DOPED PbTiO3 PEROVSKITE SINGLE CRYSTAL SEED AND METHOD FOR MANUFACTURING THE SAME

Abstract

To provide a doped PbTiO3 perovskite single crystal seed, and a method for manufacturing the same.SOLUTION: An doped perovskite single crystal seed containing Pb, Bi and Ti has a (PbBix)TiO3 composition. (where, 0.01≤x≤0.1 is satisfied.)SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a doped PbTiO3 perovskite single crystal seed and a method for manufacturing the same.

Background Art

[0002] A piezoelectric element is an element that can convert mechanical energy into electrical energy or, conversely, apply electrical energy to the piezoelectric element to convert it into mechanical energy.

[0003] Due to excellent piezoelectric properties, piezoelectric elements are widely applied as functional devices such as transformers, actuators, transducers, sensors, resonators, and filters.

[0004] In particular, recently, the demand for transparent piezoelectric elements has been increasing.

[0005] Transparent piezoelectric elements are future IT elements applicable to information recognition components such as transparent sensors, transparent RFID tags, and transparent security electronic devices, information processing components such as transparent digital / analog ICs, and information display components such as smart windows and transparent information displays.

[0006] As piezoelectric elements, a perovskite structure is generally most widely used.

[0007] In particular, the composition of the Pb(Zr,Ti)O3 (PZT) series, which is a solid solution of PbZrO3 (PZ) and PbTiO3 (PT) mainly composed of lead, is most widely used as a dielectric and piezoelectric material due to its high dielectric constant and low dielectric loss characteristics.

[0008] However, recently, as the piezoelectric properties required for piezoelectric elements have become increasingly high, various studies have been conducted to improve the general piezoelectric ceramic materials of the PZT series to enhance the piezoelectric properties.

[0009] Among the above-mentioned studies, the TGG (Templated Grain Growth) method, which is one of the most promising methods, as shown in Fig. 1, is a method of growing polycrystalline powder with orientation by utilizing seeds in the form of a template having high orientation.

[0010] It is known that the piezoelectric properties of polycrystalline ceramics manufactured by orientation growth in the TGG method increase significantly by orientation growth compared to the piezoelectric properties of non-oriented polycrystalline piezoelectric ceramics.

[0011] However, in order to apply the TGG method, it is necessary to previously develop seeds having high orientation while having a composition similar to that of the polycrystalline powder for seed growth.

[0012] In particular, when the seeds are single crystals, the polycrystals oriented by the TGG method come to have substantially the same or similar crystallographic directions to each other.

[0013] In order to manufacture seeds in the form of a template, conventionally, a topochemical process applying a kind of multi-step substitution method in a method of growing two-dimensional seeds has been utilized.

[0014] The topochemical process is a method of first creating an intermediate in a two-dimensional shape and then creating a perovskite structure first by substitution of the component elements of the intermediate.

[0015] Although it may be advantageous to use PZ, PT or PZT seeds as seeds for TGG in PZT series piezoelectric materials, such seeds are known to be difficult to manufacture, and conventionally, BaTiO3 (BT) seeds were manufactured by a topochemical process and used as seeds for TGG.

[0016] Recently, there has been a case where the manufacture of seeds having a composition of (Na,Bi,Pb)TiO3 (NBPT) similar to PT was successfully carried out by a topochemical process. First, PbBi4Ti4O 15It was manufactured by synthesizing a plate-like composition and replacing the elements constituting the composition with other nuclide elements to convert it into a perovskite structure of the NBPT composition. The reason why the NBPT composition was manufactured without using PbTiO3 seeds in the topochemical process is that it is difficult to manufacture PT seeds even in the topochemical process.

[0017] Since the intermediate has a layered structure in the topochemical process, the topochemical process has an advantage in thermodynamically maintaining a two-dimensional shape.

[0018] In particular, since the perovskite structure is known to be difficult to have a two-dimensional shape in terms of thermodynamic energy, the topochemical process has been mainly used.

[0019] However, the topochemical process has problems such as requiring a multi-step process and multiple heat treatment steps, resulting in increased costs, and thus it cannot be commercialized in terms of time and cost. Therefore, if PT seeds can be manufactured by the molten salt method, which is a relatively simple one-step process, it can be said to be advantageous for commercialization.

[0020] In particular, the seeds manufactured by the topochemical process are advantageous for being manufactured in a template form, but have the disadvantage of not being single crystals. On the other hand, if seeds are manufactured by the molten salt method, which is a simple one-step process, there is an advantage that single crystal seeds are generally manufactured.

[0021] When the seeds are manufactured in a polycrystalline state, crystal grains having different piezoelectric properties are mixed, so it is difficult to control the crystal grains having the most excellent directionality. However, single crystal seeds are crystal grains having excellent directionality and are easy to control.

[0022] In addition, single crystal seeds are basically transparent, and transparent piezoelectric devices can be manufactured. By combining with polymers due to the excellent piezoelectric properties unique to single crystals, flexible piezoelectric products with excellent piezoelectric properties can be manufactured.

[0023] To maximize the advantages of single crystal seeds, there is a need for a method of manufacturing a PT perovskite seed that can have a cross-sectional shape perpendicular to at least one axial direction constituting a rectangular coordinate system, and further perpendicular to all three axial directions, particularly for perovskites having a cubic (tetrahedral) crystal structure.

[0024] However, it is known that single-crystal PT of a size large enough to be used as an element is extremely difficult to manufacture, so difficult that it has never been reported until now.

Summary of the Invention

Problems to be Solved by the Invention

[0025] An object of the present invention is to provide a doped PT perovskite single crystal seed having a new composition with excellent orientation.

[0026] More specifically, an object of the present invention is to provide a PT perovskite single crystal seed that can have a cross-sectional shape perpendicular to at least one axial direction constituting a rectangular coordinate system, and further perpendicular to all axial directions constituting the rectangular coordinate system.

[0027] Another object of the present invention is to provide a method for manufacturing a doped PT perovskite single crystal seed that can manufacture the doped PT perovskite single crystal seed in one - step using relatively simple processes.

[0028] The objects of the present invention are not limited to the objects mentioned above, and other objects and advantages of the present invention not mentioned should be understandable from the following description and should be more clearly understandable from the examples of the present invention. Also, it can be easily understood that the objects and advantages of the present invention can be realized by the means shown in the claims and their combinations.

Means for Solving the Problems

[0029] The doped PT perovskite single crystal seed according to one embodiment of the present invention contains Pb, Bi, and Ti, and may be a doped perovskite single crystal seed having a composition of (PbBi x )TiO3. (However, 0.01 ≦ x ≦ 0.1.)

[0030] The doped PbTiO3 perovskite single crystal seed according to another embodiment of the present invention contains Pb, Bi, Ti, and Mg, and may be a doped perovskite single crystal seed having a composition of (PbBi x Mg y )TiO3. (However, 0.01 ≦ x ≦ 0.1, 0.001 ≦ y ≦ 0.03.)

[0031] The method for manufacturing a doped PT perovskite single crystal seed according to the present invention may include: (a) mixing a powder for a doped PT perovskite single crystal seed containing 100 at.% of a Pb compound, 1 to 10 at.% of a Bi compound, and 100 at.% of a Ti compound; (b) drying the mixture for the single crystal seed; (c) firing the dried mixture for the single crystal seed; (d) milling the fired and doped PT; (e) charging the fired and doped PT and a salt into a crucible and then performing heat treatment; and (f) removing the remaining salt.

Advantages of the Invention

[0032] In the present invention, a doped PT perovskite single crystal seed having a new composition can be provided.

[0033] Further, the doped PT perovskite single crystal seed having the above new composition of the present invention can provide the effect of improving the piezoelectric characteristics of the final perovskite element by having a rectangular cross section when observed in the three axial directions of the orthogonal coordinate system.

[0034] In addition, the present invention can provide a method for manufacturing a doped PT perovskite single crystal seed that is very simple yet excellent in orientation and piezoelectric properties.

[0035] Together with the above-described effects, the specific effects of the present invention will be described together while explaining the specific matters for implementing the following invention.

Brief Description of the Drawings

[0036]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Modes for Carrying Out the Invention

[0037] The above-mentioned objects, features and advantages will be described in detail below with reference to the accompanying drawings, whereby those having ordinary knowledge in the technical field to which the present invention pertains should be able to easily implement the technical idea of the present invention. When explaining the present invention, if it is determined that a specific description of the known technology related to the present invention may unnecessarily obscure the gist of the present invention, the detailed description will be omitted. Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the drawings, the same reference numerals are used to indicate the same or similar components.

[0038] Hereinafter, when it is said that any configuration is arranged “above (or below)” a component or “on (or under)” a component, it can be meant that not only is any configuration arranged in contact with the upper surface (or lower surface) of the component, but other configurations can be interposed between the component and any configuration arranged on (or under) the component.

[0039] Also, when it is described that a certain component is “connected,” “coupled,” or “joined” to another component, it should be understood that the components may be directly connected or joined to each other, or other components may be “interposed” between the components, or each component may be “connected,” “coupled,” or “joined” through other components.

[0040] Hereinafter, a perovskite single crystal seed according to some embodiments of the present invention and a method for manufacturing the same will be described.

[0041] In the molten salt process, the fired powder and the salt are heat-treated at a temperature equal to or higher than the temperature at which the salt melts, so that a part of the fired powder grows to form a seed.

[0042] The molten salt process is a relatively simple one-step method, but the composition conditions for growth on the seed are very strict and it cannot be utilized relatively widely.

[0043] In the present invention, an attempt is made to manufacture a PT-based perovskite single crystal seed doped in a relatively simple manner through the molten salt process.

[0044] The present invention sets the composition by adjusting the Bi content as a dopant in order to form a single crystal seed of doped PT perovskite ceramics.

[0045] In particular, in the present invention, (PbBi x)When the Bi content (composition range) is changed in the [[ID=]])TiO3(0.01 ≦ x ≦ 0.1) composition, it was confirmed that a single-crystal seed having a cross-section perpendicular to the three axes of the rectangular coordinate system is generated only at a specific Bi content.

[0046] When x is 0, Bi is not added and it has an irregular shape, and thus, a powder that cannot be utilized as a single-crystal seed is produced.

[0047] On the other hand, when x deviates from the above-mentioned range, an irregular-shaped powder is produced due to the excessive addition of Bi.

[0048] In other words, when Bi is not added from the beginning in the seed composition, or conversely, when the Bi content is added above a specific value, an irregular-shaped powder that cannot be utilized as a seed is produced.

[0049] Figure 2 is a flowchart showing a method for manufacturing a doped PT-based perovskite single-crystal seed of the present invention.

[0050] As shown in Figure 2, the method for manufacturing a doped PT perovskite single-crystal seed of the present invention includes a step of mixing powders for a doped PT perovskite single-crystal seed, a step of drying the mixture for the single-crystal seed, a step of firing the dried mixed water for the seed, a step of milling the fired and doped PT, a step of charging the fired and doped PT into a crucible after firing with a salt and then performing heat treatment, and a step of removing the remaining salt.

[0051] First, prepare a mixture for a doped PT perovskite seed and a salt.

[0052] To prepare the mixture for the doped PT perovskite seed, a step of mixing precursors including a Pb-containing compound, a Bi-containing compound, and a Ti-containing compound is performed.

[0053] The step of mixing the precursors is to weigh the precursors containing the compound according to the composition ratio so as to have a composition for doped PT perovskite seeds. The Bi-containing compound, Pb-containing compound, and Ti-containing compound contain 1-10 at.%, 100 at.%, and 100 at.%, respectively, and can be mixed by wet milling.

[0054] At this time, the solvent does not need to be particularly limited, and distilled water, alcohol, propanol, etc. may be used.

[0055] As a non-limiting and specific example, the Bi-containing compound may be Bi2O3, the Pb-containing compound may be PbO, and the Ti-containing compound may be TiO2.

[0056] In addition to the compounds presented above, other substances may be used as needed for the Bi-containing compound, Pb-containing compound, and Ti-containing compound.

[0057] As a non-limiting and specific example of the mixing process using the wet milling, a ball mill can be used to mix the precursors for 0.5-72 hours. The precursor mixing time is sufficient as long as the precursors can be sufficiently mixed.

[0058] Thereafter, the mixed precursors can be dried in a dry oven.

[0059] The dried precursors are fired by a firing process.

[0060] As a non-limiting and specific example of the firing process, it can be fired at 600-900 °C for 0.5-5 hours.

[0061] The fired precursor can be further milled via a ball mill within 72 hours if necessary. In other words, the fired precursor can be unmilled or, if milled, milled for a milling time within 72 hours.

[0062] Thereafter, the doped PT perovskite seed mixture and the salt are charged into a crucible and then heat-treated.

[0063] As a non-limiting and specific example, the salt may include one or more of KF and KCl.

[0064] Based on 100% by weight of the total of the doped PT perovskite seed mixture and the salt, the salt may be mixed at 30 - 70% by weight.

[0065] When the content of the salt is less than 30% by weight, liquid phase formation may be insufficient, and it may be difficult to sufficiently wet the fired powder during the heat treatment process.

[0066] Conversely, when the content of the salt exceeds 70% by weight, there is a risk of interfering with the contact between the fired powders.

[0067] Next, the mixed mixture is heat-treated to produce a Pb-based perovskite seed having a composition of (PbBi x )TiO3. Here, 0.01 ≦ x ≦ 0.1.

[0068] The heat treatment may be carried out at 800 - 900 °C for 0 - 10 hours.

[0069] The 0 hours refers to the time set in the heat treatment equipment, which means a heat treatment process carried out in a state where, after the heat treatment equipment reaches the heat treatment temperature, the temperature immediately drops without a holding time.

[0070] When the heat treatment temperature is less than 800 °C, the liquid phase formation of the molten salt may be insufficient, and crystal growth may also be insufficient.

[0071] Conversely, when the heat treatment temperature exceeds 900 °C, the growth of the seed is not efficient compared to the increased energy required for the heat treatment.

[0072] Next, the Pb-based seed is washed to remove the remaining salts.

[0073] The removal of the non-limiting and specific remaining salts may be performed by a method in which the salts cooled after the heat treatment are acid-treated with water and about 60% nitric acid solution at 50 - 85 °C and then washed with distilled water.

[0074] In the process of removing the salts, the remaining salts can be removed by being selectively dissolved in distilled water during the washing process with distilled water after reacting with the acid.

[0075] The washing may be performed at least once or more, and may be performed in various ways such as filtering, centrifugation, and stirring.

[0076] The doped PT perovskite single crystal seed produced by the manufacturing method in the present invention is (PbBi x )TiO3 (0.01 ≦ x ≦ 0.1).

[0077] The final product, the doped PT perovskite single crystal seed, has a perovskite (ABO3) structure, with Pb and Bi located at the A position and Ti located at the B position.

[0078] The doped PT perovskite seed of the present invention may have a tetragonal crystal structure.

[0079] In particular, depending on the content (composition range) of the dopant, the doped PT perovskite single crystal seed of the present invention may have a completely flat rectangular shape with respect to the three axial directions constituting the coordinate system.

[0080] For example, a cross-section perpendicular to the x-axis, y-axis, or z-axis direction shows a flat rectangular shape.

[0081] Specific examples of the above-described doped PT perovskite single crystal seed and its manufacturing method are as follows.

[0082] 1. Manufacture of Pb-based perovskite seed

[0083] <Example 1: Manufacture of perovskite single crystal seed having (PbBi 0.01 )TiO3 composition>

[0084] Using Bi2O3 as the Bi-containing compound, PbO as the Pb-containing compound, and TiO2 as the Ti-containing compound, the weights of the respective component powders used to manufacture the single crystal seed of Example 1 are 223.199 g of PbO, 2.329785 g of Bi2O3, and 79.865 g of TiO2, and the element ratio of each constituent component Bi:Pb:Ti constituting the seed is 0.01:1:1.

[0085] The PbO + TiO2 + B2O3 mixed powder was mixed using a ball mill for 24 hours and then dried in a dry oven.

[0086] The dried mixed powder was fired at 700 °C for 2 hours to form (PbBi 0.01 )TiO3 perovskite.

[0087] The fired (PbBi 0.01 )TiO3 perovskite powder was further pulverized and mixed using a ball mill for 24 hours.

[0088] The salt (KF or KF + KCl) and the (PbBi 0.01 )TiO3 perovskite powder were charged into an Al2O3 crucible and then heat-treated at 850 °C for 1 hour.

[0089] The heat-treated (PbBi 0.01)The TiO3 perovskite powder was washed with water at 80°C using a stirrer in a mixture of water and nitric acid with a purity of 60% (water:nitric acid = 4:1) under the condition of 300 rpm.

[0090] <Example 2: Production of a perovskite single crystal seed having a (PbBi 0.05 )TiO3 composition>

[0091] The weights of the component powders used to produce the single crystal seed of Example 2 were 223.199 g of PbO, 11.64893 g of Bi2O3, and 79.865 g of TiO2. The single crystal seed of Example 2 was produced under the same conditions as Example 1 except that the elemental ratio of each constituent component Bi:Pb:Ti constituting the seed was 0.05:1:1.

[0092] <Example 3: Production of a perovskite single crystal seed having a (PbBi 0.10 )TiO3 composition>

[0093] The weights of the component powders used to produce the single crystal seed of Example 3 were 223.199 g of PbO, 23.29785 g of Bi2O3, and 79.865 g of TiO2. The single crystal seed of Example 3 was produced under the same conditions as Example 1 except that the elemental ratio of each constituent component Bi:Pb:Ti constituting the seed was 0.10:1:1.

[0094] <Example 4: Production of a perovskite single crystal seed having a (PbBi 0.05 )TiO3 composition>

[0095] The single crystal seed of Example 4 was produced under the same conditions as Example 2 except that an MgO crucible was used when compared with Example 2.

[0096] <Comparative Example 1: Production of a perovskite seed having a PbTiO3 composition>

[0097] The weight of each component powder used to produce the single crystal seed of Comparative Example 1 was 223.199 g, TiO2 was 79.865 g, and the elemental ratio of each constituent component Bi:Pb:Ti constituting the seed was 0:1:1. Except for this, the single crystal seed of Comparative Example 1 was produced under the same conditions as in Example 1 above.

[0098] <Comparative Example 2: (PbBi 0.20 ) Production of perovskite seed having TiO3 composition>

[0099] The weight of each component powder used to produce the single crystal seed of Comparative Example 2 was 223.199 g, Bi2O3 was 46.5957 g, and TiO2 was 79.865 g. Except that the elemental ratio of each constituent component Bi:Pb:Ti constituting the seed was 0.20:1:1, the single crystal seed of Comparative Example 2 was produced under the same conditions as in Comparative Example 1 above.

[0100] Figure 3 is an SEM image of the seeds produced in Examples 1 to 3 of the present invention and Comparative Examples 1 and 2.

[0101] As shown in Figure 3, it can be seen that the cross-sections perpendicular to the three axes of the seed orthogonal coordinate system in Examples 1 to 3 of the present invention all have a flat shape.

[0102] On the other hand, it was observed that the seeds of Comparative Examples 1 and 2 of the present invention are flat with respect to only one axis of the orthogonal coordinate system or have a shape that is not flat with respect to any axis of the orthogonal coordinate system.

[0103] The results of Examples 1 to 3 of the present invention are presumed to be because abnormal grain growth occurred in which grain growth in a specific orientation was more dominant than grain growth in other orientations.

[0104] In other words, when comparing Examples 1 to 3 of the present invention and Comparative Examples 1 and 2, by substituting Bi for Pb in excess in a partial composition range region as a donor, Bi (0.01~0.1)The perovskite seeds with a PbTiO3 composition are judged to have promoted abnormal particle growth and formed seeds in single crystal form.

[0105] Figure 4 is an SEM image of single crystal seeds of Example 2 (Al2O3 crucible) and Example 4 (MgO crucible) of the present invention.

[0106] It can be seen that both Example 2 and Example 4 of the present invention have a completely flat shape in the cross section perpendicular to the three axes of the rectangular coordinate system.

[0107] However, it can be confirmed that the single crystal seeds of Example 4 have a cleaner surface without adsorption or adhesion of other fine crystals on the surface after being washed with water compared to Example 2.

[0108] The results in Figure 4 suggest that excellent surface characteristics of the single crystal seeds of the present invention can be obtained by adding Mg.

[0109] <Example 5: (PbBi 0.05 Mg 0.001 ) Preparation of perovskite single crystal seeds having a TiO3 composition>

[0110] The weights of the respective component powders used to produce the single crystal seeds of Example 5 are 223.199 g of PbO, 11.64893 g of Bi2O3, 79.865 g of TiO2, and 0.040304 g of Mg. The single crystal seeds of Example 5 were produced under the same conditions as Example 1 except that the elemental ratio of each constituent component Bi:Pb:Mg:Ti constituting the seeds is 0.05:1:0.001:1.

[0111] <Example 6: (PbBi 0.05 Mg 0.01 ) Preparation of perovskite single crystal seeds having a TiO3 composition>

[0112] The weights of the component powders used to produce the single crystal seed of Example 6 were 223.199 g of PbO, 11.64893 g of Bi2O3, 79.865 g of TiO2, and 0.40304 g of MgO. The single crystal seed of Example 6 was produced under the same conditions as Example 1, except that the elemental ratio of each constituent component Bi:Pb:Mg:Ti constituting the seed was 0.05:1:0.01:1.

[0113] <Example 7: (PbBi 0.05 Mg 0.03 )TiO3 Composition Perovskite Single Crystal Seed Production>

[0114] The weights of the component powders used to produce the single crystal seed of Example 7 were 223.199 g of PbO, 11.64893 g of Bi2O3, 79.865 g of TiO2, and 1.20912 g of MgO. The single crystal seed of Example 7 was produced under the same conditions as Example 1, except that the elemental ratio of each constituent component Bi:Pb:Mg:Ti constituting the seed was 0.05:1:0.03:1.

[0115] <Comparative Example 3: (PbBi 0.05 Mg 0.05 )TiO3 Composition Perovskite Seed Production>

[0116] The weights of the component powders used to produce the single crystal seed of Comparative Example 3 were 223.199 g of PbO, 11.64893 g of Bi2O3, 79.865 g of TiO2, and 2.0152 g of MgO. The single crystal seed of Comparative Example 3 was produced under the same conditions as Example 1, except that the elemental ratio of each constituent component Bi:Pb:Mg:Ti constituting the seed was 0.05:1:0.05:1.

[0117] Figure 5 is an SEM image of the seeds of Example 2, Examples 5 to 7, and Comparative Example 3 of the present invention.

[0118] As presented in Figure 5, it can be seen that the seeds of Example 2, Examples 5 to 7 of the present invention are all single crystal seeds having a shape with a flat cross section perpendicular to all three axes of the rectangular coordinate system.

[0119] However, it can be confirmed that the seeds of Examples 5 to 7 of the present invention have a clean surface without adsorption or adhesion of other fine crystals on the surface after washing, as compared with the seeds of Example 2.

[0120] On the other hand, it can be seen that when 5 at.% of Mg is added to the seed of Comparative Example 3 of the present invention, not only is the single crystal seed itself not formed, but also a seed with a cross-section perpendicular to any one axis of the rectangular coordinate system is not formed.

[0121] Figure 6 is the XRD and SEM observation results of a perovskite single crystal seed having a (PbBi 0.04 Mg 0.01 )TiO3 composition.

[0122] As shown in Figure 6, it can be seen that the perovskite single crystal seed having the composition manufactured in the present invention has a cubic (tetragonal) crystal structure from the XRD results, does not contain other secondary phases, and is furthermore a single crystal.

[0123] Therefore, when perovskite grows in a subsequent process on the rectangular single crystal seed manufactured in the example of the present invention, the growth is more likely to continue only when the subsequent perovskite components are aligned in a specific direction on the rectangular single crystal seed.

[0124] In particular, when the single crystal seed of the present invention is applied to a process such as TGG having particle orientation, the crystal grains grown in a specific orientation of the single crystal seed of the present invention in a subsequent process have substantially the same orientation between the crystal grains, so that the final product can exhibit piezoelectric characteristics identical or similar to those of a single crystal even though it is a polycrystal.

[0125] As described above, the present invention has been described with reference to the drawings illustrated for the present invention. However, the present invention is not limited by the embodiments and drawings disclosed in this specification, and it is obvious that various modifications can be made by those skilled in the art within the scope of the technical idea of the present invention. In addition, even if the effects of the configuration of the present invention are not explicitly described while explaining the above-described embodiments of the present invention, it is natural that the effects predictable by the configuration should also be recognized.

Claims

1. containing Pb, Bi, and Ti, (PbBi ｘ )TiO ３ doped perovskite single crystal seed having the composition. (However, 0.01 ≦ x ≦ 0.1.)

2. The seed is a doped perovskite single crystal seed according to claim 1, wherein the cross-sections perpendicular to the three axial directions constituting the orthogonal coordinate system have a rectangular shape.

3. The seed is a doped perovskite single crystal seed according to claim 1, wherein the cross-sections perpendicular to the three axial directions constituting the orthogonal coordinate system all have a flat shape.

4. The seed is a doped perovskite single crystal seed according to claim 1, having a tetragonal crystal structure and containing no other secondary phase.

5. The seed further contains Mg, (PbBi ｘ Mg ｙ )TiO ３ The doped perovskite single crystal seed according to claim 1, having a composition of (where 0.01 ≦ x ≦ 0.1 and 0.001 ≦ y ≦ 0.03).

6. (a) A doped PbTiO containing 100 at.% of a Pb compound, 1 to 10 at.% of a Bi compound, and 100 at.% of a Ti compound ３ Mixing a powder for a perovskite single crystal seed; (b) drying the mixture for the single crystal seed; (c) firing the dried mixture for the single crystal seed; (d) milling the fired and doped PbTiO ３ ; (e) A step of loading into a crucible and then heat-treating the salt and fired and doped PbTiO ３ ; and (f) removing the remaining salt; A method for manufacturing a doped perovskite single crystal seed, comprising:

7. further containing a Mg compound additionally in the step (a), The ratio of the Pb compound to the Mg compound is (100) at. %:(0.1-3) at. %, A method for manufacturing a doped perovskite single crystal seed according to claim 6.

8. In the step (c), the firing process is maintained at a temperature condition of 600 to 900° C. for 0.5 to 5 hours, A method for manufacturing a doped perovskite single crystal seed according to claim 6.

9. In the step (e), the heat treatment process is maintained at a temperature condition of 800 to 900° C. for 0 to 10 hours, A method for manufacturing a doped perovskite single crystal seed according to claim 6.

10. In the step (e), the salt is KF or a mixture of KF and KCl, Based on 100% by weight of the total of the perovskite single crystal seed composition and the salt, the alkaline salt is mixed at 30 to 70% by weight, A method for manufacturing a doped perovskite single crystal seed according to claim 6.

11. A piezoelectric element comprising a perovskite oriented on the perovskite seed according to any one of claims 1 to 5.

12. A functional element comprising the piezoelectric element according to claim 11.

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