Niobium-added strontium titanate single crystal and preparation method thereof

Abstract

The invention relates to the technical field of functional oxide single crystal materials, and discloses a niobium-added strontium titanate single crystal and a preparation method thereof. The niobium-added strontium titanate single crystal is composed of a modified strontium titanate precursor, a niobium source dopant, an organic small molecule crystal growth regulator, a mineralizer, a flux and a lattice stabilizer, wherein the modified strontium titanate precursor is a coordination modified precursor system formed by a titanium source and a strontium source under the action of an organic carboxylic acid modifier; the small organic molecule crystal growth regulating agent is a nitrogen-containing heterocyclic ring small organic molecule. Through the synergistic effect of the modified precursor and the organic small molecule crystal growth regulating agent, uniform distribution of niobium in the strontium titanate single crystal is realized, and the single crystal nucleation and growth process is effectively regulated. On the premise of ensuring the stability of a strontium titanate main body lattice structure, the crystal integrity, the electrical property consistency and the process stability of the niobium-added strontium titanate single crystal are remarkably improved, and the method is suitable for preparing a high-quality functional oxide single crystal material.

Description

Technical Field

[0001] This invention relates to the field of functional oxide single crystal materials technology, specifically to a strontium titanate single crystal with niobium and its preparation method. Background Technology

[0002] Strontium titanate is a typical perovskite-structured functional oxide material. Due to its excellent dielectric and electrical properties, as well as good lattice matching with various functional oxide thin films, it is widely used in microelectronic devices, optoelectronic devices, sensors, and novel oxide electronics. By introducing donor elements into the strontium titanate lattice for doping, its carrier concentration and electrical transport behavior can be effectively controlled. Niobium-doped strontium titanate, in particular, has attracted widespread attention due to its significantly improved conductivity.

[0003] Currently, niobium-added strontium titanate materials can be prepared through both polycrystalline sintering and single-crystal growth. Single-crystal materials, due to the absence of grain boundary effects, exhibit significant advantages in electrical uniformity, carrier mobility, and device consistency, making them a crucial foundational material for high-end device applications. However, several technical challenges remain in the preparation of existing niobium-added strontium titanate single crystals: firstly, niobium is prone to uneven distribution or localized enrichment during crystal growth, affecting the overall stability of the single crystal's performance; secondly, defects such as oxygen vacancies and dislocations are easily introduced during crystal growth, leading to a decrease in crystal integrity and electrical performance.

[0004] Existing technologies mainly optimize the single crystal growth process by adjusting the ratio of inorganic raw materials, changing the sintering or growth temperature, and introducing mineralizers or fluxes. However, these methods are mostly focused on the control of macroscopic process parameters, with limited ability to control the microscopic nucleation and growth interface, making it difficult to effectively reduce defect density while ensuring high crystallization rate. Furthermore, existing reports rarely mention systematic optimization solutions for the strontium niobate titanate single crystal growth process from the perspective of precursor modification and synergistic regulation by organic small molecules.

[0005] Therefore, how to achieve uniform doping of niobium and improve the crystal integrity and electrical properties during single crystal growth without destroying the main crystal structure of strontium titanate remains a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0006] To overcome the technical challenges in the growth of niobium-added strontium titanate single crystals, such as poor niobium doping uniformity, high crystal defect density, and the difficulty in simultaneously achieving crystal integrity and electrical properties, the present invention aims to provide a niobium-added strontium titanate single crystal and its preparation method. This invention employs a modified strontium titanate precursor and introduces an organic small-molecule crystal growth regulator. Through the synergistic effect of a mineralizer, flux, and lattice stabilizer, the nucleation and growth process of the single crystal is controlled, thereby achieving a uniform distribution of niobium in the strontium titanate single crystal and promoting the formation of high-quality single crystals. This invention significantly improves the crystal integrity and electrical performance stability of niobium-added strontium titanate single crystals while ensuring the stability of the strontium titanate bulk lattice structure.

[0007] The objective of this invention can be achieved through the following technical solutions:

[0008] A niobium-added strontium titanate single crystal comprises the following raw materials in parts by weight: 80-95 parts of modified strontium titanate precursor; 0.5-5 parts of niobium source dopant; 0.05-2.0 parts of organic small molecule crystal growth regulator; 1-6 parts of mineralizer; 2-12 parts of flux; and 0.1-3 parts of lattice stabilizer. The modified strontium titanate precursor is a coordination-modified precursor system formed by titanium and strontium sources under the action of an organic carboxylic acid modifier. The organic small molecule crystal growth regulator is a nitrogen-containing heterocyclic organic small molecule that participates in regulating crystal nucleation and growth interface behavior during single crystal growth. Through the synergistic effect of the modified strontium titanate precursor and the organic small molecule crystal growth regulator, niobium is uniformly distributed in the strontium titanate single crystal, resulting in a niobium-added strontium titanate single crystal with improved crystal integrity and electrical properties.

[0009] Optionally, the modified strontium titanate precursor comprises the following raw materials in parts by weight: 45-55 parts of strontium carbonate; 35-45 parts of titanium dioxide; 3-8 parts of citric acid; and 10-25 parts of deionized water.

[0010] Optionally, the preparation method of the modified strontium titanate precursor includes the following steps:

[0011] (1) Strontium carbonate and titanium dioxide are added to a solvent and mixed to obtain a mixed system;

[0012] (2) Add citric acid to the mixed system to carry out the modification reaction and obtain the modified precursor system;

[0013] (3) The modified precursor system is processed to obtain the modified strontium titanate precursor.

[0014] Optionally, the mixing conditions in step (1) are to stir and mix at a speed of 300-600 r / min for 10-30 min at room temperature.

[0015] Optionally, the reaction conditions in step (2) are to carry out the reaction at 60-90°C for 1-3 hours, with continuous stirring during the reaction.

[0016] Optionally, the processing conditions in step (3) are drying at 80-120°C for 8-24 hours, followed by pre-firing at 600-900°C for 0.5-2 hours.

[0017] Optionally, the niobium source dopant is a niobium source system composed of niobium pentoxide and anhydrous ethanol in a mass ratio of 1:5 to 1:15; the mineralizing agent is composed of lithium fluoride and strontium chloride in a mass ratio of 1:1 to 1:3; the flux is composed of boric acid and lithium carbonate in a mass ratio of 2:1 to 5:1; and the lattice stabilizer is composed of magnesium oxide and aluminum oxide in a mass ratio of 1:1 to 1:4.

[0018] Optionally, a method for preparing a strontium titanate single crystal with niobium addition includes the following steps:

[0019] S1, the modified strontium titanate precursor is mixed with niobium source dopant, organic small molecule crystal growth regulator, mineralizer, flux and lattice stabilizer to obtain a single crystal growth raw material system;

[0020] S2, perform single crystal growth treatment on the single crystal growth raw material system to obtain strontium titanate single crystal with niobium.

[0021] Optionally, the reaction conditions for step S1 are to carry out the mixing treatment at room temperature to 60°C, with continuous stirring during the mixing process, and the mixing time is 30 to 120 minutes.

[0022] Optionally, the reaction conditions in step S2 are as follows: single crystal growth is performed at 900–1600°C, and after the single crystal growth is completed, cooling is performed under controlled cooling conditions, wherein the controlled cooling conditions are as follows: the temperature is reduced from the growth temperature to room temperature at a cooling rate of 0.5–10°C / min.

[0023] The beneficial effects of this invention are:

[0024] This invention constructs an organic carboxylic acid-coordination modified strontium titanate precursor and introduces nitrogen-containing heterocyclic organic small molecules as crystal growth regulators. This enables precise control of nucleation behavior and growth interface during single crystal growth, resulting in a more uniform distribution of niobium in the strontium titanate single crystal. It effectively suppresses the formation of structural defects such as oxygen vacancies and dislocations, thereby significantly improving the crystal integrity, carrier migration stability, and overall electrical performance consistency of niobium-added strontium titanate single crystals without changing the main crystal structure of strontium titanate. Attached Figure Description

[0025] The invention will now be further described with reference to the accompanying drawings.

[0026] Figure 1 A comparison of the infrared spectra of strontium titanate precursor and modified strontium titanate precursor;

[0027] Figure 2 This is a comparison chart of the performance test results of samples with different ratios. Detailed Implementation

[0028] The present invention will be further described below with reference to specific embodiments. However, the present invention is not limited to the following embodiments. Equivalent adjustments made without departing from the spirit and essence of the present invention should also be considered to fall within the protection scope of the present invention.

[0029] Example 1:

[0030] This embodiment aims to verify the feasibility and stability of the present invention in preparing strontium titanate single crystals with low additive dosage and mild process conditions, when all raw material components and reaction conditions are at the lower limit of the recommended range.

[0031] Preparation process

[0032] S1, Preparation of modified strontium titanate precursor

[0033] 45 parts of strontium carbonate and 35 parts of titanium dioxide were added to 10 parts of deionized water and stirred at 300 r / min for 10 min at room temperature to obtain a mixed system. 3 parts of citric acid were added to the mixed system and stirred continuously at 60 °C for 1 h to obtain a modified precursor system. The obtained modified precursor system was dried at 80 °C for 8 h and then pre-calcined at 600 °C for 0.5 h to obtain a modified strontium titanate precursor.

[0034] S2, Preparation of Strontium Niobate Titanate Single Crystals

[0035] Take 80 parts of the above-mentioned modified strontium titanate precursor and mix it with 0.5 parts of niobium source dopant (a mixture of niobium pentoxide and anhydrous ethanol in a mass ratio of 1:5), 0.05 parts of organic small molecule crystal growth regulator, 1 part of mineralizer (a mixture of lithium fluoride and strontium chloride in a mass ratio of 1:1), 2 parts of flux (a mixture of boric acid and lithium carbonate in a mass ratio of 2:1), and 0.1 parts of lattice stabilizer (a mixture of magnesium oxide and aluminum oxide in a mass ratio of 1:1). After mixing at room temperature for 30 min, the resulting single crystal growth raw material system is subjected to single crystal growth at 900℃. After growth, it is cooled to room temperature at a cooling rate of 0.5℃ / min to obtain niobium-added strontium titanate single crystal.

[0036] Example 2:

[0037] This embodiment aims to verify the comprehensive performance of the technical solution of the present invention in terms of crystal integrity, niobium doping uniformity, and process stability when the raw material components and reaction conditions are within the recommended median range, and serves as a preferred embodiment of the present invention.

[0038] Preparation process

[0039] S1, Preparation of modified strontium titanate precursor

[0040] 50 parts of strontium carbonate and 40 parts of titanium dioxide were added to 18 parts of deionized water and stirred at 450 r / min for 20 min at room temperature to obtain a mixed system. 5 parts of citric acid were added to the mixed system, and the mixture was stirred continuously at 75 °C for 2 h to obtain a modified precursor system. The obtained modified precursor system was dried at 100 °C for 16 h, followed by pre-calcination at 750 °C for 1 h to obtain a modified strontium titanate precursor. According to... Figure 1 A comparison of the infrared spectra before and after modification shows that the unmodified sample exhibits differences in infrared spectra at approximately 1470, 860, and 710 cm⁻¹. -1 The sample exhibits a distinct carbonate characteristic absorption peak at approximately 1590 cm⁻¹, indicating that strontium carbonate is a prominent component in the system, while organic-related absorption peaks are not obvious. In the modified sample, the intensity of the aforementioned carbonate characteristic peak is significantly reduced, and the peak intensity is also reduced at approximately 1590 cm⁻¹. -1 and 1400cm -1 The presence of carboxylate –COO in the vicinity enhanced the effect. - The characteristic absorption peak is located in the range of 1100–1200 cm⁻¹. -1 The presence of a distinct C–O stretching vibration absorption peak in the region indicates that citric acid has successfully undergone coordination modification with the strontium titanate precursor system. These changes demonstrate that the modification treatment effectively altered the chemical environment of the precursor, providing more uniform and stable precursor conditions for subsequent single crystal growth.

[0041] S2, Preparation of Strontium Niobate Titanate Single Crystals

[0042] Take 88 parts of the above-mentioned modified strontium titanate precursor and mix it with 2.5 parts of niobium source dopant (a mixture of niobium pentoxide and anhydrous ethanol in a mass ratio of 1:10), 0.8 parts of organic small molecule crystal growth regulator, 3.5 parts of mineralizer (a mixture of lithium fluoride and strontium chloride in a mass ratio of 1:2), 7 parts of flux (a mixture of boric acid and lithium carbonate in a mass ratio of 3:1), and 1.2 parts of lattice stabilizer (a mixture of magnesium oxide and aluminum oxide in a mass ratio of 1:2). After mixing at 40°C for 60 min, the resulting single crystal growth raw material system is subjected to single crystal growth at 1200°C. After growth, it is cooled to room temperature at a cooling rate of 5°C / min to obtain niobium-added strontium titanate single crystal.

[0043] Example 3:

[0044] This embodiment aims to verify the applicability and crystallization ability of the technical solution of the present invention under high additive dosage and high-temperature single crystal growth conditions when the raw material components and reaction conditions are at the upper limit of the recommended range.

[0045] Preparation process

[0046] S1, Preparation of modified strontium titanate precursor

[0047] 55 parts of strontium carbonate and 45 parts of titanium dioxide were added to 25 parts of deionized water and stirred at 600 r / min for 30 min at room temperature to obtain a mixed system. 8 parts of citric acid were added to the mixed system and the mixture was stirred continuously at 90 °C for 3 h to obtain a modified precursor system. The obtained modified precursor system was dried at 120 °C for 24 h and then pre-calcined at 900 °C for 2 h to obtain a modified strontium titanate precursor.

[0048] S2, Preparation of Strontium Niobate Titanate Single Crystals

[0049] Take 95 parts of the above-mentioned modified strontium titanate precursor, and mix it with 5 parts of niobium source dopant (niobium pentoxide and anhydrous ethanol at a mass ratio of 1:15), 2.0 parts of organic small molecule crystal growth regulator, 6 parts of mineralizer (lithium fluoride and strontium chloride at a mass ratio of 1:3), 12 parts of flux (boric acid and lithium carbonate at a mass ratio of 5:1), and 3 parts of lattice stabilizer (magnesium oxide and aluminum oxide at a mass ratio of 1:4). After mixing at 60°C for 120 min, the resulting single crystal growth raw material system is subjected to single crystal growth at 1600°C. After growth, it is cooled to room temperature at a cooling rate of 10°C / min to obtain niobium-added strontium titanate single crystal.

[0050] Comparative Example 1:

[0051] This comparative example examines the impact of using only a modified strontium titanate precursor without adding an organic small molecule crystal growth regulator on the crystallization integrity, niobium doping uniformity, and process stability of niobium-doped strontium titanate single crystals.

[0052] Preparation process

[0053] S1, Preparation of modified strontium titanate precursor

[0054] 50 parts of strontium carbonate and 40 parts of titanium dioxide were added to 18 parts of deionized water and stirred at 450 r / min for 20 min at room temperature to obtain a mixed system. 5 parts of citric acid were added to the mixed system and stirred continuously at 75 °C for 2 h to obtain a modified precursor system. The obtained modified precursor system was dried at 100 °C for 16 h and then pre-calcined at 750 °C for 1 h to obtain a modified strontium titanate precursor.

[0055] S2, Preparation of Strontium Niobate Titanate Single Crystals

[0056] Take 88 parts of the above-mentioned modified strontium titanate precursor, and mix it with 2.5 parts of niobium source dopant (niobium pentoxide and anhydrous ethanol in a mass ratio of 1:10), 0 parts of organic small molecule crystal growth regulator, 3.5 parts of mineralizer (lithium fluoride and strontium chloride in a mass ratio of 1:2), 7 parts of flux (boric acid and lithium carbonate in a mass ratio of 3:1), and 1.2 parts of lattice stabilizer (magnesium oxide and aluminum oxide in a mass ratio of 1:2). After mixing at 40°C for 60 min, the resulting single crystal growth raw material system is subjected to single crystal growth at 1200°C. After growth, it is cooled to room temperature at a cooling rate of 5°C / min to obtain niobium-added strontium titanate single crystal.

[0057] Comparative Example 2:

[0058] This comparative example aims to verify the effect of adding an organic small molecule crystal growth regulator on the crystallization integrity, niobium doping uniformity, and process stability of strontium titanate single crystals without using organic carboxylic acid modifiers to coordinate the strontium titanate precursor.

[0059] Preparation process

[0060] S1, Preparation of strontium titanate precursor

[0061] 50 parts of strontium carbonate and 40 parts of titanium dioxide were added to 18 parts of deionized water and stirred at 450 r / min for 20 min at room temperature to obtain a mixed system. The resulting mixed system was dried and then pre-calcined to obtain the strontium titanate precursor.

[0062] S2, Preparation of Strontium Niobate Titanate Single Crystals

[0063] Take 88 parts of the above-mentioned strontium titanate precursor and mix it with 2.5 parts of niobium source dopant (a mixture of niobium pentoxide and anhydrous ethanol in a mass ratio of 1:10), 0.8 parts of organic small molecule crystal growth regulator, 3.5 parts of mineralizer (a mixture of lithium fluoride and strontium chloride in a mass ratio of 1:2), 7 parts of flux (a mixture of boric acid and lithium carbonate in a mass ratio of 3:1), and 1.2 parts of lattice stabilizer (a mixture of magnesium oxide and aluminum oxide in a mass ratio of 1:2). After mixing at 40°C for 60 min, the resulting single crystal growth raw material system is subjected to single crystal growth at 1200°C. After growth, it is cooled to room temperature at a cooling rate of 5°C / min to obtain niobium-added strontium titanate single crystal.

[0064] Comparative Example 3:

[0065] This comparative example aims to verify the effects of neither organic carboxylic acid coordination modification of the strontium titanate precursor nor the addition of organic small molecule crystal growth regulators on the crystallization integrity, niobium doping uniformity, and process stability of niobium-doped strontium titanate single crystals.

[0066] Preparation process

[0067] S1, Preparation of strontium titanate precursor

[0068] 50 parts of strontium carbonate and 40 parts of titanium dioxide were added to 18 parts of deionized water and stirred at 450 r / min for 20 min at room temperature to obtain a mixed system. The resulting mixed system was dried and then pre-calcined to obtain the strontium titanate precursor.

[0069] S2, Preparation of Strontium Niobate Titanate Single Crystals

[0070] Take 88 parts of the above-mentioned strontium titanate precursor and mix it with 2.5 parts of niobium source dopant (a mixture of niobium pentoxide and anhydrous ethanol in a mass ratio of 1:10), 0 parts of organic small molecule crystal growth regulator, 3.5 parts of mineralizer (a mixture of lithium fluoride and strontium chloride in a mass ratio of 1:2), 7 parts of flux (a mixture of boric acid and lithium carbonate in a mass ratio of 3:1), and 1.2 parts of lattice stabilizer (a mixture of magnesium oxide and aluminum oxide in a mass ratio of 1:2). After mixing at 40°C for 60 min, the resulting single crystal growth raw material system is subjected to single crystal growth at 1200°C. After growth, it is cooled to room temperature at a cooling rate of 5°C / min to obtain niobium-added strontium titanate single crystal.

[0071] Performance testing:

[0072] 1. Single Crystal Integrity Test Method

[0073] Under the same equipment, operators, and batch conditions, multiple batches of single crystal growth experiments were conducted according to the preparation processes of Examples 1, 2, and 3, as well as Comparative Examples 1 to 3. After each batch of growth, the obtained crystals were screened by appearance, and crystals with obvious cracks, fractures, severe inclusions, or those unsuitable for further processing were removed. The number of complete single crystals obtained in each example and comparative example was counted. By comparing the complete single crystal production under multiple batch conditions in different examples and comparative examples, the impact of each technical solution on the single crystal formation integrity rate was evaluated.

[0074] 2. Single Crystal Size Consistency Test Method

[0075] The strontium titanate single crystals obtained in Examples 1, 2, and 3, as well as Comparative Examples 1 to 3, were processed according to the same cutting and sampling rules. The length, width, and thickness of each single crystal were measured, and the size distribution within the same batch and between different batches was recorded. By comparing the differences in size fluctuation range and consistency between the single crystals obtained in each example and the comparative examples, the stability and controllability of the single crystal growth process under different process conditions were evaluated.

[0076] 3. Electrical performance consistency test method

[0077] The single-crystal samples obtained in Examples 1, 2, and 3, and Comparative Examples 1 to 3, were processed into test pieces of the same specifications. Conventional electrical performance tests were conducted under consistent energizing conditions, and the response stability and performance fluctuations of different samples during the energizing process were recorded. By comparing the consistency of electrical responses at different locations within the same crystal and between different crystals, the differences in electrical performance uniformity and stability between the examples and comparative examples were evaluated.

[0078] 4. Test methods for process repeatability and batch-to-batch stability

[0079] Using the process parameters corresponding to Examples 1, 2, and 3, as well as Comparative Examples 1 to 3, multiple repeated preparations were conducted while maintaining consistent raw material sources, equipment conditions, and operating procedures. Changes in single crystal formation, appearance quality, and processability were recorded for each batch. The stability of different examples and comparative examples during multiple batch preparations was compared and analyzed to evaluate the process repeatability and batch-to-batch stability of each technical solution under actual production conditions.

[0080] Table 1 Comparison of performance test results of different embodiments and comparative examples.

[0081] Sample number Single crystal formation integrity rate (%) Single crystal size deviation rate (%) Percentage of samples with stable electrical properties (%) Qualification rate of multiple batches of crystallization (%) Example 1 82 6.5 80 78 Example 2 93 3.2 92 90 Example 3 86 5.1 85 83 Comparative Example 1 65 12.8 60 58 Comparative Example 2 58 16.5 52 50 Comparative Example 3 42 23.4 38 35

[0082] As shown in Table 1, the niobium-added strontium titanate single crystals prepared using the technical solution of this invention significantly outperformed the comparative samples in multiple engineering performance indicators. Among them, Example 2 showed the most outstanding performance in terms of single crystal integrity, reaching 93%, significantly higher than the 82% of Example 1 and 86% of Example 3, and also significantly better than the 65%, 58%, and 42% of comparative examples 1-3, respectively. These results indicate that the synergistic effect of the modified strontium titanate precursor and the organic small molecule crystal growth regulator is beneficial to improving the stability and integrity of the single crystal formation process.

[0083] Regarding the consistency of single crystal size, the size deviation rate of Example 2 was only 3.2%, significantly lower than 6.5% of Example 1 and 5.1% of Example 3, while the size deviation rate of the comparative samples was generally higher, reaching a maximum of 23.4%. This result indicates that under the median composition and process conditions used in Example 2, the single crystal growth process is more controllable, effectively reducing crystal size fluctuations and improving consistency within and between batches.

[0084] Regarding the stability of electrical performance, the proportion of stable samples in Example 2 reached 92%, which is significantly higher than 80% in Example 1 and 85% in Example 3, and much higher than 38%–60% in the comparative samples. This result further demonstrates that the present invention effectively improves the uniformity of the overall electrical performance of single crystals and reduces performance fluctuations between different crystals and different regions of the same crystal through precursor modification and synergistic regulation by small organic molecules.

[0085] Regarding process repeatability and batch-to-batch stability, Example 2 exhibited the highest crystallization yield of 90% in multiple batches of repeated preparation, while Examples 1 and 3 achieved 78% and 83%, respectively, both significantly better than the comparative samples' 35%–58%. This result demonstrates that the technical solution of this invention not only improves the crystallization quality of a single preparation but also exhibits good process stability and repeatability under repeated production conditions.

[0086] In summary, compared with the comparative examples, the embodiments of the present invention show significant advantages in terms of single crystal formation integrity, dimensional consistency, electrical performance stability, and process repeatability. Among them, Example 2 achieves the best level in all performance indicators, which fully demonstrates the effectiveness and superiority of the synergistic effect of the modified strontium titanate precursor and the organic small molecule crystal growth regulator, and provides a reliable technical approach for the stable preparation of high-quality niobium-added strontium titanate single crystals.

Claims

1. A strontium titanate single crystal with added niobium, characterized in that, The niobium-added strontium titanate single crystal comprises the following raw materials in parts by weight: 80-95 parts of modified strontium titanate precursor; 0.5-5 parts of niobium source dopant; 0.05-2.0 parts of organic small molecule crystal growth regulator; 1-6 parts of mineralizer; 2-12 parts of flux; and 0.1-3 parts of lattice stabilizer. The modified strontium titanate precursor is a coordination-modified precursor system formed by titanium and strontium sources under the action of an organic carboxylic acid modifier. The organic small molecule crystal growth regulator is a nitrogen-containing heterocyclic organic small molecule that participates in regulating crystal nucleation and growth interface behavior during single crystal growth. Through the synergistic effect of the modified strontium titanate precursor and the organic small molecule crystal growth regulator, niobium is uniformly distributed in the strontium titanate single crystal, resulting in a niobium-added strontium titanate single crystal with improved crystal integrity and electrical properties.

2. The strontium titanate single crystal with niobium addition according to claim 1, characterized in that, The modified strontium titanate precursor comprises the following raw materials in parts by weight: 45-55 parts strontium carbonate; 35-45 parts titanium dioxide; 3-8 parts citric acid; and 10-25 parts deionized water.

3. A strontium titanate single crystal with niobium addition according to claim 1 or 2, characterized in that, The preparation method of the modified strontium titanate precursor includes the following steps: (1) Strontium carbonate and titanium dioxide are added to a solvent and mixed to obtain a mixed system; (2) Add citric acid to the mixed system to carry out the modification reaction and obtain the modified precursor system; (3) The modified precursor system is processed to obtain the modified strontium titanate precursor.

4. A strontium titanate single crystal with niobium addition according to claim 3, characterized in that, The mixing conditions in step (1) are as follows: at room temperature, the mixture is stirred and mixed at a speed of 300-600 r / min for 10-30 min.

5. A strontium titanate single crystal with niobium addition according to claim 3, characterized in that, The reaction conditions for step (2) are as follows: the reaction is carried out at 60-90°C for 1-3 hours, and the mixture is continuously stirred during the reaction.

6. A strontium titanate single crystal with niobium addition according to claim 3, characterized in that, The processing conditions for step (3) are drying at 80-120℃ for 8-24 hours, followed by pre-firing at 600-900℃ for 0.5-2 hours.

7. A strontium titanate single crystal with niobium addition according to claim 1, characterized in that, The niobium source dopant is a niobium source system composed of niobium pentoxide and anhydrous ethanol in a mass ratio of 1:5 to 1:15; the mineralizing agent is composed of lithium fluoride and strontium chloride in a mass ratio of 1:1 to 1:3; the flux is composed of boric acid and lithium carbonate in a mass ratio of 2:1 to 5:1; and the lattice stabilizer is composed of magnesium oxide and aluminum oxide in a mass ratio of 1:1 to 1:

4.

8. A method for preparing a strontium titanate single crystal with niobium, wherein the strontium titanate single crystal with niobium is as described in any one of claims 1 to 7, characterized in that, Includes the following steps: S1, the modified strontium titanate precursor is mixed with niobium source dopant, organic small molecule crystal growth regulator, mineralizer, flux and lattice stabilizer to obtain a single crystal growth raw material system; S2, perform single crystal growth treatment on the single crystal growth raw material system to obtain strontium titanate single crystal with niobium.

9. The method for preparing a strontium titanate single crystal with niobium according to claim 8, characterized in that, The reaction conditions for step S1 are as follows: mixing is carried out at room temperature to 60°C, with continuous stirring during the mixing process, and the mixing time is 30 to 120 minutes.

10. The method for preparing a strontium titanate single crystal with niobium according to claim 8, characterized in that, The reaction conditions for step S2 are as follows: single crystal growth is performed at 900–1600°C, and after the single crystal growth is completed, cooling is performed under controlled cooling conditions, wherein the controlled cooling conditions are as follows: the temperature is reduced from the growth temperature to room temperature at a cooling rate of 0.5–10°C / min.

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