alt, 0.01 < = alt, 0.01 < = alt, 0.01 < = alt, 0.01 < 0.02, 0.01 < = blt; 0.02 < = x < = 0.06. The preparation method comprises the following steps: (1) burdening and primarily mixing to obtain primarily mixed powder; (2) pre-sintering the primarily mixed powder, and mixing again to obtain uniform powder; (3) carrying out compression molding on the uniform powder; (4) removing organic matters; and (5) sintering to obtain the sodium niobate-based ceramic. The sodium niobate-based ceramic provided by the invention can realize lossless and high-spatial-resolution distortion detection, and achieves the effect of high sensitivity.

Description

TECHNICAL FIELD

[0001] The present application relates to inorganic functional ceramic materials, in particular, a sodium niobate-based ceramic for identifying lattice distortion and a preparation method thereof. BACKGROUND

[0002] Lattice distortion is a common phenomenon in which the arrangement of atoms in a solid material deviates from the ideal periodicity, resulting from internal and external factors such as stress, doping, phase transition, or defects. Accurate identification and quantification of lattice distortion are of great significance in basic scientific research (such as phase transition mechanism, defect engineering) and high-end engineering applications (such as structural health monitoring, stress field visualization, and early warning of micro-cracks). However, existing technologies face a series of severe challenges and bottlenecks in this field.

[0003] Firstly, the limitations of existing detection methods are prominent: Currently, mainstream technologies for characterizing lattice distortion, such as X-ray diffraction (XRD), neutron diffraction, and high-resolution transmission electron microscopy (HRTEM), can provide direct structural information, but have significant shortcomings: (1) Equipment dependency and high cost: These technologies rely on large, expensive specialized equipment, making it impossible to implement on-site, online, or distributed detection; (2) There is a risk of invasiveness and destructiveness: XRD usually requires grinding the sample, and the sample preparation process for HRTEM is complex and can only observe local micro areas, making it difficult to non-destructively evaluate the overall distortion state of large volumes or actual service components; (3) Insufficient sensitivity and real-time performance: Traditional diffraction methods have limited sensitivity to small, local, or dynamic changes in lattice distortion, especially non-uniform distortion, making it difficult to achieve real-time, dynamic monitoring.

[0004] Secondly, using optical signals (such as fluorescence peak position, intensity, and lifetime) to respond to stress or distortion is a promising non-destructive, remote sensing method, among which rare earth ion-doped upconversion luminescence materials have attracted attention due to their large Stokes shift, strong anti-interference ability, and high spatial resolution. However, existing fluorescent materials for stress / strain sensing (such as Al2O3:Cr 3+The following fundamental difficulties are faced by the current luminescence-based sensing materials (such as some fluoride-based upconversion nanoparticles): (1) signal singleness and low information dimension: most of the materials only rely on the shift of the luminescence peak position or the change of the intensity as the sensing signal, which is easily disturbed by environmental factors such as temperature, light source fluctuation, detection system stability, resulting in low signal-to-noise ratio, high false alarm rate, and especially difficult to distinguish the signal changes caused by temperature effect and real stress; (2) insensitivity to local lattice symmetry change: the conventional luminescence peak shift mainly reflects the overall expansion or compression of the lattice, i.e. macroscopic strain, and lacks specific response to microscopic distortion types such as local lattice symmetry breaking and bond angle distortion, which greatly limits its application value in complex stress field analysis and failure mechanism research; (3) poor compatibility between material system and matrix: the chemical and physical properties (such as thermal expansion coefficient and sintering activity) of many high-performance luminescence materials (such as rare earth-doped fluorides) are greatly different from widely used oxide ceramic matrices (such as piezoelectric ceramics and structural ceramics), which are difficult to be uniformly compounded as functional phase, or the interface problem is serious after compounding, resulting in poor signal reliability. SUMMARY

[0005] The purpose of the present application is to provide a sodium niobate-based ceramic for identifying lattice distortion, which can realize nondestructive and high spatial resolution distortion detection with high sensitivity. Another purpose of the present application is to provide a preparation method of the above-mentioned sodium niobate-based ceramic.

[0006] Technical scheme: The sodium niobate-based ceramic for identifying lattice distortion provided by the present application has a chemical formula of (1-x)[0.85(Na 0.94 Yb a Tm b )NbO3-0.15(Bi 0.5 Na 0.5 )TiO3]-x(Ba 0.5 Sr 0.5 )(Sn 0.5 Hf 0.5 )O3, wherein 0.01≤a<0.02, 0.01≤b<0.02, and 0.02≤x≤0.06.

[0007] The preparation method of the sodium niobate-based ceramic provided by the present application comprises the following steps: (1) dosing and preliminary mixing to obtain a preliminary mixed powder; (2) pre-sintering and re-mixing the preliminary mixed powder to obtain a uniform powder; (3) pressing the uniform powder into a shape; (4) removing organic matter; (5) sintering to obtain the sodium niobate-based ceramic.

[0008] The preliminary mixing in step (1) uses a wet ball milling process, the rotating speed is 390-420 rpm, and the ball milling time is 14-16 h. In the ball milling process, the grinding beads used are zirconium oxide balls with a size of 2-9 mm.

[0009] The pre-burning process in step (2) has a temperature rising rate of 2-3 °C / min, the highest temperature is 850-870 °C, and the holding time is 6-8 h; the mixed ball milling process has a ball milling time of 12-14 h.

[0010] The pressure for the press forming in step (3) is 320-360 MPa.

[0011] In step (4), the process conditions for removing the organic matter are: the temperature is raised to 600-650 °C at a rate of 1-3 °C·min -1 , and the holding time is 10-12 h.

[0012] In step (5), before sintering, a layer of the powder obtained in step (2) is uniformly spread on the surface of the material; the sintering process is to raise the temperature to 1200-1220 °C at a rate of 3-4 °C·min -1 , and the holding time is 5-6 h.

[0013] Invention principle: The present application introduces Yb 3+ -Tm 3+ ion pairs into a sodium niobate-based ceramic matrix to construct an efficient up-conversion luminescence system. Among them, Yb 3+ serves as a sensitizing agent to effectively absorb near-infrared light; Tm 3+ serves as an activator, and the 3 F 2,3 energy level is extremely sensitive to changes in the surrounding crystal field environment (i.e., local symmetry and coordination field strength). The positions and shapes of the light emission peaks corresponding to these energy level transitions, especially the Stark splitting pattern, can directly reflect the microsymmetry of the lattice site where the Tm 3+ ion is located. In addition, the present method introduces appropriate proportions of Bi 3+ (coordination number 12, 1.39 Å), Ba 2+ (coordination number 12, 1.61 Å) into the NaNbO3 system, which are special large-radius ions to enhance lattice distortion and change the crystal field, thereby helping to enhance the excitation of the 4 f orbit of Tm 3+ ion at a 980 nm excitation wavelength, split the originally degenerate 3 F 2,3 energy level, i.e., reduce the energy barrier of the split energy level by increasing the distortion entropy. The sub-energy levels after splitting have different energy differences from the ground state energy level, and new light emission peaks will appear when radiation transition occurs. Finally, the micro-scale deformation of the lattice distortion and the 3 F2,3 3 H6 corresponds to the band (about 680 nm) in the form of emission peak splitting, which realizes the effect of identifying lattice distortion by inducing upconversion emission peak. 3+ , Tm 3+ , Bi 3+ , Ba 2+ The four kinds of element ions cooperate with each other and synergistically.

[0014] Beneficial effects: compared with the prior art, the present application has the following significant advantages: (1) the method can identify lattice distortion by inducing upconversion emission peak, has high sensitivity, 3 F 2,3 The more obvious the related emission peak splitting is, the more serious the lattice distortion is; (2) the characteristic of identifying lattice distortion by inducing upconversion emission peak is little affected by temperature, and the emission peak splitting phenomenon exists stably in the temperature range of 273-673 K, and the corresponding lattice distortion also exists stably in the temperature range; (3) the method can generate optical signals with high-dimensional characteristics and specific response to local symmetry change, so as to resist interference and distinguish distortion types; (4) the method can realize real-time monitoring, non-invasive, high spatial resolution and specific identification of distortion types and degrees by collecting upconversion luminescence signals of specific wavelengths in real time, and overcomes the problems of expensive equipment, strong invasiveness and single signal in the prior art, and has potential application value in the field of in-situ health monitoring and early failure warning of major engineering structures; (5) the present application deeply integrates material science, spectroscopy and mechanical detection, creates a new paradigm of "material as sensor", and provides a ceramic sheet which can be directly attached or embedded into the inside of the structure to be measured, so that the in-situ, non-invasive and visual monitoring of the internal microscopic stress / strain field, early micro-crack initiation (accompanied by local stress concentration) and other hidden damages of large-volume components can be realized through remote light excitation and signal collection, which has irreplaceable application prospect and necessity in the field of structure health monitoring and safety warning in the fields of aerospace, precision manufacturing and energy equipment. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 XRD patterns of the ceramics prepared in Examples 1-3, Comparative Examples 1-2 and 6; Figure 2 SEM micrographs of the ceramics prepared in the present application, wherein 2a is Example 1, 2b is Comparative Example 1, 2c is Comparative Example 2, and 2d is Comparative Example 6; Figure 3 Upconversion photoluminescence signal diagram of the ceramics prepared in Examples 1 and Comparative Examples 1-6; Figure 4 XRD local diagram of the sodium niobate-based ceramics obtained in Example 1 and Comparative Example 1 in the temperature range of 50-450°C;​ Figure 5 is the partial spectrum of emission spectrum of the sodium niobate-based ceramic sample obtained in Example 1 in the temperature range of 273-673 K; Figure 6 is the full spectrum of emission peak of the sodium niobate-based ceramic sample obtained in Example 1 in the temperature range of 273-673 K; Figure 7 is the complex impedance diagram of the sodium niobate-based ceramic sample measured at 510 °C in Examples 1-3 and Comparative Example 1. DETAILED DESCRIPTION

[0016] The technical solutions of the present application are further described below in combination with examples.

[0017] Example 1

[0018] The sodium niobate-based ceramic described in the present application has a general chemical composition of 0.96[0.85(Na 0.94 Yb 0.01 Tm 0.01 )NbO3-0.15(Bi 0.5 Na 0.5 )TiO3]-0.04(Ba 0.5 Sr 0.5 )(Sn 0.5 Hf 0.5 )O3.

[0019] The preparation method of the sodium niobate-based ceramic described in the present application comprises the following steps: (1) batching and preliminary mixing: according to the general chemical composition (1-x)[0.85(Na 0.94 Yb 0.01 Tm 0.01 )NbO3-0.15(Bi 0.5 Na 0.5 )TiO3]-x(Ba 0.5 Sr 0.5 )(Sn 0.5 Hf 0.5)O3 stoichiometry, chemical formula takes x = 0.04, analytical pure raw material powders are weighed, including 2.2235 g Na2CO3, 5.4498 g Nb2O5, 0.8429 g Bi2O3, 0.1491 g SrCO3, 0.1522 g SnO2, 0.2105 g HfO2, 0.5868 g TiO2, 0.0805 g Yb2O3, 0.0788 g Tm2O3, 0.1975 g BaCO3. Zirconia balls with particle sizes of 2, 5, 7, and 9 mm are weighed in a mass ratio of 1.5:1.2:1:1, and are used as grinding media together with alcohol. Wet ball milling is performed at a ball-to-material ratio of 2:1, a rotation speed of 400 rpm, and for 14 h to fully mix the slurry. After the slurry is dried, it is ground in an agate mortar and sieved through a 150-mesh screen.

[0020] (2) Calcination: The mixed powders are placed in a corundum crucible and heated at a gradient of 2 °C / min -1 to 860 °C and held for 8 h to obtain the calcined product. The purpose of calcination is to avoid excessive shrinkage of the green body during the final sintering process, preventing stress concentration and the formation of microcracks. The calcined product is ball milled again for 13 h, with the specific parameters being the same as in step (1). After the ball milling is completed, the product is ground and sieved through a 100-mesh screen to obtain a uniform powder for forming, which is also referred to as the base powder.

[0021] (3) Granulation and forming: 7.5 wt% polyvinyl alcohol binder is added to the powder and thoroughly ground to ensure complete mixing. The mixture is then dried at 75 °C for 30 min to remove excess moisture. After grinding and sieving, uniform granules are obtained. Hard alloy molds are used to press form the green body under a biaxial pressure of 350 MPa, resulting in cylindrical green bodies with a diameter of Φ10 ± 0.05 mm and a thickness of 1.0 ± 0.1 mm.

[0022] (4) Removal of organic matter: The formed green body is placed in a muffle furnace in an air atmosphere and heated at a rate of 3 °C / min -1 to 600 °C and held for 10 h to ensure complete thermal decomposition of the organic matter.

[0023] (5) High-temperature sintering: To reduce the volatilization of Bi 3+ , Na + , and other elements during sintering, a layer of the base powder obtained in step (2) is uniformly spread on the surface of the material before sintering. A multi-temperature zone sintering process is adopted, with a heating rate of 4 °C / min -1 to 1220 °C and a holding time of 5 h to achieve ceramic densification, resulting in a sodium niobate-based ceramic. This sample is named x = 0.04.

[0024] Example 2

[0025] The same as example 1 will not be repeated, the difference is that: x = 0.02, the raw material powder includes 2.2698g Na2CO3, 5.5633g Nb2O5, 0.8605g Bi2O3, 0.0746g SrCO3, 0.0761g SnO2, 0.1052g HfO2, 0.5991g TiO2, 0.0821g Yb2O3, 0.0805g Tm2O3, 0.0987g BaCO3; the ball milling speed and time in step (1) are 410 rpm and 16h respectively; the pre-sintering highest temperature and holding time in step (2) are 870°C and 6h respectively, and the re-milling time is 14h; the drying temperature in step (3) is 85°C, and the pressing pressure is 320MPa; the heating rate in step (4) is 1°C·min -1 ; the sintering condition in step (5) is heated to 1200°C at a heating rate of 3°C·min -1 and holding for 5h. The obtained ceramic is named as x = 0.02.

[0026] Example 3

[0027] The same as example 1 will not be repeated, the difference is that: x = 0.06, the raw material powder includes 2.2177g Na2CO3, 5.3362g Nb2O5, 0.8254g Bi2O3, 0.2237g SrCO3, 0.2284g SnO2, 0.3157g HfO2, 0.5746g TiO2, 0.0788g Yb2O3, 0.0772g Tm2O3, 0.2962g BaCO3; the ball milling speed and time in step (1) are 410 rpm and 16h respectively; the pre-sintering condition in step (2) is heated to 870°C at a heating rate of 3°C·min -1 and holding for 6h, and the re-milling time is 12h; the highest temperature and holding time in step (4) are 650°C and 12h respectively; the heating rate in step (5) is 4°C·min -1 . The obtained ceramic is named as x = 0.06.

[0028] Comparative Example 1 The same as example 1 will not be repeated, the difference is that: x = 0, the raw material powder includes 2.3162g Na2CO3, 5.6768g Nb2O5, 0.8781g Bi2O3, 0.6112g TiO2, 0.0838g Yb2O3, 0.0821g Tm2O3; the ball milling speed and time in step (1) are 380 rpm and 12h respectively; the pre-sintering condition in step (2) is heated to 870°C at a heating rate of 3°C·min -1heated to 820 °C at a heating rate of 5 °C / min and held for 7 h, the second ball-milling time was 14 h; the pressing pressure in step (3) was 300 MPa; the holding time in step (4) was 9 h; the highest temperature and the holding time in step (5) were 1190 °C and 4 h, respectively. The obtained ceramic was named x=0.

[0029] Comparative Example 2 The same as in Example 1 was not repeated, the difference was that: the chemical composition general formula was (Na 0.94 Yb 0.01 Tm 0.01 )NbO3, the analytical pure raw material powder was weighed according to the stoichiometric ratio, including 2.9411 g Na2CO3, 6.6786 g Nb2O5, 0.0966 g Tm2O3, 0.0986 g Yb2O3; the ball-milling speed and time in step (1) were 360 rpm and 10 h, respectively; the holding time in step (2) was 7 h, and the second ball-milling time was 12 h; the drying temperature in step (3) was 85 °C, and the pressing pressure was 280 MPa; the holding time in step (4) was 8 h; the highest temperature and the holding time in step (5) were 1180 °C and 3 h, respectively. The obtained ceramic was named NN-1YT.

[0030] Comparative Example 3 The same as in Example 1 was not repeated, the difference was that: the doping amounts of Yb and Tm elements were both 0, the chemical composition general formula was 0.96[0.85NaNbO3-0.15(Bi 0.5 Na 0.5 )TiO3]-0.04(Ba 0.5 Sr 0.5 )(Sn 0.5 Hf 0.5 )O3, the analytical pure raw material powder was weighed according to the stoichiometric ratio, including 2.3532 g Na2CO3, 5.4498 g Nb2O5, 0.8429 g Bi2O3, 0.1491 g SrCO3, 0.1522 g SnO2, 0.2105 g HfO2, 0.5868 g TiO2, 0.1975 g BaCO3; the ball-milling speed and time in step (1) were 370 rpm and 15 h, respectively; the second ball-milling time in step (2) was 14 h. The obtained ceramic was named 0%Yb0%Tm.

[0031] Comparative Example 4 The same as in Example 1 was not repeated, the difference was that: the doping amounts of Yb and Tm elements were 3% and 0, respectively, the chemical composition general formula was 0.96[0.85(Na 0.91 Yb 0.03 )NbO3-0.15(Bi 0.5Na 0.5 )TiO3]-0.04(Ba 0.5 Sr 0.5 )(Sn 0.5 Hf 0.5 )O3, the analytical pure raw material powder is weighed according to the stoichiometric ratio, including 2.1586g Na2CO3, 5.4498g Nb2O5, 0.8429g Bi2O3, 0.1491g SrCO3, 0.1522g SnO2, 0.2105g HfO2, 0.5868g TiO2, 0.2414g Yb2O3, 0.1975g BaCO3. The obtained ceramic is named as 3%Yb0%Tm.

[0032] Comparative Example 5 The same as that of Example 1 is not repeated, and the difference lies in that the doping amounts of Yb and Tm elements are 0 and 3% respectively, and the general chemical composition formula is 0.96[0.85(Na 0.91 Tm 0.03 )NbO3-0.15(Bi 0.5 Na 0.5 )TiO3]-0.04(Ba 0.5 Sr 0.5 )(Sn 0.5 Hf 0.5 )O3, the analytical pure raw material powder is weighed according to the stoichiometric ratio, including 2.1586g Na2CO3, 5.4498g Nb2O5, 0.8429g Bi2O3, 0.1491g SrCO3, 0.1522g SnO2, 0.2105g HfO2, 0.5868g TiO2, 0.2414g Yb2O3, 0.1975g BaCO3. The obtained ceramic is named as 3%Yb0%Tm.

[0033] Comparative Example 6 The same as that of Example 1 is not repeated, and the difference lies in that the doping amounts of Yb and Tm elements are both 2%, and the general chemical composition formula is 0.96[0.85(Na 0.88 Yb 0.02 Tm 0.02 )NbO3-0.15(Bi 0.5 Na 0.5 )TiO3]-0.04(Ba 0.5 Sr 0.5 )(Sn 0.5 Hf 0.5)O3, weigh analytical grade raw material powder according to the stoichiometric ratio, including 2.094g Na2CO3, 5.4498g Nb2O5, 0.8429g Bi2O3, 0.1491g SrCO3, 0.1522g SnO2, 0.2105g HfO2, 0.5868g TiO2, 0.1609g Yb2O3, 0.1576g Tm2O3, and 0.1975g BaCO3. Name the resulting ceramic 2%Yb2%Tm.

[0034] The ceramic samples obtained by this invention were subjected to performance tests. The mechanically thinned samples to the required thickness and polished were placed in centrifuge tubes containing anhydrous ethanol. The centrifuge tubes were then cleaned in an ultrasonic cleaner. After 10 minutes, they were removed, dried, and then subjected to performance tests. To ensure test consistency, the thickness of the upconversion photoluminescence test samples was controlled below 0.6 mm, and the thickness of the impedance performance test samples was controlled between 0.4 and 0.6 mm.

[0035] according to Figure 1 The XRD patterns show that when Yb and Tm are simultaneously doped at a concentration of 1% using this method (Examples 1-3, Comparative Examples 1-2), the sodium niobate-based ceramics prepared have a single perovskite structure. When Yb and Tm are not added simultaneously, or when their doping concentration is higher (Comparative Example 6), a single perovskite structure cannot be formed, and multiple impurity peaks can be observed around 27-31° in the figure.

[0036] Figure 2 The SEM morphology of the samples is shown. It is observed that the NN-1YT sample (Comparative Example 2) has a larger grain size and is doped with Bi. 3+ The grain size of the subsequent (Comparative Example 1) sample decreased, and the Ba doping... 2+ The grain size of the subsequent sample (Example 1) was further reduced. This phenomenon is attributed to the "pinning" effect induced by ions dissolving into the sodium niobate lattice, which significantly inhibits grain growth. However, when the doping concentration of Yb and Tm reached 2% (Comparative Example 6), impurity phase grains with significant differences in shape and size could be identified, marked with red circles in the figure. The appearance of impurity phases indicates that rare earth elements Yb and Tm were not completely dissolved into the lattice, which is not conducive to the purpose of identifying lattice distortion through emission peak splitting. By repeatedly controlling the doping concentration, this invention formed a stable pure perovskite phase in Example 1, solving the problem of poor compatibility between the material system and the matrix.

[0037] analyze Figure 3 It can be seen that, at room temperature, when the NN-1YT sample (Comparative Example 2) is irradiated with a fixed excitation wavelength of 980 nm, only one particle can be resolved near 680 nm. 3 H 2,3Upconversion photoluminescence peaks related to the energy level radiation transition, which represents that the sodium niobate lattice is ordered and no distortion occurs; doped with Bi 3+ After (Comparative Example 1), it is found that the emission peak near 680 nm begins to split, and there is one complete and 3 H 2,3 energy level to the ground state 3 H6Upconversion photoluminescence peaks related to the energy level radiation transition split into three fuzzy emission peaks, which represents that the atomic disorder degree increases and the lattice begins to distort as the aliovalent ions enter the sodium niobate lattice; further doped with Ba 2+ After (Example 1), it is found that the emission peak near 680 nm splits very obviously, and there is one complete and 3 H 2,3 Upconversion photoluminescence peaks related to the energy level radiation transition split into three clear emission peaks, which represents that the atomic disorder degree increases sharply and the lattice distortion is more serious as the aliovalent ions enter the sodium niobate lattice. Through the comparison of Example 1 and Comparative Examples 1-2, the lattice distortion can be corresponded to the splitting of the emission peak, and it is concluded that the more serious the distortion is, 3 F 2,3 the more obvious the splitting of the related emission peak is. In addition, when the doping amounts of Yb and Tm elements are both 0 (Comparative Example 3), no light emission peak is observed in the collection range of 400-730 nm; when the doping amounts of Yb and Tm elements are 3% and 0 respectively (Comparative Example 4), only a narrow light emission peak near 490 nm is presented in the collection range of 400-730 nm, which corresponds to the virtual energy level transition of two Yb 3+ ions cooperating; when the doping amounts of Yb and Tm elements are 0 and 3% respectively (Comparative Example 5), light emission peaks of specific wavebands can be observed in the collection range of 400-730 nm, but since there is no Yb 3+ as a sensitizing agent to provide an auxiliary energy transmission channel, the light emission intensity is very weak, so the light emission peak near 680 nm is 3 F 2,3 related to the signal confusion and noise, which greatly reduces the reliability of light emission signal collection; when the doping amounts of Yb and Tm elements are both 2% (Comparative Example 6), light emission peaks of specific wavebands near 480 and 680 nm can be observed in the collection range of 400-730 nm, and the light emission signal is stable without obvious noise points, but excessive Yb and Tm cannot be stably solid-solved into the NaNbO3 lattice, resulting in that the splitting of the light emission peak near 680 nm is not obvious. Therefore, it is known that Yb 3+ , Tm 3+ , Bi 3+ , Ba 2+The four kinds of element ions produce synergistic effect in the sodium niobate-based ceramic, and the lattice distortion can be recognized by splitting of up-conversion luminescence peak. The ceramic is placed in different environmental conditions, and as long as the pulsed laser is emitted, the up-conversion luminescence signal can be collected all the time, and as long as the luminescence signal is collected all the time, the lattice distortion can be judged by analyzing the splitting of the luminescence peak, and the whole process does not affect the normal working state of the ceramic, and is dynamic and real-time.

[0038] Figure 4 The evolution law of the XRD strongest peak (2 θ ~32.6°) of the sample in the range of 0-450°C is collected, and the sodium niobate-based ceramic is simultaneously doped with Yb and Tm elements and the doping amount is 1%, but not doped with Ba 2+ (Comparative Example 1), and the results show that the diffraction peak gradually combines from the double peak at room temperature to a single peak; after doping Ba 2+ (Example 1), the results show that the diffraction peak always maintains a single shape, and the half-peak width does not fluctuate obviously, indicating that the sample has a wide temperature range of structural stability.

[0039] Figures 5-6 The evolution law of the splitting degree of the emission peak of the sample obtained in Example 1 with temperature change is tested, and the emission peak splitting caused by the structural distortion stably exists in the temperature range of 273-673K, which has potential conditions for further development into an optical lattice distortion sensor.

[0040] Figure 7 The complex impedance spectrum of the sample is shown, the total resistance of the sample with x=0 (Comparative Example 1) is the lowest, and is proportional to the intercept of the x-axis, corresponding to the reliability of low electric breakdown resistance, indicating that further modification is necessary; the total resistance of the sample with x=0.02 (Example 2) is higher than that of the sample with x=0, corresponding to the improved electric breakdown resistance reliability, indicating that the formula design of the present application is reasonable; the total resistance of the sample with x=0.04 (Example 1) is significantly higher than that of the sample with x=0, corresponding to excellent electric breakdown resistance reliability; the total resistance of the sample with x=0.06 (Example 3) is significantly higher than that of the sample with x=0.04, corresponding to further improved electric breakdown resistance reliability.

Claims

1. A sodium niobate-based ceramic for identifying lattice distortion, characterized in that, The general chemical formula of the sodium niobate-based ceramic is (1-x)[0.85(Na)]. 0.94 Yb a Tm b )NbO3-0.15(Bi 0.5 Na 0.5 TiO3]-x(Ba 0.5 Sr 0.5 (Sn) 0.5 Hf 0.5 )O3, where 0.01≤a<0.02, 0.01≤b<0.02, 0.02≤x≤0.

06.

2. A method for preparing sodium niobate-based ceramics according to claim 1, characterized in that, Includes the following steps: (1) Ingredients are prepared and initially mixed to obtain a preliminary powder; (2) The initial powder mixture is pre-fired and then mixed again to obtain a uniform powder; (3) Press the uniform powder into shape; (4) Eliminate organic matter; (5) Sintering to obtain sodium niobate-based ceramics.

3. The preparation method according to claim 2, characterized in that, The preliminary mixing in step (1) uses a wet ball milling process with a rotation speed of 390-420 rpm and a milling time of 14-16 h.

4. The preparation method according to claim 2, characterized in that, The pre-firing process described in step (2) has a heating rate of 2-3°C / min, a maximum temperature of 850-870°C, and a holding time of 6-8h.

5. The preparation method according to claim 2, characterized in that, The pressing pressure described in step (3) is 320-360 MPa.

6. The preparation method according to claim 2, characterized in that, The process conditions for removing organic matter described in step (4) are: 1-3°C·min -1 The temperature is increased to 600-650°C at a rate and held for 10-12 hours.

7. The preparation method according to claim 2, characterized in that, In step (5), before sintering, a layer of powder obtained in step (2) is evenly spread on the surface of the material.

8. The preparation method according to claim 2, characterized in that, The sintering process described in step (5) is at 3-4°C·min. -1 Heat the temperature to 1200-1220°C at a rapid rate and hold for 5-6 hours.

9. The preparation method according to claim 3, characterized in that, In the ball milling process described above, the grinding beads used are 2-9mm zirconia balls.

10. The preparation method according to claim 2, characterized in that, The ball milling process described in step (2) involves a milling time of 12-14 hours.

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