Sputtering target material and sputtering target

Abstract

To provide a sputtering target material excellent in characteristics.SOLUTION: A sputtering target material is composed of a sintered body of an oxide including potassium, sodium, niobium, and oxygen. A number average particle diameter Nd and an area average particle diameter Nv in a plurality of crystal grains observed on a sputter surface satisfy a relational expression (Nv-Nd) / Nd≤2.1, or the area average particle diameter Nv and an area average standard deviation Ns satisfy a relational expression Ns / Nv≤0.76.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a sputtering target material and a sputtering target.

Background Art

[0002] When forming a piezoelectric thin film, a sputtering target material (hereinafter referred to as a KNN target material or simply a target material) made of a sintered body of an oxide containing potassium, sodium, niobium, and oxygen may be used (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] An object of the present disclosure is to improve the characteristics of a KNN target material.

Means for Solving the Problems

[0005] According to one aspect of the present disclosure, a sputtering target material made of a sintered body of an oxide containing potassium, sodium, niobium, and oxygen, wherein the number average particle diameter Nd and the area average particle diameter Nv in a plurality of crystal grains observed on the sputtering surface satisfy the relational expression (Nv - Nd) / Nd ≤ 2.1, a sputtering target material is provided.

[0006] According to another aspect of the present disclosure, a sputtering target material made of a sintered body of an oxide containing potassium, sodium, niobium, and oxygen, The area-average particle diameter Nv and area-average standard deviation Ns of multiple crystal grains observed on the sputtered surface satisfy the relationship Ns / Nv ≤ 0.76. A sputtering target material is provided.

[0007] According to yet another aspect of this disclosure, A sputtering target material according to any of the above embodiments, A backing plate bonded to the sputtering target material, A sputtering target is provided that includes the following features. [Effects of the Invention]

[0008] According to this disclosure, it is possible to improve the properties of KNN target material. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 shows one embodiment of the target material 10 of this disclosure. [Figure 2] Figure 2 is a diagram illustrating the manufacturing flow of the target material 10 of this disclosure. [Figure 3] Figure 3 is a schematic diagram of the sintering apparatus 100 used in this disclosure. [Modes for carrying out the invention]

[0010] <One aspect of this disclosure> The following describes one aspect of this disclosure, primarily with reference to Figures 1 to 3.

[0011] (1) Composition of the target material In this embodiment, the target material 10 is mainly composed of a sintered body containing an oxide (alkali niobium oxide) containing potassium (K), sodium (Na), niobium (Nb), and oxygen (O), i.e., a KNN sintered body. The crystal grains that mainly constitute the KNN sintered body have a perovskite structure. Specifically, the KNN sintered body has a composition formula (K 1-xNa x ) It is represented by NbO3(0 < x < 1), and the coefficient x [= Na / (K + Na)] in the above compositional formula satisfies 0 < x < 1, preferably 0.4 ≤ x ≤ 0.8. The KNN sintered body constituting the target material 10 of this embodiment is substantially an oxide sintered body composed of potassium, sodium, niobium and oxygen, or an oxide sintered body further containing a dopant element shown below. Here, "substantially" means that 99% or more of all the atoms constituting the KNN sintered body are composed of potassium, sodium, niobium and oxygen, or when the KNN sintered body contains a dopant element, it means that it is composed of potassium, sodium, niobium, oxygen and the dopant element.

[0012] The composition ((K + Na) / Nb) of K, Na, and Nb in the target material 10 satisfies the relationship of 0.90 or more and 1.25 or less, more preferably 0.95 or more and 1.20 or less, and still more preferably 1.00 or more and 1.10 or less. Here, K, Na, and Nb in the formula of (K + Na) / Nb are the numbers of K atoms, Na atoms, and Nb atoms contained in the KNN sintered body, respectively. Although the composition ratio of the target material 10 can be estimated from the charged amount of the raw material, it can also be measured by a known method. For example, it can be determined by an inductively coupled plasma atomic emission spectrometer (ICP - AES, such as SPS5000 manufactured by Seiko Instruments Inc., etc.).

[0013] The target material 10 may contain at least one element (dopant) selected from the group shown below, for example, at a concentration of 5 at% or less. Examples of dopants include: lithium (Li), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), bismuth (Bi), antimony (Sb), vanadium (V), indium (In), tantalum (Ta), molybdenum (Mo), tungsten (W), chromium (Cr), titanium (Ti), zirconium (Zr), hafnium (Hf), scandium (Sc), yttrium (Y), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), samarium ( Examples include at least one element selected from the group consisting of Sm, europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu), copper (Cu), zinc (Zn), silver (Ag), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), aluminum (Al), silicon (Si), germanium (Ge), tin (Sn), and gallium (Ga). If multiple of the above elements are present, the total concentration is 5 at% or less, and the amount of dopant added is usually 0.1 at% or more.

[0014] The target material 10 is, for example, molded into a disc shape and joined (attached) to a backing plate (cooling plate) (not shown) made of Cu or the like via a bonding material such as In, Sn, and alloys containing these metals, and is used as a sputtering target. Of the two main surfaces of the target material 10, the surface different from the surface joined to the cooling plate is used as the surface exposed to plasma such as argon (Ar) during the film formation process, i.e., the sputtering surface 10s that emits atoms constituting the film.

[0015] When the target material 10 is disk-shaped, the diameter of the main surface of the target material 10, preferably the diameter of the sputtering surface 10s, is not particularly limited, but is preferably 75 mm or more, more preferably 80 mm or more, still more preferably 90 mm or more, even more preferably 100 mm or more, and particularly preferably 200 mm or more. The area of the main surface of the target material 10, preferably the area of the sputtering surface 10s, is preferably 4500 mm 2 or more, more preferably 5000 mm 2 or more, still more preferably 6000 mm 2 or more, even more preferably 7500 mm 2 or more, and particularly preferably 15000 mm 2 or more.

[0016] The target material 10 may be in the form of a plate having a rectangular main surface. The length in the long side direction of the main surface of the target material 10, preferably the length in the long side direction of the sputtering surface 10s, is preferably 80 mm or more, more preferably 100 mm or more, still more preferably 120 mm or more, even more preferably 150 mm or more, and particularly preferably 200 mm or more. The length in the short side direction of the main surface of the target material 10, preferably the length in the short side direction of the sputtering surface 10s, is preferably 50 mm or more, more preferably 80 mm or more, and still more preferably 100 mm or more. The area of the main surface of the target material 10, preferably the area of the sputtering surface 10s, is preferably 4500 mm 2 or more, more preferably 5000 mm 2 or more, still more preferably 6000 mm 2 or more, even more preferably 7500 mm 2 or more, and particularly preferably 15000 mm 2 or more.

[0017] The thickness of the target material 10 is not particularly limited, but is preferably 3.0 mm or more, more preferably 5.0 mm or more, and still more preferably 7.5 mm or more, and is preferably 25 mm or less, more preferably 20 mm or less, and still more preferably 15 mm or less.

[0018] The backing plate (cooling plate) is made of a conductive material, which is a metal or an alloy thereof, such as Cu, Cu alloy, Al, Al alloy, Ti, stainless steel (SUS), etc. The size of the cooling plate is not particularly limited as long as it can join and support the target material 10 and can be attached to the sputtering apparatus, but it is preferably about the same size as the joining surface of the target material 10, and preferably larger.

[0019] As will be described in detail later, when manufacturing the target material 10, various raw material powders containing K, Na, and Nb are mixed, calcined, pulverized, etc., to prepare raw material powder (hereinafter referred to as KNN raw material powder). From the viewpoint of homogeneity of the powder, the KNN raw material powder is preferably an oxide containing K, Na, and Nb in a solid solution state. In this embodiment, a predetermined amount of KNN raw material powder is compacted by applying mechanical pressure, and at the same time, this compacted powder is heated by pulse current to sinter it, in a process known as spark plasma sintering (hereinafter simply referred to as SPS).

[0020] In this sintering process, in this embodiment, first, pulse current heating is performed on the compacted powder under relatively low mechanical pressure conditions to raise the heating temperature to 450°C or higher, thereby removing residual gases and other substances from the compacted powder (hereinafter, this process is also referred to as degassing or low-pressure SPS). Subsequently, pulse current heating is performed on the degassed compacted powder under relatively high mechanical pressure conditions greater than the size necessary to advance the sintering reaction, thereby sintering the compacted powder (hereinafter, this process is also referred to as high-pressure SPS).

[0021] In this embodiment, the target material 10 is sintered through a novel method that involves performing low-pressure SPS followed by high-pressure SPS. As a result, it not only has a high relative density but also possesses novel characteristics that are not present in target materials sintered by performing high-pressure SPS without low-pressure SPS, or in target materials sintered using the so-called hot press method. Specifically, the target material 10 in this embodiment possesses at least one of the characteristics 1 to 3 described later. As a result, the target material 10 in this embodiment further possesses at least one of the characteristics 4 to 7 related to mechanical strength, etc. The relative density of the target material 10 in this embodiment is 80% or more, preferably 85% or more, more preferably 90% or more, even more preferably 95% or more, and particularly preferably 98% or more across the entire sputtering surface. The relative density (%) referred to here is the value calculated by (measured density / theoretical density of KNN) × 100. The theoretical density of KNN is, for example, 4.52 g / cm³ for a KNN with (K / (Na+K)) = 0.35. 3 That is the case.

[0022] In this embodiment, the target material 10 is composed of crystal grains whose number-average particle diameter (hereinafter sometimes referred to as Nd) observed in a cross-section parallel to the sputtering surface 10s is, for example, 0.10 μm or more and 20 μm or less, preferably 0.15 μm or more and 10 μm or less, more preferably 0.20 μm or more and 5.0 μm or less, and particularly preferably 0.25 μm or more and 1.5 μm or less. Furthermore, the target material 10 is composed of crystal grains whose area-average particle diameter (hereinafter sometimes referred to as Nv) observed in a cross-section parallel to the sputtering surface 10s is, for example, 0.10 μm or more and 20 μm or less, preferably 0.20 μm or more and 10 μm or less, more preferably 0.30 μm or more and 5.0 μm or less, and particularly preferably 0.45 μm or more and 2.0 μm or less. When the number-average particle diameter and area-average particle diameter of the target material 10 are within the above ranges, it becomes easier to increase the mechanical strength of the target material 10. The number-average particle diameter and area-average particle diameter of the target material 10 in this embodiment are as described below. The number-average particle diameter and area-average particle diameter of the target material 10 in this embodiment are equivalent in both cases where the heat treatment in an oxygen-containing atmosphere or air (hereinafter sometimes referred to as oxidation treatment) is omitted in the manufacturing process described later, and when oxidation treatment is performed.

[0023] The following describes various novel features that the target material 10 of this embodiment may possess.

[0024] (Feature 1) One of the characteristics that the target material 10 may possess is, The number-average particle diameter Nd (μm) and area-average particle diameter Nv (μm) of multiple crystal grains of alkali niobium oxide observed on the sputtering surface at 10s satisfy the relationship (Nv-Nd) / Nd≦2.1. This is one example.

[0025] This characteristic can occur in the manufacturing process described later, both when the oxidation treatment is omitted and when the oxidation treatment is performed.

[0026] The number-average particle diameter Nd (μm) and the area-average particle diameter Nv (μm) can preferably be determined by analyzing the backscattered electron diffraction (EBSD) pattern of the sputtered surface 10s of the target material 10. The crystal grain diameter determined by EBSD analysis is shown by the diameter of a circle with the same area as the measured crystal grain, and the number-average particle diameter Nd (μm) can be the average particle diameter obtained by the number method in the EBSD measurement. In the number method, the value obtained by dividing the total area to be analyzed by the number of crystal grains becomes the average area of ​​the crystal grains, and [measurement area (μm)] 2 The average particle diameter is the diameter when the area calculated by [(measured area - area with CI value below the predetermined value) / number of crystals] is assumed to be a circle. When using OIM, a crystal orientation analysis software manufactured by TSL Solutions Co., Ltd., for analysis, if there are many voids, defects, etc. in the evaluation area of ​​the target material 10, the area in which the confidence index (CI value) defined in OIM is below a predetermined value can be excluded, and the crystal particle diameter can be calculated from the value of [(measured area - area with CI value below the predetermined value) / number of crystals], thereby calculating the average particle diameter with higher accuracy. On the other hand, the area-average particle diameter Nv (μm) can be the average particle diameter obtained by the Area Fraction method. In the Area Fraction method, the average area of ​​the crystal grains is the sum of the values ​​obtained by multiplying the area of ​​each crystal grain by the ratio that the area of ​​each crystal grain occupies to the total area, and the diameter when the calculated area is assumed to be a circle is the average particle diameter. In EBSD analysis, by considering boundaries where the crystal orientation difference is above a certain value, for example 15° or more, as grain boundaries, the number-average particle diameter Nd (μm) and the area-average particle diameter Nv (μm) can be determined.

[0027] Furthermore, the number-average particle diameter Nd (μm) and the area-average particle diameter Nv (μm) may be calculated using the following formulas. In the following formulas, d i The particle size (μm) of the observed crystal grains is n i The observed particle size d i The number of crystal grains with (μm) dimensions is shown for each. iThis is the diameter of a perfect circle having an area equal to the area of ​​the observed crystal grain, i.e., the equivalent diameter of the circle (μm).

[0028] Number average particle diameter Nd(μm)=Σ(d i ×n i ) / Σn i Area average particle diameter Nv(μm)=Σ(d i 3 ×n i ) / Σ(d i 2 ×n i )

[0029] The area-average particle diameter Nv (μm) is a weighted average value based on the size of the particle area. If some crystal grains grow larger than others, the area-average particle diameter Nv (μm) will be larger than the number-average particle diameter Nd (μm). In other words, the difference between the area-average particle diameter Nv (μm) and the number-average particle diameter Nd (μm) will increase, resulting in a larger value for (Nv-Nd) / Nd.

[0030] In this embodiment, the target material 10 employs a novel method in its manufacturing process that involves performing low-pressure SPS followed by high-pressure SPS. This method suppresses significant variations in grain size, meaning that some grains grow significantly larger than others, compared to cases where high-pressure SPS is performed without low-pressure SPS or when sintering is carried out using the hot-press method. As a result, the target material 10 in this embodiment achieves the aforementioned characteristics. Note that when high-pressure SPS is performed without low-pressure SPS or when sintering is carried out using the hot-press method, the variation in grain size becomes large, and the aforementioned characteristics are not achieved.

[0031] (Feature 2) One of the characteristics that the target material 10 may possess is, In multiple crystal grains observed on the sputtering surface at 10s, the area-average particle diameter Nv (μm) and the area-average standard deviation Ns (μm) satisfy the relationship Ns / Nv ≤ 0.76. This is one example.

[0032] This characteristic can occur in the manufacturing process described later, both when the oxidation treatment is omitted and when the oxidation treatment is performed.

[0033] The method for calculating the area-average particle diameter Nv (μm) is as described above. The area-average standard deviation Ns (μm) was calculated from the distribution of the crystal particle diameter (diameter when the crystal area is assumed to be a circle) of each crystal. The particle diameter of each crystal obtained in calculating the above area-average particle diameter is D i Therefore, it is calculated using the following formula. The area-averaged standard deviation Ns is preferably 1.30 μm or less.

[0034] Area average standard deviation Ns (μm) = [{Σ(D i -Nv) 2} / Σn i ] 1 / 2

[0035] (Feature 3) One of the characteristics that the target material 10 may possess is, The number-mean particle diameter Nd (μm) and the number-mean standard deviation Nn (μm) of multiple crystal grains observed on the sputtering surface at 10s satisfy the relationship Nn / Nd ≤ 0.80. This is one example.

[0036] This characteristic can occur in the manufacturing process described later, both when the oxidation treatment is omitted and when the oxidation treatment is performed.

[0037] The method for calculating the number-mean particle diameter Nd (μm) is as described above. The number-mean standard deviation Nn (μm) was calculated from the distribution of the crystal particle diameter (diameter when the crystal area is assumed to be a circle) of each crystal. The particle diameter of each crystal obtained in calculating the above number-mean particle diameter was D i Therefore, it is calculated using the following formula. The numerical mean standard deviation Nn is preferably 0.45 μm or less.

[0038] Number average standard deviation Nn (μm) = [{Σ(D i -Nd) 2} / Σn i ] 1 / 2

[0039] In this embodiment, the target material 10 employs a novel method in its manufacturing process that involves performing low-pressure SPS followed by high-pressure SPS. This method suppresses significant variations in grain size, meaning that some grains grow significantly larger than others, compared to cases where high-pressure SPS is performed without low-pressure SPS or when sintering is carried out using the hot-press method. As a result, the target material 10 in this embodiment achieves the aforementioned characteristics. Note that when high-pressure SPS is performed without low-pressure SPS or when sintering is carried out using the hot-press method, the variation in grain size becomes large, and the aforementioned characteristics are not achieved.

[0040] (Feature 4) One of the characteristics that the target material 10 may possess is, The volume resistivity at 25°C is 6.0 × 10⁻⁶ 11 It is less than Ω·cm, The Vickers hardness is 460 or higher, and the flexural strength is 90 MPa or higher. This is one example.

[0041] This characteristic may appear when the oxidation treatment is omitted in the manufacturing process described later. The Vickers hardness (Hv) of the target material 10 (or KNN sintered body) can be measured using a Vickers hardness tester in accordance with JIS R 1610:2003, for example, by the method described in the examples. The flexural strength of the target material 10 (or KNN sintered body) can be determined by a three-point bending test in accordance with JIS R 1601:2008, for example, by the method described in the examples.

[0042] In this embodiment, the target material 10 employs a novel method in which low-pressure SPS is performed before high-pressure SPS during its manufacturing process, thereby obtaining at least one of the above-described features 1 to 3. As a result, it becomes possible to increase both the Vickers hardness and flexural strength of the target material 10. However, if high-pressure SPS is performed without low-pressure SPS and sintering is carried out, or if sintering is carried out using the hot press method, the above-described features 1 to 3 will not be exhibited, and if oxidation treatment is omitted (volume resistivity at 25°C is 6.0 × 10⁻⁶). 11 When the density is less than Ω·cm, the above-mentioned characteristics regarding at least one of the Vickers hardness or flexural strength are not obtained.

[0043] (Feature 5) One of the characteristics that the target material 10 may possess is, The volume resistivity at 25°C is 6.0 × 10⁻⁶ 11 It is greater than Ω·cm, It has a Vickers hardness of 250 or higher and a flexural strength of 90 MPa or higher. This is one example.

[0044] This characteristic may appear when oxidation treatment is performed during the manufacturing process described later.

[0045] In this embodiment, the target material 10 employs a novel method in which low-pressure SPS is performed before high-pressure SPS during its manufacturing process, thereby obtaining at least one of the above-described features 1 to 3. As a result, it becomes possible to increase both the Vickers hardness and flexural strength of the target material 10. Note that if high-pressure SPS is performed without low-pressure SPS and sintering is carried out, or if sintering is carried out using the hot press method, the above-described features 1 to 3 will not be exhibited, and if oxidation treatment is performed (volume resistivity at 25°C is 6.0 × 10⁻⁶). 11 When the density is greater than or equal to Ω·cm, the above-mentioned characteristics regarding at least one of the Vickers hardness or flexural strength are not obtained.

[0046] (Feature 6) One of the characteristics that the target material 10 may possess is, The Vickers hardness after heat treatment under conditions of 900°C in air for 5 hours is maintained at more than 50% of the Vickers hardness before heat treatment. This is one example.

[0047] This characteristic can occur in the manufacturing process described later, both when the oxidation treatment is omitted and when the oxidation treatment is performed.

[0048] In this embodiment, the target material 10 employs a novel method in which low-pressure SPS is performed before high-pressure SPS during its manufacturing process, thereby obtaining at least one of the above-described features 1 to 3. As a result, the above-described features are obtained regarding the Vickers hardness before and after heat treatment. However, if high-pressure SPS is performed without low-pressure SPS and sintering is carried out, or if sintering is carried out using the hot press method, the above-described features 1 to 3 will not be exhibited, and the above-described features will not be obtained.

[0049] (Feature 7) One of the characteristics that the target material 10 may possess is, The relative density after heat treatment under the conditions of 900°C in air for 5 hours is maintained at more than 95% of the relative density before heat treatment. This is one example.

[0050] This characteristic can occur in the manufacturing process described later, both when the oxidation treatment is omitted and when the oxidation treatment is performed.

[0051] In this embodiment, the target material 10 employs a novel method in which low-pressure SPS is performed before high-pressure SPS during its manufacturing process, thereby obtaining at least one of the above-described features 1 to 3. As a result, the above-described features are obtained regarding the relative density before and after heat treatment. However, if high-pressure SPS is performed without low-pressure SPS and sintering is carried out, or if sintering is carried out using the hot press method, the above-described features 1 to 3 will not be exhibited, and the above-described features will not be obtained.

[0052] (2) Method for manufacturing the target material A preferred embodiment of the method for manufacturing the target material 10 in this embodiment will be described in detail with reference to Figures 2 and 3.

[0053] (Preparation of starting raw material powder) First, prepare starting material powders containing K, Na, and Nb, such as potassium carbonate (K2CO3) powder, sodium carbonate (Na2CO3) powder, and niobium pentoxide (Nb2O5) powder.

[0054] In this context, "powder consisting of K compounds" refers to powder whose main component is a K compound. This may include powders consisting solely of K compounds, or powders of other compounds in addition to the main component, the K compound. Similarly, "powder consisting of Na compounds" refers to powder whose main component is a Na compound. This may include powders consisting solely of Na compounds, or powders of other compounds in addition to the main component, the Na compound. "Powder consisting of Nb compounds" refers to powder whose main component is a Nb compound. This may include powders consisting solely of Nb compounds, or powders of other compounds in addition to the main component, the Nb compound. A K compound is at least one selected from the group consisting of K oxides, K complex oxides, and K compounds that become oxides upon heating. Examples include the carbonates mentioned above, as well as oxalates. A Na compound is at least one selected from the group consisting of Na oxides, Na complex oxides, and Na compounds that become oxides upon heating. Examples include the carbonates mentioned above, as well as oxalates. A Nb compound is at least one selected from the group consisting of Nb oxides, Nb complex oxides, or Nb compounds that become oxides upon heating, and examples include niobium pentoxide as shown above.

[0055] Furthermore, if necessary, a powder containing at least one dopant element selected from the group consisting of Li, Mg, Ca, Sr, Ba, Bi, Sb, V, In, Ta, Mo, W, Cr, Ti, Zr, Hf, Sc, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Cu, Zn, Ag, Mn, Fe, Co, Ni, Al, Si, Ge, Sn, and Ga may be prepared as a starting material powder. For example, a powder of the element itself, an oxide powder containing the element, a composite oxide powder containing the element, and a powder of a compound containing the element that becomes an oxide when heated (e.g., carbonate, oxalate).

[0056] The average particle size of these starting material powders is, for example, the median diameter D. 50It is preferable that the size is less than 1 mm, and if necessary, it is preferable to pre-grind the starting material powder before weighing.

[0057] (Weighing, mixing) Next, each of the starting material powders is weighed, and the mixing ratio of the starting material powders is adjusted so that the final composition of the target material 10 is the desired composition. Weighing may be done in the atmosphere, but it is preferable to do so in an atmosphere with low humidity, such as an inert gas atmosphere, a vacuum, or a dry air atmosphere, and it is also preferable to do so after each starting material powder has been thoroughly dried. Subsequently, the weighed starting material powders are mixed dry using a mixer such as a Henschel mixer, blender, ribbon mixer, super mixer, Nauter mixer, intensive mixer, or automatic mortar and pestle.

[0058] (Primary calcination, coarse grinding) The resulting mixed powder is subjected to primary calcination in an electric furnace or the like under an oxidizing atmosphere such as air or oxygen gas to obtain a calcined product containing K, Na, and Nb. Preferably, in the primary calcination, the mixed powder of the raw materials is subjected to a solid-phase reaction to obtain a calcined product in which K, Na, and Nb are in a solid-solution state. Subsequently, the obtained calcined product is coarsely ground using grinding means such as a ball mill, bead mill, vibratory mill, attritor, jet mill, atomizer, or cutter mill to obtain calcined powder (hereinafter referred to as KNN calcined powder). If K, Na, and Nb are in a solid-solution state during the primary calcination, KNN calcined powder in which K, Na, and Nb are in a solid-solution state (hereinafter referred to as KNN solid-solution powder) can be obtained.

[0059] The heating temperature during the primary firing is preferably 500°C or higher, more preferably 550°C or higher, even more preferably 600°C or higher, preferably 750°C or lower, and more preferably 700°C or lower. When the heating temperature is above the lower limit, it is easier to obtain KNN solid solution powder in which K, Na, and Nb are in a solid solution state, and it is easier to obtain a fired powder with high homogeneity. When the heating temperature is below the upper limit, it is easier to increase the BET specific surface area of ​​the KNN fired powder and KNN solid solution powder, and it is easier to obtain a fired powder with high sinterability.

[0060] The duration of the primary firing is not particularly limited, but is preferably 3 hours or more and 20 hours or less, more preferably 4 hours or more and 15 hours or less, and even more preferably 5 hours or more and 10 hours or less.

[0061] (Calibration, coarse grinding) The obtained KNN calcined powder (or KNN solid solution powder) is further calcined in an oxidizing atmosphere such as air or oxygen gas atmosphere, and then coarsely ground using a grinding method such as a ball mill, bead mill, vibratory mill, attritor, jet mill, or atomizer to obtain calcined KNN powder. By performing this calcination, impurities such as moisture, carbon components, and chlorine can be removed from the calcined KNN powder, and high-purity calcined KNN powder can be obtained.

[0062] The heating temperature during calcination is preferably 500°C or higher, more preferably 600°C or higher, even more preferably 650°C or higher, particularly preferably 700°C or higher, preferably 1150°C or lower, more preferably 1100°C or lower, and even more preferably 1000°C or lower. If the heating temperature is above the lower limit, it is easier to obtain calcined KNN powder of high purity, and if the heating temperature is below the upper limit, it is easier to obtain KNN raw material powder with a large BET specific surface area and high sinterability.

[0063] The heating time during pre-baking is not particularly limited, but is preferably 3 hours to 50 hours, more preferably 3.5 hours to 30 hours, even more preferably 4 hours to 20 hours, and most preferably 5 hours to 12 hours.

[0064] In the calcination process, from the viewpoint of easily removing impurities, multi-stage heat treatment may be performed at different heating temperatures.

[0065] (finely pulverized) The calcined KNN powder obtained by coarse grinding is further ground using grinding means such as a ball mill, bead mill, vibratory mill, attritor, atomizer, and jet mill, preferably a jet mill, and if necessary, is dried after grinding to obtain KNN raw material powder having predetermined specifications (specific surface area, impurity concentration, etc.).

[0066] For example, when grinding calcined powder with a jet mill, the processing speed is 1.0 kg / h or more and 8.0 kg / h or less, preferably 1.2 kg / h or more and 6.0 kg / h or less, and more preferably 1.5 kg / h or more and 3.0 kg / h or less. The introduction pressure is 0.1 MPa or more and 2.0 MPa or less, preferably 0.5 MPa or more and 1.8 MPa or less, and more preferably 1.0 MPa or more and 1.7 MPa or less, and the grinding pressure is 0.1 MPa or more and 2.0 MPa or less, preferably 0.5 MPa or more and 1.8 MPa or less, and more preferably 1.0 MPa or more and 1.7 MPa or less. Grinding calcined powder under the above conditions makes it easier to obtain raw material powder with a large BET specific surface area and high sinterability.

[0067] By following the above steps, KNN raw material powder for use in SPS sintering according to this embodiment is obtained. The BET specific surface area of ​​the KNN raw material powder is preferably 1.0 m². 2 / g or more, more preferably 2.0m 2 / g or more, more preferably 2.5m 2 / g or more, particularly preferably 3.0m 2 / g or more, preferably 10m 2 / g or less, more preferably 8.0m 2 Less than or equal to / g, more preferably 7.0m 2 / g or less, particularly preferably 6.0m 2 The BET specific surface area of ​​the KNN raw material powder is less than or equal to the above lower limit. If the BET specific surface area of ​​the KNN raw material powder is above the above lower limit, the sinterability is increased, and a high-density KNN sintered body is more easily obtained. Also, if the BET specific surface area of ​​the KNN raw material powder is below the above upper limit, the amount of gas components (e.g., gas components contained in the atmosphere, carbon dioxide, carbon monoxide, methane, etc.) and moisture adsorbed onto the raw material powder after manufacturing can be reduced, and a KNN sintered body with fewer impurities and voids is more easily obtained. The BET specific surface area of ​​the KNN raw material powder can be measured using a gas adsorption device and can be determined by the method described in the examples. The obtained KNN raw material powder can be used after being heated and dried under conditions such as 180-200°C, as needed.

[0068] Furthermore, the carbon concentration contained in the KNN raw material powder is preferably 250 ppm or less, and more preferably 200 ppm or less.

[0069] Furthermore, the processes described above—primary calcination, coarse grinding, calcination, coarse grinding, and jet mill grinding—can be partially or entirely repeated as needed, and any of these processes can be omitted. Additionally, sieving or other processes can be added after the completion of these processes or between them. The means of mixing and grinding are not limited to the examples given above, but can be broadly adopted from other grinding methods, and the conditions in such cases can also be broadly selected according to the purpose of obtaining the above specifications.

[0070] Next, a preferred embodiment of the low-pressure SPS and high-pressure SPS processes will be described with reference to Figure 3. Figure 3 is a schematic diagram of the sintering apparatus 100 used in these processes. The sintering apparatus 100 includes a chamber 101, a die 102, punches 103 and 104, pressurizing devices 105 and 106, a vacuum pump 110, a pressure gauge 111, a pulse current device 120, and the like.

[0071] (Low-pressure SPS) First, a predetermined amount of KNN raw material powder having the above specifications is filled into a cylindrical die (sintering mold) 102. Next, the die 102 filled with KNN raw material powder is placed inside a chamber 101 and positioned between a pair of upper and lower punches 103 and 104. Then, while evacuating the chamber 101 using a vacuum pump 110, the pressure inside the chamber 101 is monitored by a pressure gauge 111. The die 102 and punches 103 and 104 can be made of conductive material, but preferably they are made of carbon material such as graphite.

[0072] Once the desired pressure is reached in the chamber 101, the pressurizing devices 105 and 106 are activated to apply mechanical pressure to the KNN raw material powder filled in the die 102 via the punches 103 and 104, while the pulse energizing device 120 is used to start heating the KNN raw material powder by pulse energizing. Upon starting the pulse energizing, the temperature of the compacted powder, which is formed by pressurizing the KNN raw material powder, gradually rises from an initial temperature of approximately room temperature (25°C) to the predetermined degassing temperature shown below.

[0073] The degassing temperature is 450°C or higher, which is about the same as the sintering temperature in the pressurized SPS described below. However, the mechanical pressure applied at this time (degassing pressure) is much smaller than the mechanical pressure (sintering pressure) in the pressurized SPS. As a result, in low-pressure SPS, the sintering reaction of the KNN raw material powder in the compacted powder proceeds slowly, while degassing from the compacted powder due to simultaneous heating occurs more easily.

[0074] The mechanical pressure in the low-pressure SPS process should be such that stable current can be supplied to the SPS device, but from the viewpoint of easily discharging residual gas from the compacted powder, it is preferably 1 MPa or more, more preferably 5 MPa or more, even more preferably 7 MPa or more, and even more preferably 8 MPa or more. Preferably it is 15 MPa or less, more preferably 12 MPa or less, and even more preferably 10 MPa or less.

[0075] Furthermore, the degassing temperature in the low-pressure SPS process is preferably 500°C or higher, more preferably 600°C or higher, even more preferably 700°C or higher, even more preferably 800°C or higher, particularly preferably 900°C or higher, and also preferably 1200°C or lower, more preferably 1100°C or lower. When the degassing temperature in the low-pressure SPS process is within the above range, residual gas is easily discharged, and a sintered body with high mechanical strength is easily obtained.

[0076] The heating time at the degassing temperature is not particularly limited. The heating may be kept above the heating temperature for a certain period of time by providing a sufficient time for the temperature to rise, or the state at which the degassing temperature is reached may be maintained for a certain period of time. When the state at which the degassing temperature is reached is maintained, the maintenance time is preferably 5 minutes or more, more preferably 10 minutes or more, even more preferably 20 minutes or more, preferably 10 hours or less, more preferably 5 hours or less, even more preferably 3 hours or less, even more preferably 60 minutes or less, particularly preferably 50 minutes or less, and particularly more preferably 40 minutes or less.

[0077] Furthermore, in low-pressure SPS, heating is performed by pulsed current, and the effects of electromagnetic energy, Joule heating, and discharge plasma generated between particles allow residual gases (for example, gas molecules containing carbon monoxide, carbon dioxide, moisture, and chlorine-based impurities) adsorbed on the surface of the crystal grains to be efficiently degassed from the surface of the crystal grains and released from the compacted powder. In low-pressure SPS, while causing the sintering reaction of the KNN raw material powder, excessive growth of crystal grains can be suppressed, and degassing from the compacted powder can be efficiently performed, thereby reducing the voids in the compacted powder and making the compacted powder denser. In other words, it is possible to reduce the excess space around the crystal grains contained in the compacted powder and make the crystal grains more densely condensed.

[0078] When gas release from the compacted material begins, the pressure inside the chamber 101 increases, but once the gas release from the compacted material is complete, the pressure inside the chamber 101 decreases again. Therefore, by monitoring this pressure change with the pressure gauge 111, the timing of the completion of low-pressure SPS can be determined.

[0079] Other conditions for performing low-pressure SPS include the following: Green compact temperature (starting temperature): Room temperature (25℃) ~ 80℃ Ambient pressure (pressure inside the chamber): 10 Pa or less

[0080] (This pressurized SPS) Once the gas release from the compacted powder is complete, the mechanical pressure applied to the compacted powder is increased to a level greater than that in the low-pressure SPS while continuing to evacuate the chamber 101 and continuing to heat it by pulse current using the pulse current device 120. The mechanical pressure applied at this time (sintering pressure) is set to a level greater than or equal to the pressure necessary to sufficiently advance the sintering reaction of the compacted powder.

[0081] The mechanical pressure in this pressurized SPS process is preferably 25 MPa or higher, more preferably 30 MPa or higher, even more preferably 35 MPa or higher, preferably 70 MPa or lower, more preferably 60 MPa or lower, and even more preferably 50 MPa or lower, from the viewpoint of obtaining a high-density and crack-resistant sintered body.

[0082] Furthermore, the heating temperature in this pressurized SPS process is preferably 700°C or higher, more preferably 750°C or higher, even more preferably 800°C or higher, even more preferably 850°C or higher, particularly preferably 900°C or higher, and also preferably 1100°C or lower, more preferably 1000°C or lower, even more preferably 980°C or lower, particularly preferably 960°C or lower, from the viewpoint of obtaining a high-density and crack-resistant sintered body.

[0083] The heating time at the above heating temperature is not particularly limited. The heating may be maintained at or above the heating temperature for a certain period of time by providing sufficient time for the temperature to rise, or the state at a predetermined heating temperature may be maintained for a certain period of time. When the heating temperature is maintained for a certain period of time, the maintenance time is preferably 10 minutes or more, more preferably 15 minutes or more, even more preferably 20 minutes or more, preferably 240 minutes or less, more preferably 180 minutes or less, and even more preferably 120 minutes or less.

[0084] This process allows for the sintering of the compacted powder, resulting in a high-density sintered body. Compared to sintering using a hot press, sintering using SPS can proceed uniformly at a lower temperature and in a shorter time. This suppresses grain growth in the sintered body and makes the sintered body denser.

[0085] Other conditions for performing this pressurized SPS include the following: Ambient pressure (pressure inside the chamber): 10 Pa or less

[0086] Although one embodiment of low-pressure SPS and high-pressure SPS has been illustrated above, the SPS sintering may also be carried out in an inert atmosphere, for example, in an atmosphere consisting of an inert gas such as nitrogen, argon, helium, or hydrogen.

[0087] (Oxidation treatment) When low-pressure SPS or high-pressure SPS is performed, impurities such as carbon components are removed from the compacted powder, and some oxygen is removed from the oxide sintered body, which may slightly reduce the insulating properties of the final target material 10. Therefore, if necessary, after performing high-pressure SPS, the oxide sintered body may be heat-treated in an oxygen-containing atmosphere to increase its resistance and restore its insulating properties. Furthermore, this oxidation treatment can also further reduce impurities remaining after SPS sintering.

[0088] The oxidation treatment is carried out in an oxidizing atmosphere such as air and an oxygen-containing atmosphere at a heating temperature of 500°C to 1100°C, preferably 700°C to 1050°C, more preferably 800°C to 1020°C, and even more preferably 850°C to 1000°C. The heating time is 1 hour to 40 hours, preferably 2 hours to 20 hours, more preferably 3 hours to 10 hours, and even more preferably 4 hours to 7 hours.

[0089] The oxidation treatment can be omitted if necessary. If the oxidation treatment is omitted, the final target material 10 will be, for example, 6.0 × 10 at 25°C. 11 The volume resistivity will be less than Ω·cm. Furthermore, if oxidation treatment is performed, the final target material 10 will have a volume resistivity of, for example, 6.0 × 10 at 25°C. 11 This will result in a volume resistivity of Ω·cm or greater.

[0090] (Finishing process and joining to the backing plate) Subsequently, if necessary, the sintered body can be, for example, made with an area of ​​4500 mm². 2 As described above, the target material 10 in this embodiment can be obtained by grinding it into a disc shape with a thickness of 3 mm or more, or by polishing the surface to adjust the surface condition. The target material 10 is joined to a backing plate made of Cu or the like via a bonding material such as In, Sn, and alloys containing these metals, and is used as a sputtering target.

[0091] (3) Effects According to this embodiment, one or more of the following effects can be obtained.

[0092] (a) In this embodiment, the target material 10 is sintered by a novel method that involves performing low-pressure SPS followed by high-pressure SPS, and thus possesses at least one of the above-described features 1 to 3.

[0093] As a result, the target material 10 in this embodiment further possesses at least one of the above-described features 4 to 7 relating to mechanical strength, etc.

[0094] Furthermore, the target material 10 having the characteristics shown in features 4 and 5 is less prone to cracking, chipping, etc., both during machining such as grinding when manufacturing the target material 10 and during sputtering film formation using the target material 10. In addition, since abnormal discharges caused by cracking and chipping are less likely to occur during sputtering film formation, it becomes possible to suppress changes in composition and deterioration of properties of the resulting sputtered film (piezoelectric thin film).

[0095] Furthermore, since the target material 10 having the properties shown in features 6 and 7 exhibits little change in Vickers hardness and relative density before and after heat treatment, it can be used stably in sputtering film deposition processes and other processes where the target material 10 is subjected to high temperatures.

[0096] Furthermore, if sintering is performed using the high-pressure SPS method without performing low-pressure SPS, or if sintering is performed using the hot-press method, features 1 to 3 will not be exhibited, and as a result, none of the features shown in features 4 to 7 will be obtained.

[0097] (b) By appropriately selecting the manufacturing conditions of the target material 10 from the above-described range of conditions, it is possible to make (Nv-Nd) / Nd not only 2.1 or less, but preferably 1.5 or less, more preferably 1.0 or less, even more preferably 0.80 or less, even more preferably 0.70 or less, particularly preferably 0.60 or less, particularly more preferably 0.50 or less, and particularly still preferably 0.44 or less.

[0098] Furthermore, by appropriately selecting the manufacturing conditions for the target material 10 from within the above-mentioned condition range, it is possible to set Ns / Nv not only to 0.76 or less, but preferably to 0.70 or less, more preferably to 0.60 or less, even more preferably to 0.55 or less, even more preferably to 0.50 or less, and particularly preferably to 0.47 or less.

[0099] Furthermore, by appropriately selecting the manufacturing conditions for the target material 10 from within the above-mentioned condition range, it is possible to set the Nn / Nd ratio not only to 0.80 or less, but preferably to 0.70 or less, more preferably to 0.60 or less, even more preferably to 0.55 or less, even more preferably to 0.50 or less, and particularly preferably to 0.45 or less.

[0100] Furthermore, by appropriately selecting the manufacturing conditions for the target material 10 from within the above-mentioned condition range, it is possible to set Ns not only to 1.30 μm or less, but preferably to 1.20 μm or less, more preferably to 1.00 μm or less, even more preferably to 0.80 μm or less, and even more preferably to 0.70 μm or less.

[0101] Furthermore, by appropriately selecting the manufacturing conditions for the target material 10 from within the above-mentioned condition range, it is possible to set the Nn to not only 0.45 μm or less, but preferably 0.42 μm or less, more preferably 0.40 μm or less, and even more preferably 0.38 μm or less.

[0102] These results make it possible to further improve the mechanical strength properties of the target material 10.

[0103] Specifically, if oxidation treatment is omitted (volume resistivity at 25°C is 6.0 × 10⁻⁶ 11 In the case where the density is less than Ω·cm, the Vickers hardness can be set not only to 460 or higher, but preferably to 470 or higher, more preferably to 480 or higher, even more preferably to 490 or higher, even more preferably to 500 or higher, and especially preferably to 510 or higher. Furthermore, the flexural strength can be set not only to 90 MPa or higher, but preferably to 100 MPa or higher, more preferably to 110 MPa or higher, even more preferably to 120 MPa or higher, and even more preferably to 130 MPa or higher.

[0104] Furthermore, when oxidation treatment is performed (volume resistivity at 25°C is 6.0 × 10⁻⁶ 11 In the case where the density is Ω·cm or more, the Vickers hardness can be set not only to 210 or higher, but preferably to 250 or higher, more preferably to 300 or higher, even more preferably to 350 or higher, even more preferably to 400 or higher, particularly preferably to 450 or higher, and particularly more preferably to 500 or higher. Furthermore, the flexural strength can be set not only to 90 MPa or higher, but preferably to 100 MPa or higher, more preferably to 110 MPa or higher, even more preferably to 120 MPa or higher, and even more preferably to 130 MPa or higher.

[0105] Furthermore, these results make it possible to further improve the stability of the Vickers hardness and relative density of the target material 10 before and after heat treatment.

[0106] Specifically, it is possible to make the Vickers hardness after heat treatment under the conditions of air, 900°C, and 5 hours more than 50% greater than the Vickers hardness before heat treatment, and preferably more than 70%, more preferably more than 90%, more preferably more than 95%, and more preferably more than 100%.

[0107] Furthermore, it is possible to make the relative density after heat treatment under the conditions of 900°C in air for 5 hours more than 95% of the relative density before heat treatment, and preferably more than 97%, more preferably more than 99%, and more preferably more than 100%.

[0108] There are no particular restrictions on the lower limit of (Nv-Nd) / Nd. However, in cases where the relative density of the target material 10 exceeds 95%, it is preferable to set (Nv-Nd) / Nd to 0.10 or higher, preferably 0.20 or higher, more preferably 0.30 or higher, even more preferably 0.35 or higher, and particularly preferably 0.40 or higher, as this can more reliably suppress cracking and chipping of the target material 10.

[0109] Furthermore, there are no particular restrictions on the lower limit of Ns / Nv. However, in cases where the relative density of the target material 10 exceeds 95%, it is preferable to set Ns / Nv to 0.10 or higher, preferably 0.20 or higher, more preferably 0.30 or higher, even more preferably 0.35 or higher, and particularly preferably 0.40 or higher, as this can more reliably suppress cracking and chipping of the target material 10.

[0110] Furthermore, there are no particular restrictions on the lower limit of Nn / Nd. However, in cases where the relative density of the target material 10 exceeds 95%, it is preferable to set Nn / Nd to 0.10 or higher, preferably 0.20 or higher, more preferably 0.30 or higher, even more preferably 0.35 or higher, and particularly preferably 0.40 or higher, as this can more reliably suppress cracking and chipping of the target material 10.

[0111] Furthermore, there are no particular restrictions on the lower limit of Ns. However, in cases where the relative density of the target material 10 exceeds 95%, it is preferable to set Ns to 0.01 μm or more, preferably 0.05 μm or more, more preferably 0.10 μm or more, even more preferably 0.15 μm or more, and particularly preferably 0.20 μm or more, as this can more reliably suppress cracking and chipping of the target material 10.

[0112] Furthermore, there are no particular restrictions on the lower limit of Nn. However, in cases where the relative density of the target material 10 exceeds 95%, it is preferable to set Nn to 0.01 μm or more, preferably 0.05 μm or more, more preferably 0.08 μm or more, even more preferably 0.10 μm or more, and particularly preferably 0.12 μm or more, as this can more reliably suppress cracking and chipping of the target material 10.

[0113] <Other aspects of this disclosure> The various aspects of this disclosure have been described in detail above. However, this disclosure is not limited to the aspects described above and can be modified in various ways without departing from its essence. [Examples]

[0114] The present disclosure will be described in more detail below based on examples and comparative examples, but the present disclosure is not limited to the following examples. First, the apparatus, conditions, methods, etc., used when measuring the target materials prepared in the examples and comparative examples will be described.

[0115] <Crystal grain size of the target material> Sample preparation: Performed by polishing (after polishing with waterproof abrasive paper until any large scratches that would interfere with evaluation were removed, buff polishing was performed). Equipment: Hitachi High-Tech Corporation SU-70 Ultra-High Resolution Analytical Scanning Electron Microscope EBSD detector manufactured by TSL Solutions Co., Ltd. Analysis software: OIM Analysis Ver8, manufactured by TSL Solutions Co., Ltd. Measurement magnification: 3000x Measurement area: 30μm x 50μm Step size: 0.06 μm Grain boundary angle: 15° Crystallographic information of KNN: The space group and lattice constants were determined by X-ray diffraction, and the information shown in Table 1 below was used. Analysis Method: To remove noise, a cleanup process was performed, and a grain boundary map was created under the condition of a grain boundary angle of 15° (boundaries with a crystal orientation difference of 15° or more were considered crystal grain boundaries). The particle size was then analyzed. If voids or other defects were present, a threshold was set for the IQ (Image Quality) value. The area and particle size (equivalent circle diameter) of each particle were calculated using the EBSD Number method and Area Fraction method, and the number-average particle size, area-average particle size, and standard deviation were determined. Furthermore, when calculating the particle size, only particles larger than 0.20 μm were included in the calculation to remove parts with poor crystallinity that could not be analyzed and microcrystals as noise.

[0116] [Table 1]

[0117] <Vickers hardness> The Vickers hardness of the target materials in the examples and comparative examples was measured using the following apparatus, conditions, and methods. Equipment: Mitutoyo Corporation Micro Vickers Hardness Tester HM-114 Atmosphere: In the air Temperature: Room temperature (25℃) Test force: 1.0 kgf Load application acceleration: 10μm / s Holding time: 15sec Number of measurement points: 5 points Test Method: This test was conducted in accordance with JIS R 1610. A Vickers indenter (a square pyramidal indenter with a square base and an angle of 136 degrees between its two opposing faces) was used to create an indentation on the test surface. The Vickers hardness was determined from the test force applied and the indentation surface area calculated from the diagonal length of the indentation, and the average was calculated from the results of five measurements.

[0118] <Transverse bending strength> The flexural strength of the target materials in the examples and comparative examples was measured using the following apparatus, conditions, and methods. Equipment: Instron 5582 Universal Testing Machine (Load Cell 500N) Atmosphere: In the air Temperature: Room temperature (25℃) Test speed: 0.5 mm / min Distance between fulcrums: L=30mm Jig material: SiC Test Method: The test was evaluated using a three-point bending test in accordance with JIS R 1601. A test specimen (size: 3mm x 4mm x 40mm) was placed on two support points located at a fixed distance (30mm) apart. A load was applied to the central point between the support points, and the bending strength was determined from the maximum load at which the specimen broke.

[0119] <Relative Density> The relative densities of the target materials in the examples and comparative examples were measured using the following apparatus and method. Equipment: Alpha Mirage MDS300 Electronic Hydrometer Test method: The density of the target material, cut to a predetermined size, was measured using the Archimedes method with the above apparatus. The obtained density was compared to the theoretical density of KNN (4.52 g / cm³). 3 By dividing by ), the relative density (%) (= measured density / theoretical density × 100) was obtained.

[0120] <Insulation evaluation> The insulating properties of the target materials in the examples and comparative examples were evaluated by measuring the volume resistivity using the following apparatus, tests, and methods. Equipment: Screen printing machine, MODEL MEC=2400E, manufactured by Mitani Micronics Co., Ltd. Resistivity measuring device manufactured by Nishiyama Seisakusho Co., Ltd. ADC Corporation Digital Ultra-High Resistance / Micro-Current Meter, Model 5450 Test method: DC three terminal method Measurement temperature: room temperature (25℃) Measurement atmosphere: Argon atmosphere (using 99.9999% pure Ar, flow rate 300cc / min) Measurement method: Using a screen printing machine and a platinum paste manufactured by Tanaka Kikinzoku Kogyo K.K., main electrodes, guard electrodes were formed on the upper surface of a target material sample cut into a predetermined size, and a counter electrode was formed on the lower surface of the target material sample. Each electrode can be formed by drying the platinum paste printed on the sample at 150 °C for 12 hours and then performing a baking process (Ar atmosphere, 1000 °C) using an atmospheric tube furnace. After holding the sample with electrodes for 15 minutes in an environment at room temperature (25 °C), a DC voltage of 100 V was applied, the current after charging for 1 minute was measured, the volume resistance of the sample was determined, and the volume resistivity was calculated from the thickness and electrode area of the sample.

[0121] <BET specific surface area of KNN raw material powder> The BET specific surface area of the KNN raw material powder obtained in the production example was measured by the BET single-point method using nitrogen adsorption with a specific surface area measuring device (Monosorb, manufactured by Quantachrome Instruments).

[0122] [Production of KNN raw material powder 1] <Production Example 1> As starting raw material powders, K2CO3 powder, Na2CO3 powder, and Nb2O5 powder were prepared. By mixing the raw material powders, firing at 650 °C for 7 hours, and pulverizing according to the method described in JP-A-2018-197181 so that, in terms of atoms, sodium is 32.5 mol%, potassium is 17.5 mol%, niobium is 50.0 mol%, the ratio of alkali metals to niobium ((Na + K) / Nb) is 1.00, and the ratio of potassium to sodium and potassium (K / (Na + K)) is 0.35, KNN raw material powder 1 in which K, Na, and Nb are solid-dissolved was obtained. The composition of the obtained KNN raw material powder 1 was measured by a high-frequency inductively coupled plasma optical emission spectrometer after acid dissolution, and it was confirmed that it was almost the same as the charged ratio. By X-ray diffraction analysis, it was confirmed that it is a solid solution of K, Na, and Nb. Also, the BET specific surface area of KNN raw material powder 1 was 6.9 m 2 / g.

[0123] [Production of KNN raw material powder 2] <Production Example 2> The KNN raw material powder 1 obtained in Production Example 1 was calcined in an electric furnace at 750°C for 5 hours, followed by 1000°C for 5 hours. The calcined KNN raw material powder 1 was then pulverized in a jet mill (NanoJetmizer NJ100, manufactured by Aisin Nano Technologies Co., Ltd.) under the conditions of a processing speed of 2 kg / h, an introduction pressure of 1.4 MPa, and a grinding pressure of 1.4 MPa to obtain KNN raw material powder 2. The BET specific surface area of ​​the obtained KNN raw material powder 2 was 4.0 m². 2 It was / g.

[0124] [Manufacturing of KNN raw material powder 3] <Manufacturing Example 3> The KNN raw material powder 1 obtained in Production Example 1 was fired in an electric furnace at 750°C for 5 hours, followed by 1000°C for 5 hours, to obtain KNN raw material powder 3. The BET specific surface area of ​​the obtained KNN raw material powder 3 was 3.3 m². 2 It was / g.

[0125] [Manufacturing of KNN raw material powder 4] <Manufacturing Example 4> The KNN raw material powder 1 obtained in Production Example 1 was fired in an electric furnace at 750°C for 5 hours, followed by 900°C for 5 hours, to obtain KNN raw material powder 4. The BET specific surface area of ​​the obtained KNN raw material powder 4 was 3.6 m². 2 It was / g.

[0126] [Manufacturing of KNN raw material powder 5] <Manufacturing Example 5> K2CO3 powder, Na2CO3 powder, and Nb2O5 powder were prepared as starting material powders. They were mixed so that the [K / (K+Na)] value was 0.35 and the [(Na+K) / Nb] value was 1.00. MnO powder and CuO powder were also mixed in to contain Mn and Cu at predetermined concentrations. The mixture was calcined at 650°C for 7 hours, and then pulverized to obtain KNN raw material powder 5, in which K, Na, and Nb were dissolved in solid solution. The composition of the obtained KNN raw material powder 5 was measured after acid dissolution using a high-frequency inductively coupled plasma atomic emission spectrometer, and it was confirmed to be approximately as per the initial charge ratio. X-ray diffraction analysis confirmed that it was a solid solution of K, Na, and Nb. The BET specific surface area of ​​KNN raw material powder 5 was 6.9 m². 2 It was / g.

[0127] [Manufacturing of KNN raw material powder 6] <Manufacturing Example 6> The KNN raw material powder 5 obtained in Production Example 5 was calcined in an electric furnace at 1000°C for 5 hours. The calcined KNN raw material powder 1 was pulverized in a jet mill (NanoJetmizer NJ100 model, manufactured by Aisin Nanotechnologies Corporation) at a processing speed of 2 kg / h, an introduction pressure of 1.4 MPa, and a grinding pressure of 1.4 MPa to obtain KNN raw material powder 6. The BET specific surface area of ​​the obtained KNN raw material powder 6 was 4.4 m². 2 It was / g.

[0128] [Example 1] The KNN raw material powder 2 obtained in Manufacturing Example 2 was heated to 200°C and dried, then set in a pulse current pressurized sintering apparatus SPS9.40MK-VII (manufactured by SPS Syntex Co., Ltd.) equipped with a graphite die measuring φ170mm × φ101.6mm × t100mm and a graphite punch measuring φ101.6mm × t65mm. Under a vacuum atmosphere (atmospheric pressure less than 10 Pa), heating by discharge plasma was started under a pressurized pressure of 10 MPa, and the temperature was increased from 25°C to 900°C at a rate of 50°C / min. During this time, desorption of gas components and an increase in atmospheric pressure were observed. After gradually increasing the pressure to 35 MPa, the temperature was increased to 950°C at a rate of 2.5°C / min and held at 950°C for 30 minutes. After that, the current and pressurization were stopped and the material was cooled to obtain a disc-shaped target material (KNN sintered body, low insulating target material) with a diameter of approximately 101 mm and a thickness of 5 mm.

[0129] Furthermore, the obtained target material was subjected to oxidation treatment at 900°C for 5 hours under atmospheric pressure, and then the surface was ground to finish it, resulting in a KNN target material (a highly insulating target material) with a diameter of 100 mm and a thickness of 5 mm.

[0130] The composition of the obtained target material was measured using a high-frequency inductively coupled plasma atomic emission spectrometer after microwave decomposition, and it was confirmed that the [K / (K+Na)] value was 0.35 and the [(Na+K) / Nb] value was 1.0.

[0131] <Conditions for low-pressure SPS> Mechanical pressure: 10 MPa Heating temperature: ~900℃ Ambient pressure (pressure inside the chamber): Less than 10 Pa (30 Pa when rising)

[0132] <Conditions for this pressurized SPS> Mechanical pressure: 35 MPa (pressurization starts at 900°C) Heating temperature: 950℃ Ambient pressure (pressure inside the chamber): Less than 10 Pa

[0133] [Example 2] A KNN target material with a diameter of 100 mm and a thickness of 5 mm was obtained in the same manner as in Example 1, except that the KNN raw material powder 3 obtained in Production Example 3 was used and the pressurized SPS was carried out under the conditions shown below.

[0134] <Conditions for this pressurized SPS> Mechanical pressure: 30 MPa (pressurization starts at 900°C) Heating temperature: 1020°C (Increase temperature from 900°C at a rate of 10°C / minute, hold at 1020°C for 75 minutes after reaching 1020°C) Ambient pressure (pressure inside the chamber): Less than 10 Pa

[0135] [Example 3] A KNN target material with a diameter of 100 mm and a thickness of 5 mm was obtained in the same manner as in Example 1, except that the KNN raw material powder 4 obtained in Production Example 4 was used and the pressurized SPS was carried out under the conditions shown below.

[0136] <Conditions for this pressurized SPS> Mechanical pressure: 40 MPa (pressurization starts at 900°C) Heating temperature: 900~1010℃ (Increase temperature from 900℃ to 1010℃ at a rate of 2.5℃ / minute, no holding time) Ambient pressure (pressure inside the chamber): Less than 10 Pa

[0137] [Example 4] A KNN target material with a diameter of 100 mm and a thickness of 5 mm was obtained in the same manner as in Example 1, except that the KNN raw material powder 6 obtained in Production Example 6 was used, and low-pressure SPS and high-pressure SPS were carried out under the conditions shown below.

[0138] <Conditions for low-pressure SPS> Mechanical pressure: 5 MPa Heating temperature (temperature during degassing): ~800°C (heating from 25°C to 800°C at a rate of 3°C / min) Ambient pressure (pressure inside the chamber): Less than 10 Pa (30 Pa when rising)

[0139] <Conditions for this pressurized SPS> Mechanical pressure: 40 MPa (pressurization starts at 800°C) Heating temperature: 900°C (Increase temperature from 800°C to 900°C at a rate of 3°C / minute, then maintain temperature for 3 hours) Ambient pressure (pressure inside the chamber): Less than 10 Pa

[0140] [Comparative Example 1] A KNN target material with a diameter of 100 mm and a thickness of 5 mm was obtained in the same manner as in Example 1, except that the KNN raw material powder 1 obtained in Production Example 1 was used, and low-pressure SPS and high-pressure SPS were carried out under the conditions shown below.

[0141] <Conditions for low-pressure SPS> Mechanical pressure: 10 MPa Heating temperature: 400°C (heat from 25°C to 400°C at a rate of 40°C / minute, then maintain temperature for 50 minutes) Ambient pressure (pressure inside the chamber): Less than 10 Pa (20 Pa when rising)

[0142] <Conditions for this pressurized SPS> Mechanical pressure: 40 MPa (pressurization starts at 400°C) Heating temperature: ~915°C (Increase temperature from 400°C to 600°C at a rate of 10°C / min, hold for 20 minutes, increase temperature to 700°C at a rate of 5°C / min, hold for 30 minutes, then increase temperature to 915°C at a rate of 1.3°C / min, hold for 45 minutes) Ambient pressure (pressure inside the chamber): Less than 10 Pa

[0143] <Evaluation regarding crystal grain size> The sputtered surfaces of the target materials prepared in Examples 1-4 and Comparative Example 1 were observed using EBSD, and the number-average particle diameter Nd (μm), area-average particle diameter Nv (μm), number-average standard deviation Nn (μm), area-average standard deviation Ns (μm), (Nv-Nd) / Nd, Ns / Nv, and Nn / Nd were calculated for multiple crystal grains observed on the sputtered surface.

[0144] Furthermore, the Vickers hardness, relative density, and flexural strength of the target materials for Examples 1-4 and Comparative Example 1 were measured, respectively.

[0145] The Vickers hardness and relative density of the target material were determined based on the state before oxidation treatment (volume resistivity at 25°C was 6.0 × 10⁻⁶). 11 (State where the volume resistivity is less than Ω·cm), and the state after oxidation treatment (volume resistivity at 25°C is 6.0 × 10⁻⁶). 11 Measurements were taken at two timings (when the value was Ω·cm or greater). Note that the target materials obtained in both the examples and comparative examples all had a volume resistivity of 6.0 × 10⁻⁶ at 25°C before oxidation treatment. 11 The resistivity is less than Ω·cm, and the volume resistivity at 25°C after oxidation treatment is 6.0 × 10⁻⁶. 11 The flexural strength was greater than Ω·cm. The flexural strength was measured after the oxidation treatment. Note that the flexural strength does not change as a result of the oxidation treatment, or it decreases slightly due to the removal of carbon as an impurity from the sintered body; therefore, the flexural strength before oxidation treatment is greater than or equal to the flexural strength after oxidation treatment.

[0146] These measurement results are shown in Table 2.

[0147] [Table 2]

[0148] In all of the target materials in Examples 1 to 4, the area-average particle diameter Nv (μm) and area-average standard deviation Ns (μm) were relatively small, and it was confirmed that (Nv-Nd) / Nd was 2.1 or less, and Ns / Nv was 0.76 or less.

[0149] Furthermore, it was confirmed that the Vickers hardness of the target materials in Examples 1 to 4 was 460 or higher before oxidation treatment and 250 or higher after oxidation treatment. In addition, it was confirmed that the flexural strength of the target materials in Examples 1 to 4 was 90 MPa or higher after oxidation treatment. From this, it could be inferred that the flexural strength of the target materials in Examples 1 to 4 was 90 MPa or higher even before oxidation treatment. Because the target materials in Examples 1 to 4 possessed these mechanical strength characteristics, it was confirmed that no cracks or chips occurred during grinding or during the subsequent sputtering film formation process.

[0150] Furthermore, when comparing the Vickers hardness of the target materials in Examples 1 to 4 before and after oxidation treatment, it was found that there was no significant change in these values. This confirmed that the Vickers hardness after heat treatment (oxidation treatment) was maintained at more than 50% of the Vickers hardness before heat treatment.

[0151] Furthermore, when comparing the relative densities of the target materials in Examples 1 to 4 before and after oxidation treatment, these values ​​did not change significantly, and it was confirmed that the relative density after heat treatment (oxidation treatment) was maintained at more than 95% of the relative density before heat treatment.

[0152] In contrast, in the target material of Comparative Example 1, the area-average particle diameter Nv (μm) and area-average standard deviation Ns (μm) were relatively large, and it was confirmed that (Nv-Nd) / Nd exceeded 2.1 and Ns / Nv exceeded 0.76.

[0153] Furthermore, it was confirmed that the Vickers hardness of the target material in Comparative Example 1 was less than 460 before oxidation treatment and less than 250 after oxidation treatment. In addition, it was confirmed that the flexural strength of the target material in Comparative Example 1 was less than 90 MPa after oxidation treatment. From this, it could be inferred that the flexural strength of Comparative Example 1 was less than 90 MPa even before oxidation treatment. It was confirmed that cracks and chips occurred in the target material of Comparative Example 1 both during grinding and during the subsequent sputtering film deposition process. In the sputtering film deposition process, a sputtering target was used in which the target material was joined to an oxygen-free copper backing plate with in-solder.

[0154] Furthermore, when comparing the Vickers hardness of the target material in Comparative Example 1 before and after oxidation treatment, these values ​​changed significantly. It was confirmed that the Vickers hardness after heat treatment (oxidation treatment) decreased to less than 50% of the Vickers hardness before heat treatment.

[0155] Furthermore, when comparing the relative density of the target material in Comparative Example 1 before and after oxidation treatment, these values ​​also changed relatively significantly, confirming that the relative density after heat treatment (oxidation treatment) decreased to less than 95% of the relative density before heat treatment.

[0156] Furthermore, in Examples 1 to 4, the number mean standard deviation Nn was 0.45 μm or less, the area mean standard deviation Ns was 1.30 μm or less, and Nn / Nd was 0.80 or less. These values ​​were smaller and the variability was smaller compared to Comparative Example 1.

[0157] <Preferred aspects of this disclosure> The following are preferred embodiments of this disclosure.

[0158] (Note 1) According to one aspect of this disclosure, A sputtering target material comprising a sintered body of an oxide containing potassium, sodium, niobium, and oxygen, The number-average particle diameter Nd and area-average particle diameter Nv of multiple crystal grains observed on the sputtered surface satisfy the relationship (Nv-Nd) / Nd≦2.1. A sputtering target material is provided.

[0159] (Note 2) According to other aspects of this disclosure, A sputtering target material comprising a sintered body of an oxide containing potassium, sodium, niobium, and oxygen, The area-average particle diameter Nv and area-average standard deviation Ns of multiple crystal grains observed on the sputtered surface satisfy the relationship Ns / Nv ≤ 0.76. A sputtering target material is provided.

[0160] (Note 3) According to yet another aspect of this disclosure, A sputtering target material comprising a sintered body of an oxide containing potassium, sodium, niobium, and oxygen, The number-mean particle diameter Nd and the number-mean standard deviation Nn of multiple crystal grains observed on the sputtered surface satisfy the relationship Nn / Nd ≤ 0.80. A sputtering target material is provided.

[0161] (Note 4) According to yet another aspect of this disclosure, A sputtering target material comprising a sintered body of an oxide containing potassium, sodium, niobium, and oxygen, The volume resistivity at 25°C is 6.0 × 10⁻⁶ 11 It is less than Ω·cm, It has a Vickers hardness of 460 or higher and a flexural strength of 90 MPa or higher. A sputtering target material is provided.

[0162] (Note 5) According to yet another aspect of this disclosure, A sputtering target material comprising a sintered body of an oxide containing potassium, sodium, niobium, and oxygen, The volume resistivity at 25°C is 6.0 × 10⁻⁶ 11 It is greater than Ω·cm, It has a Vickers hardness of 250 or higher and a flexural strength of 90 MPa or higher. A sputtering target material is provided.

[0163] (Note 6) Preferably, The Vickers hardness after heat treatment under conditions of 900°C in air for 5 hours is maintained at more than 50% of the Vickers hardness before the heat treatment.

[0164] (Note 7) Preferably, The relative density after heat treatment under the conditions of 900°C in air for 5 hours is maintained at more than 95% of the relative density before the heat treatment.

[0165] (Note 8) Preferably, The dopant contains at least one element selected from the group consisting of Li, Mg, Ca, Sr, Ba, Bi, Sb, V, In, Ta, Mo, W, Cr, Ti, Zr, Hf, Sc, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Cu, Zn, Ag, Mn, Fe, Co, Ni, Al, Si, Ge, Sn, and Ga.

[0166] (Note 9) Preferably, Main surface is 4500mm 2 It has the above area.

[0167] (Note 10) According to yet another aspect of this disclosure, A sputtering target material described in any one of the appendices 1 to 9, A backing plate bonded to the sputtering target material, A sputtering target is provided that includes the following features. [Explanation of Symbols]

[0168] 10 Target material 10s sputtered surface

Claims

1. A sputtering target material comprising a sintered body of an oxide represented by the compositional formula (K 1-x Na x)NbO 3 (0 < x < 1), In multiple crystal grains observed on the sputtered surface, Number-average particle size Nd is 0.1 μm or more and 20 μm or less. Area-average particle diameter Nv is 0.1 μm or more and 20 μm or less. The mean standard deviation Nn is 0.45 μm or less. The area-average standard deviation Ns is 1.30 μm or less. The relationship (Nv - Nd) / Nd ≤ 2.1 is satisfied. Sputtering target material.

2. A sputtering target material comprising a sintered body of an oxide represented by the compositional formula (K 1-x Na x)NbO 3 (0 < x < 1), In multiple crystal grains observed on the sputtered surface, Number-average particle size Nd is 0.1 μm or more and 20 μm or less. Area-average particle diameter Nv is 0.1 μm or more and 20 μm or less. Area-average standard deviation Ns is 1.30 μm or less. The number mean standard deviation Nn is 0.45 μm or less. The relationship Ns / Nv ≤ 0.76 is satisfied. Sputtering target material.

3. The dopant contains at least one element selected from the group consisting of Li, Mg, Ca, Sr, Ba, Bi, Sb, V, In, Ta, Mo, W, Cr, Ti, Zr, Hf, Sc, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Cu, Zn, Ag, Mn, Fe, Co, Ni, Al, Si, Ge, Sn, and Ga. The sputtering target material according to claim 1 or 2.

4. Main surface: 4500 mm ２ Having the above area A sputtering target material according to any one of claims 1 to 3.

5. A sputtering target material according to any one of claims 1 to 4, A backing plate bonded to the sputtering target material, A sputtering target equipped with the following features.

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