JP2023075689A - Sputtering target material and sputtering target - Google Patents

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 ratio of a total area of cavities in a unit area of a sputter surface is equal to or less than 12.0%, and a mean diameter of cavities existing in the sputter surface is equal to or less than 0.60 μm.SELECTED DRAWING: Figure 1

Description

The present disclosure relates to sputtering target materials and sputtering targets.

As a material for forming a piezoelectric thin film, a sputtering target material (hereinafter also 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 is used. There is a case (for example, see Patent Document 1).

JP 2011-146623 A

An object of the present disclosure is to improve the properties of KNN target materials.

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,
The ratio of the total area of voids per unit area of the sputtering surface is 12.0% or less,
A sputtering target material is provided in which the average diameter of voids present on the sputtering surface is 0.60 μm or less.

According to another aspect of the present disclosure,
a sputtering target material according to any of the above aspects;
a backing plate bonded to the sputtering target material;
A sputtering target is provided comprising:

According to the present disclosure, it is possible to improve the properties of the KNN target material.

FIG. 1 is a diagram illustrating one aspect of a target material 10 of the present disclosure. FIG. 2 is a diagram illustrating the manufacturing flow of the target material 10 of the present disclosure. FIG. 3 is a schematic configuration diagram of a sintering apparatus 100 used in the present disclosure.

<One aspect of the present disclosure>
One aspect of the present disclosure will be described below mainly with reference to FIGS. 1 to 3. FIG.

(1) Structure of target material The target material 10 in this embodiment mainly contains potassium (K), sodium (Na), niobium (Nb), and an oxide (alkali niobium oxide) containing oxygen (O). It is composed of a sintered body, that is, a KNN sintered body. Crystal grains that mainly constitute the KNN sintered body have a perovskite structure. The KNN sintered body is specifically represented by the composition formula (K _1−x Na _x )NbO ₃ (0<x<1), and the coefficient x [=Na/(K+Na)] in the composition formula is , 0<x<1, preferably 0.4≦x≦0.8. The KNN sintered body constituting the target material 10 of this embodiment is an oxide sintered body substantially composed of potassium, sodium, niobium and oxygen, or an oxide sintered body further containing dopant elements shown below. Here, "substantially" means that 99% or more of all atoms constituting the KNN sintered body are composed of potassium, sodium, niobium, and oxygen, or when the KNN sintered body contains a dopant element , potassium, sodium, niobium, oxygen and dopant elements.

The composition of K, Na, and Nb ((K+Na)/Nb) in the target material 10 is 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. It satisfies the relationship of 1.10 or less. K, Na, and Nb in the formula (K+Na)/Nb are the numbers of K atoms, Na atoms, and Nb atoms, respectively, contained in the KNN sintered body. The composition ratio of the target material 10 can also be estimated from the charged amount of raw materials, but can also be measured by a known method. It can be obtained by SPS5000 manufactured by Co., Ltd., etc.).

At least one element (dopant) selected from the group shown below may be added to the target material 10 at a concentration of, for example, 5 at % or less. 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 (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 at least one element selected from the group consisting of gallium (Ga). When a plurality of the above elements are contained, the total concentration is 5 at % or less, and the dopant addition amount is usually 0.1 at % or more.

The target material 10 is formed, for example, in a disc shape, and is bonded onto a backing plate (cooling plate) (not shown) made of Cu or the like via a bonding material such as In, Sn, or an alloy containing these metals ( attached) and used as a sputtering target. Of the two main surfaces of the target material 10, the surface different from the bonding surface with the cooling plate is the surface exposed to plasma such as argon (Ar) during the film forming process, that is, the atoms constituting the film. It is used as the emitting sputter surface 10s.

When the target material 10 is disc-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, and further preferably 90 mm or more. More preferably 100 mm or more, 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 4,500 mm ² or more, more preferably 5,000 mm ² or more, still more preferably 6,000 mm ² or more, still more preferably 7,500 mm ² or more, and particularly preferably 15000 mm ² or more.

The target material 10 may have a plate shape with a rectangular main surface, and the length of the main surface of the target material 10 in the long side direction, preferably the length of the sputtering surface 10s in the long side direction, is It is preferably 80 mm or more, more preferably 100 mm or more, even more preferably 120 mm or more, even more preferably 150 mm or more, and particularly preferably 200 mm or more. The length of the main surface of the target material 10 in the short side direction, preferably the length of the sputtering surface 10s in the short side direction 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 4,500 mm ² or more, more preferably 5,000 mm ² or more, still more preferably 6,000 mm ² or more, still more preferably 7,500 mm ² or more, and particularly preferably 15000 mm ² or more.

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, still more preferably 7.5 mm or more, preferably 25 mm or less, more preferably 20 mm or less, and even more preferably. is 15 mm or less.

The backing plate (cooling plate) is made of a conductive material, and is made of metal or its alloy, such as Cu, Cu alloy, Al, Al alloy, Ti, stainless steel (SUS), and the like. The size of the cooling plate is not particularly limited as long as it can bond and support the target material 10 and can be attached to the sputtering apparatus. .

Although details will be described 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). do. The KNN raw material powder is preferably an oxide containing K, Na, and Nb in a solid solution from the viewpoint of powder homogeneity. In this embodiment, a predetermined amount of the KNN raw material powder is subjected to mechanical pressure to form a green compact, and at the same time, the green compact is sintered by heating by pulse energization. So-called spark plasma sintering (Spark Plasma Sintering, hereinafter also simply referred to as SPS) is performed.

During this sintering treatment, in this aspect, first, the green compact is subjected to pulse electric heating under relatively low mechanical pressure conditions so that the heating temperature is 450 ° C. or higher, and the green compact is Residual gases and the like are discharged from the body (hereinafter, this treatment is also referred to as degassing or low-pressure SPS). After that, the green compact after degassing is subjected to pulse electric heating under relatively high mechanical pressure conditions that are greater than or equal to the magnitude necessary for the sintering reaction to proceed, thereby sintering the green compact. (hereinafter, this process is also referred to as main pressurization SPS).

Since the target material 10 in this embodiment is sintered through a new method of performing low-pressure SPS and then performing main-pressure SPS, it not only has a high relative density, but also low-pressure SPS. A target material that is sintered by performing this pressurized SPS without performing it or a target material that is sintered using a so-called hot press method will have new features that do not appear. Specifically, the target material 10 in this aspect has at least one of features 1 and 2 to be described later. As a result, the target material 10 in this aspect further has at least one of features 3 to 6 relating to mechanical strength and the like. The relative density of the target material 10 in this embodiment is 80% or higher, preferably 85% or higher, more preferably 90% or higher, still more preferably 95% or higher, and particularly preferably 98% or higher over the entire sputtering surface. The relative density (%) referred to here is a value calculated by (actual density/theoretical density of KNN)×100. The theoretical density of KNN is, for example, 4.52 g/cm ³ in KNN with (K/(Na+K)) of 0.35.

The target material 10 in this embodiment has a number average particle diameter observed in a cross section parallel to the sputtering surface 10s of, 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. It is composed of crystal grains of 5.0 μm or less, particularly preferably 0.25 μm or more and 1.5 μm or less. Further, the area-average particle diameter 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, especially Preferably, it is composed of crystal grains of 0.45 μm or more and 2.0 μm or less. When the number average particle size and area average particle size of the target material 10 are within the above ranges, the mechanical strength of the target material 10 can be easily increased. The number-average particle size and area-average particle size of the target material 10 in this embodiment are preferably obtained by analyzing an Electron Back Scattered Diffraction Pattern (EBSD) image of the sputtering surface 10s of the target material 10, respectively. can be obtained by The crystal grain size determined by EBSD analysis is indicated by the diameter of a circle having the same area as the measured crystal grains, and the number average particle size Nd (μm) is the average particle size determined by the Number method in EBSD measurement. can be adopted. In the Number method, the value obtained by dividing the total area to be analyzed by the ^number of crystal grains is the average area of the crystal grains. is the average particle size. When using crystal orientation analysis software OIM manufactured by TSL Solutions Co., Ltd. for analysis, when many voids, defects, etc. are seen in the area to be evaluated of the target material 10, the reliability index (Confidence Index: CI value) is less than a predetermined value, and the crystal grain size is calculated from the value of [(measurement area-area where the CI value is less than a predetermined value) / number of crystals], so that the average particle size can be calculated with higher accuracy. can be calculated. On the other hand, as the area average particle diameter Nv (μm), the average particle diameter obtained by the Area Fraction method can be adopted. The total value of the calculated values is the average area of the crystal grains, and the diameter when the calculated area is assumed to be a circle is the average particle diameter. In the EBSD analysis, the number-average grain size Nd (μm) and the area-average grain size Nv (μm) are obtained by regarding the boundary where the crystal orientation difference is a certain value or more, for example, 15° or more, as the grain boundary. can be done.

Also, the number average particle size Nd (μm) and the area average particle size Nv (μm) may each adopt values calculated using the following formulas. In the following equations, d _i indicates the observed grain size (μm), and _ni indicates the number of grains having the observed grain size d _i (μm). d _i is the diameter of a perfect circle having an area equal to the area of the observed crystal grain, that is, the equivalent circle diameter (μm).

Number average particle size 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 )

The area-average particle diameter Nv (μm) is an average value weighted according to the size of the particle area. When some crystal grains grow larger than other crystal grains, the area average particle size Nv (μm) becomes larger than the number average particle size Nd (μm), but the target material 10 in this aspect The difference between the area average particle size Nv (μm) and the number average particle size Nd (μm) is small, and the difference (Nv−Nd) is preferably 1.1 μm or less, more preferably 1.0 μm or less, and even more preferably It is 0.75 μm or less, particularly preferably 0.50 μm or less, and the value of (Nv−Nd)/Nd is small, and the value is preferably 2.1 or less, preferably 1.5 or less, more preferably 1 0.0 or less, more preferably 0.80 or less, still more preferably 0.70 or less, particularly preferably 0.60 or less, and even more preferably 0.50 or less, and the uniformity of the particle size is excellent. Regarding the number average particle size and area average particle size of the target material 10 in this embodiment, heat treatment in an oxygen-containing atmosphere or air (hereinafter sometimes referred to as oxidation treatment) is omitted in the manufacturing process described later. Equivalent values are obtained both in the case where oxidation treatment is performed and in the case where oxidation treatment is performed.

Various new features that the target material 10 of this embodiment can have will be described below.

(Feature 1)
As one of the features that the target material 10 can have,
Sv / S × 100 [%], which is the ratio of the total area Sv of the voids present in the observation field to the observation area S on the sputtering surface 10 s, that is, the ratio of Sv per unit area of the sputtering surface 10 s (hereinafter referred to as (also referred to as porosity) is 12.0% or less,
and the average diameter of the voids present on the sputtering surface 10s is 0.60 μm or less,
Things are mentioned.

This feature can appear when an oxidation treatment is performed in the manufacturing process described below.

The voids appear in the sputtering surface 10s due to voids or the like generated inside the target material 10, and are observed as openings of recessed spaces in the sputtering surface 10s. The total area of the voids present in the sputtering surface 10s and the average diameter of the voids can be determined by analyzing an optical microscope image or a scanning electron microscope (hereinafter sometimes referred to as SEM) image of the sputtering surface 10s using image analysis software. It can be calculated by The total area of the voids means the total value of the flat areas (cross-sectional areas) of the openings, and is obtained by calculating the total area of the voids by the image analysis. By calculating the ratio of the total area, the ratio of the total area of the voids can be obtained. The average diameter of voids is the average value of circle-equivalent diameters (μm) of a plurality of voids observed in an arbitrary observation field within the sputtering surface 10s, and this value exists on the sputtering surface 10s. It becomes substantially the same as the average diameter of the voids. The average diameter of the voids is, for example, the area of each void calculated by image analysis, and the equivalent circle diameter (50% area average diameter).

In the target material 10 in this aspect, in the manufacturing process, by adopting a new method of performing the main pressure SPS after performing the low pressure SPS, the main pressure is not performed without performing the low pressure SPS. Compared to sintering by performing SPS or sintering by hot pressing, it is possible to suppress the appearance of voids in the sputtering surface 10 s and to make the voids minute, as described above. characteristics can be obtained. In addition, when sintering is performed by performing main pressure SPS without performing low pressure SPS, or when sintering by using a hot press method, at least one of the porosity and the average diameter of the pores The above-mentioned features for are not obtained.

(Feature 2)
As one of the features that the target material 10 can have,
The maximum diameter of the voids present on the sputtering surface 10s is 1.0 μm or less,
Things are mentioned.

This feature can appear when an oxidation treatment is performed in the manufacturing process described below.

The maximum diameter of the void is the equivalent circle diameter (μm) of the void having the largest size among the plurality of voids observed in an arbitrary observation field within the sputtering surface 10s, and this value is It is substantially the same as the maximum diameter of the voids present on the sputtering surface 10s. In the target material 10 in this aspect, in the manufacturing process, by adopting a new method of performing the main pressure SPS after performing the low pressure SPS, the main pressure is not performed without performing the low pressure SPS. Compared to sintering by SPS or sintering by hot pressing, the voids can be made smaller, and the above characteristics can be obtained. In addition, when sintering is performed by performing main pressure SPS without performing low pressure SPS, or when sintering is performed using a hot press method, the above characteristics cannot be obtained.

(Feature 3)
As one of the features that the target material 10 can have,
A volume resistivity at 25° C. of less than 6.0×10 ¹¹ Ω·cm,
Vickers hardness is 460 or more, bending strength is 90 MPa or more,
Things are mentioned.

This characteristic can be expressed 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 according to JIS R 1610:2003, for example, by the method described in Examples. In addition, the bending strength of the target material 10 (or KNN sintered body) can be obtained by a three-point bending test in accordance with JIS R 1601: 2008, and can be measured, for example, by the method described in Examples. .

In the target material 10 in this aspect, in the manufacturing process, by adopting a novel method of performing the low pressure SPS and then performing the main pressure SPS, at least one of the above features 1 and 2 characteristics can be obtained. As a result, while increasing the Vickers hardness of the target material 10, it is also possible to increase the transverse strength. In addition, when sintering is performed by performing main pressure SPS without performing low pressure SPS, or when sintering is performed using a hot press method, the above-mentioned features 1 and 2 are not expressed, and oxidation When the treatment is omitted (when the volume resistivity at 25° C. is less than 6.0×10 ¹¹ Ω·cm), the above characteristics of at least one of Vickers hardness and bending strength cannot be obtained.

(Feature 4)
As one of the features that the target material 10 can have,
A volume resistivity at 25° C. of 6.0×10 ¹¹ Ω·cm or more,
Vickers hardness is 250 or more, bending strength is 90 MPa or more,
Things are mentioned.

This feature can appear when an oxidation treatment is performed in the manufacturing process described below.

In the target material 10 in this aspect, in the manufacturing process, by adopting a novel method of performing the low pressure SPS and then performing the main pressure SPS, at least one of the above features 1 and 2 characteristics can be obtained. As a result, while increasing the Vickers hardness of the target material 10, it is also possible to increase the transverse strength. In addition, when sintering is performed by performing main pressure SPS without performing low pressure SPS, or when sintering is performed using a hot press method, the above-mentioned features 1 and 2 are not expressed, and oxidation When the treatment is performed (when the volume resistivity at 25° C. is 6.0×10 ¹¹ Ω·cm or more), the above-described characteristics of at least one of Vickers hardness and bending strength cannot be obtained.

(Feature 5)
As one of the features that the target material 10 can have,
The Vickers hardness after heat treatment at 900 ° C. for 5 hours in the air is maintained at a value exceeding 50% of the Vickers hardness before heat treatment.
Things are mentioned.

This feature can be expressed both when the oxidation treatment is omitted and when the oxidation treatment is performed in the manufacturing process described later.

In the target material 10 in this aspect, in the manufacturing process, by adopting a novel method of performing the low pressure SPS and then performing the main pressure SPS, at least one of the above features 1 and 2 As a result, the above-mentioned characteristics can be obtained with respect to the Vickers hardness before and after the heat treatment. In addition, when sintering is performed by performing main pressure SPS without performing low pressure SPS, or when sintering by using a hot press method, the above-mentioned features 1 and 2 are not expressed, and the above-mentioned characteristics are not obtained.

(Feature 6)
As one of the features that the target material 10 can have,
The relative density after heat treatment under the conditions of 900 ° C. for 5 hours in the air is maintained at a magnitude exceeding 95% with respect to the relative density before heat treatment.
Things are mentioned.

This feature can be expressed both when the oxidation treatment is omitted and when the oxidation treatment is performed in the manufacturing process described later.

In the target material 10 in this aspect, in the manufacturing process, by adopting a novel method of performing the low pressure SPS and then performing the main pressure SPS, at least one of the above features 1 and 2 As a result, the above-described characteristics can be obtained with respect to the relative density before and after the heat treatment. In addition, when sintering is performed by performing main pressure SPS without performing low pressure SPS, or when sintering by using a hot press method, the above-mentioned features 1 and 2 are not expressed, and the above-mentioned characteristics are not obtained.

(2) Method for Manufacturing Target Material A preferred embodiment of the method for manufacturing the target material 10 in this aspect will be described in detail with reference to FIGS. 2 and 3. FIG.

(Preparation of starting raw material powder)
First, starting raw material powders include K-containing powder, Na-containing powder, and Nb-containing powder, such as potassium carbonate (K ₂ CO ₃ ) powder, sodium carbonate (Na ₂ CO ₃ ) powder, and niobium pentoxide (Nb _{2 )} . O ₅ ) Prepare flour.

In addition, the "powder composed of the compound of K" here means a powder composed mainly of the compound of K, and in addition to the case where it is composed only of the powder of the compound of K, the powder composed of K as the main component In addition to the powder of the compound, powders of other compounds may also be included. Similarly, "powder composed of a Na compound" means a powder composed mainly of a Na compound, and in addition to the case where it is composed only of a Na compound powder, the Na compound as a main component powder of other compounds may be included in addition to the powder of "Powder composed of Nb compound" means powder composed mainly of Nb compound, and in addition to the case where it is composed only of Nb compound powder, powder of Nb compound as the main component In addition to the powders of other compounds may also be included. The compound of K is at least one selected from the group consisting of an oxide of K, a composite oxide of K, and a compound of K that becomes an oxide by heating. , oxalates, and the like. The compound of Na is at least one selected from the group consisting of an oxide of Na, a composite oxide of Na, and a compound of Na that becomes an oxide by heating. oxalate and the like. The compound of Nb is at least one selected from the group consisting of oxides of Nb, composite oxides of Nb, and compounds of Nb that become oxides upon heating. mentioned.

In addition, if necessary, as starting raw material powders, Li, Mg, Ca, Sr, Ba, Bi, Sb, V, In, Ta, Mo, W, Cr, Ti, Zr, Hf, Sc, Y, La, Ce, the group consisting of Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Cu, Zn, Ag, Mn, Fe, Co, Ni, Al, Si, Ge, Sn, Ga A powder containing at least one dopant element selected from the above, for example, a powder of the element alone, an oxide powder containing the element, a composite oxide powder containing the element, and the element that becomes an oxide by heating. A powder of a compound (eg, carbonate, oxalate) is prepared.

As for the average particle size of these starting raw material powders, for example, the median diameter _D50 is preferably less than 1 mm, and if necessary, the starting raw material powders are preferably coarsely pulverized in advance before weighing.

(weighing, mixing)
Subsequently, each of the starting raw material powders is weighed, and the mixing ratio of the starting raw material powders is adjusted so that the finally obtained target material 10 has a desired composition. Weighing may be carried out in the air, but it is preferable to carry out the weighing in an atmosphere with low humidity such as in an inert gas atmosphere, in a vacuum or in a dry air atmosphere. preferably. Subsequently, the weighed starting material powders are dry-mixed using a mixer such as a Henschel mixer, a blender, a ribbon mixer, a super mixer, a Nauta mixer, an intensive mixer and an automatic mortar.

(primary firing, coarse pulverization)
The obtained mixed powder is primarily fired using an electric furnace or the like in an oxidizing atmosphere such as air or an oxygen gas atmosphere to obtain a fired product containing K, Na, and Nb. Preferably, in the primary sintering, a sintered product in which K, Na, and Nb are in a solid solution state is obtained by causing a solid phase reaction of the mixed powder of raw materials. After that, the fired product obtained is coarsely ground using a grinding means such as a ball mill, a bead mill, a vibration mill, an attritor, a jet mill, an atomizer, or a cutter mill to obtain a fired powder (hereinafter referred to as KNN fired powder). When K, Na, and Nb are in a solid solution state in the primary firing, a KNN fired powder in which K, Na, and Nb are in a solid solution state (hereinafter referred to as KNN solid solution powder) can be obtained.

The heating temperature for primary firing is preferably 500° C. or higher, more preferably 550° C. or higher, still more preferably 600° C. or higher, and preferably 750° C. or lower, more preferably 700° C. or lower. When the heating temperature is at least the above lower limit, it is easy to obtain a KNN solid-solution powder in which K, Na, and Nb are in a solid solution state, and it is easy to obtain a highly homogeneous fired powder. When the heating temperature is equal to or lower than the above upper limit, the BET specific surface area of the KNN sintered powder and the KNN solid-solution powder can be easily increased, and a highly sinterable sintered powder can be easily obtained.

The primary firing time 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 still more preferably 5 hours or more and 10 hours or less.

(calcination, coarse grinding)
The obtained KNN sintered powder (or KNN solid solution powder) is further calcined in an oxidizing atmosphere such as an atmosphere or an oxygen gas atmosphere, and then subjected to a ball mill, bead mill, vibration mill, attritor, jet mill, or atomizer. KNN calcined powder is obtained by coarsely pulverizing by a pulverizing means such as. By performing the calcination, impurities such as moisture, carbon components, and chlorine can be removed from the KNN calcined powder, and a KNN calcined powder with high purity can be obtained.

The heating temperature for calcination is preferably 500°C or higher, more preferably 600°C or higher, still more preferably 650°C or higher, particularly preferably 700°C or higher, and preferably 1150°C or lower, more preferably 1100°C. 1000° C. or less, more preferably 1000° C. or less. When the heating temperature is at least the above lower limit, it is easy to obtain a KNN calcined powder with high purity.

The heating time during calcination is not particularly limited, but is preferably 3 hours or more and 50 hours or less, more preferably 3.5 hours or more and 30 hours or less, still more preferably 4 hours or more and 20 hours or less, and particularly preferably 5 hours or more. 12 hours or less.

In the calcining step, multistage heat treatment may be performed at different heating temperatures from the viewpoint of facilitating removal of impurities.

(fine pulverization)
The KNN calcined powder obtained by coarse pulverization is further pulverized using a pulverizing means such as a ball mill, bead mill, vibration mill, attritor, atomizer, and jet mill, preferably a jet mill, and dried after pulverization as necessary. Thus, a KNN raw material powder having predetermined specifications (specific surface area, impurity concentration, etc.) is obtained.

For example, when pulverizing the 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, 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, more preferably 1.0 MPa or more and 1.7 MPa or less, and the pulverization pressure is 0.1 MPa or more and 2.0 MPa or more. 0 MPa or less, preferably 0.5 MPa or more and 1.8 MPa or less, more preferably 1.0 MPa or more and 1.7 MPa or less. When the calcined powder is pulverized under the above conditions, it becomes easier to obtain a raw material powder having a large BET specific surface area and high sinterability.

Through the above steps, the KNN raw material powder used for the SPS sintering of this embodiment is obtained. The BET specific surface area of the KNN raw material powder is preferably 1.0 m ² /g or more, more preferably 2.0 m ² /g or more, still more preferably 2.5 m ² /g or more, and particularly preferably 3.0 m ² /g. It is preferably 10 m ² /g or less, more preferably 8.0 m ² /g or less, even more preferably 7.0 m ² /g or less, and particularly preferably 6.0 m ² /g or less. When the BET specific surface area of the KNN raw material powder is at least the above lower limit, the sinterability is enhanced, and a high-density KNN sintered body can be easily obtained. In addition, when the BET specific surface area of the KNN raw material powder is equal to or less than the above upper limit, gas components adsorbed to the raw material powder after production (for example, gas components contained in the atmosphere, carbon dioxide, carbon monoxide, methane, etc.) The water content can be reduced, and a KNN sintered body with few impurities and voids can be easily obtained. The BET specific surface area of the KNN raw material powder can be measured with a gas adsorption apparatus and obtained by the method described in the Examples. The obtained KNN raw material powder is dried by heating at, for example, 180 to 200° C., if necessary.

Also, the concentration of carbon contained in the KNN raw material powder is preferably 250 ppm or less, preferably 200 ppm or less.

It should be noted that some or all of the above-described treatments such as primary firing, coarse pulverization, calcining, coarse pulverization, and jet mill pulverization can be repeated as necessary, and any of the treatments can be omitted. be able to. In addition, a sieving process or the like can be added after these processes are completed or between each process. Mixing and pulverization means are not limited to the above examples, and can be widely adopted from other pulverization means, and the conditions at that time can also be widely selected according to the purpose of obtaining the above specifications. can be done.

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

(low pressure SPS)
First, a predetermined amount of KNN raw material powder having the above specifications is filled in a cylindrical die (sintering mold) 102 . Next, the die 102 filled with the KNN raw material powder is accommodated in the chamber 101 and arranged between the pair of upper and lower punches 103 and 104 . Then, the pressure inside the chamber 101 is monitored by the pressure gauge 111 while the inside of the chamber 101 is being evacuated using the vacuum pump 110 . The die 102 and the punches 103 and 104 may be made of a conductive material, preferably a carbon material such as graphite.

When the chamber 101 reaches a desired pressure, the pressurizing devices 105 and 106 are operated to apply mechanical pressure to the KNN raw material powder filled in the die 102 via the punches 103 and 104 while applying a pulse. Using the energizing device 120, heating of the KNN raw material powder by pulse energization is started. With the start of the pulse energization, the temperature of the green compact formed by pressurizing the KNN raw material powder gradually rises from the starting temperature of about room temperature (25° C.) to the predetermined degassing temperature shown below. becomes.

The degassing temperature is 450° C. or higher, and can be set to a temperature similar to the sintering temperature in the main pressurized SPS described below, but the mechanical pressure applied at this time (degassing pressure) is much smaller than the mechanical pressure (sintering pressure) in this pressurized SPS. As a result, in the low-pressure SPS, the sintering reaction of the KNN raw material powder in the green compact progresses slowly, and at the same time, the green compact is easily degassed by heating.

The mechanical pressure in the low-pressure SPS step may be 1 MPa or more, more preferably 1 MPa or more, more preferably, from the viewpoint of easy discharge of residual gas from the green compact, although it is sufficient that the SPS apparatus allows stable energization. It is 5 MPa or higher, more preferably 7 MPa or higher, and even more preferably 8 MPa or higher. It is preferably 15 MPa or less, more preferably 12 MPa or less, still more preferably 10 MPa or less.

The degassing temperature in the low pressure SPS step is preferably 500° C. or higher, more preferably 600° C. or higher, still more preferably 700° C. or higher, still more preferably 800° C. or higher, and particularly preferably 900° C. or higher. It is preferably 1200° C. or lower, more preferably 1100° C. or lower. When the degassing temperature in the low-pressure SPS step is within the above range, residual gas is easily discharged, and a sintered body with high mechanical strength is easily obtained.

The heating time at the above degassing temperature is not particularly limited, and by providing a sufficient heating time, heating may be performed at the above heating temperature or higher for a certain period of time, or the state when the degassing temperature is reached. It may be held for a certain period of time. When the state of reaching the degassing temperature is maintained, the holding time is preferably 5 minutes or longer, more preferably 10 minutes or longer, still more preferably 20 minutes or longer, and preferably 10 hours or shorter, more preferably 5 minutes. hours or less, more preferably 3 hours or less, even more preferably 60 minutes or less, particularly preferably 50 minutes or less, and even more preferably 40 minutes or less.

In addition, in the low pressure SPS, since heating is performed by pulse energization, the residual gas (for example, gas molecules (including carbon monoxide, carbon dioxide, moisture, and chlorine-based impurities) can be efficiently desorbed from the surface of the crystal grains and released from the green compact. In the low-pressure SPS, the sintering reaction of the KNN raw material powder can be induced, and excessive growth of crystal grains can be suppressed while efficiently degassing the green compact. It is possible to reduce the voids and densify the green compact. That is, it is possible to reduce the excess space around the crystal grains contained in the powder compact, and to make the crystal grains more densely condensed.

When the gas release from the green compact starts, the pressure in the chamber 101 increases, but when the gas release from the green compact is completed, the pressure in the chamber 101 decreases again. Therefore, by monitoring this pressure change with the pressure gauge 111, it is possible to determine the completion timing of the low pressurization SPS.

Other conditions for performing low pressure SPS are as follows.
Green compact temperature (starting temperature): room temperature (25°C) to 80°C
Atmospheric pressure (pressure in chamber): 10 Pa or less

(Main pressure SPS)
When the release of gas from the green compact is completed, the mechanical pressure applied to the green compact is reduced while continuing to evacuate the chamber 101 and continue heating by pulse energization using the pulse energizing device 120. Greater than the mechanical pressure in pressurized SPS. The mechanical pressure applied at this time (pressure during sintering) is set to a pressure that is greater than or equal to the magnitude required for sufficiently advancing the sintering reaction of the green compact.

The mechanical pressure in the main pressure SPS step is preferably 25 MPa or more, more preferably 30 MPa or more, still more preferably 35 MPa or more, and preferably 70 MPa or less, from the viewpoint of obtaining a sintered body with high density and resistance to cracking. , more preferably 60 MPa or less, still more preferably 50 MPa or less.

In addition, the heating temperature in the main pressurized SPS step is preferably 700° C. or higher, more preferably 750° C. or higher, still more preferably 800° C. or higher, from the viewpoint of obtaining a sintered body with high density and resistance to cracking. It is preferably 850° C. or higher, particularly preferably 900° C. or higher, more preferably 1100° C. or lower, more preferably 1000° C. or lower, still more preferably 980° C. or lower, and particularly preferably 960° C. or lower.

The heating time at the above heating temperature is not particularly limited, and it may be heated at the heating temperature or higher for a certain period of time by providing a sufficient heating time, or the state of reaching the predetermined heating temperature is maintained for a certain period of time. may be retained. When the heating temperature is held for a certain period of time, the holding time is preferably 10 minutes or more, more preferably 15 minutes or more, still more preferably 20 minutes or more, preferably 240 minutes or less, more preferably 180 minutes or less, and further It is preferably 120 minutes or less.

By performing this treatment, it becomes possible to sinter the powder compact and obtain a high-density sintered compact. In the sintering treatment using SPS, compared to the sintering treatment using hot press, sintering can be uniformly progressed at a lower sintering temperature in a short time. Grain growth of grains can be suppressed, and the sintered body can be densified.

Other conditions for performing the pressurization SPS are exemplified below.
Atmospheric pressure (pressure in chamber): 10 Pa or less

An embodiment of the low-pressure SPS and the main-pressure SPS was exemplified above. You can go with

(Oxidation treatment)
When low-pressure SPS or high-pressure SPS is performed, impurities such as carbon components are desorbed from the green compact, while oxygen is partially desorbed from the oxide sintered body. In some cases, the insulation properties of the target material 10 that is typically obtained are slightly deteriorated. Therefore, if necessary, after performing the main pressure SPS, the oxide sintered body may be heat-treated in an oxygen-containing atmosphere to increase the resistance and restore the insulation. In addition, the oxidation treatment can further reduce impurities remaining during SPS sintering.

The oxidation treatment is carried out in an oxidizing atmosphere such as the air and an oxygen-containing atmosphere at 500° C. or higher and 1100° C. or lower, preferably 700° C. or higher and 1050° C. or lower, more preferably 800° C. or higher and 1020° C. or lower, further preferably 850° C. or higher. It is carried out at a heating temperature of 1000° C. or less. The heating time is 1 hour or more and 40 hours or less, preferably 2 hours or more and 20 hours or less, more preferably 3 hours or more and 10 hours or less, and still more preferably 4 hours or more and 7 hours or less.

Note that the oxidation treatment can be omitted if necessary. If the oxidation treatment is omitted, the finally obtained target material 10 will have a volume resistivity of less than 6.0×10 ¹¹ Ω·cm at 25° C., for example. Moreover, when the oxidation treatment is performed, the finally obtained target material 10 has a volume resistivity of 6.0×10 ¹¹ Ω·cm or more at 25° C., for example.

(Finish processing, bonding to backing plate)
After that, if necessary, the sintered body is ground into a disk shape having dimensions of, for example, an area of 4500 mm ² or more and a thickness of 3 mm or more, or the surface is polished to adjust the surface condition, thereby A target material 10 in the aspect is obtained. The target material 10 is bonded to a backing plate made of Cu or the like via a bonding material such as In, Sn, or an alloy containing these metals, and used as a sputtering target.

(3) Effect According to this aspect, one or more of the following effects can be obtained.

(a) Since the target material 10 in this embodiment is sintered by a new method of performing low-pressure SPS and then performing full-pressure SPS, the above-mentioned characteristics 1 and 2 It will have at least one of the features.

As a result, the target material 10 in this aspect further has at least one of the features 3 to 6 described above regarding mechanical strength and the like.

In addition, the target material 10 having the characteristics shown in features 3 and 4 is not cracked, Chipping or the like is less likely to occur. In addition, since abnormal discharge due to cracking and chipping is less likely to occur during sputtering film formation, it is possible to suppress changes in the composition and deterioration of the properties of the obtained sputtering film (piezoelectric thin film).

In addition, since the target material 10 having the characteristics shown in features 5 and 6 does not easily change in Vickers hardness and relative density before and after the heat treatment, the target material 10 can be stably used in a sputtering film forming process where the temperature of the target material 10 is high. can be used.

In addition, when sintering is performed by performing main pressure SPS without performing low pressure SPS, or when sintering is performed using a hot press method, neither features 1 and 2 are expressed, resulting in , none of the features shown in features 3 to 6 are obtained.

(b) When the oxidation treatment is performed by appropriately selecting the manufacturing conditions of the target material 10 from the above condition range (when the volume resistivity at 25° C. is 6.0×10 ¹¹ Ω·cm or more) , the porosity is not only 12.0% or less, but preferably 10.0% or less, more preferably 8.00% or less, even more preferably 6.00% or less, and even more preferably 4.00% %, particularly preferably 2.00% or less, particularly more preferably 1.00% or less, and even more preferably 0.75% or less. Instead, it is preferably 0.50 μm or less, more preferably 0.40 μm or less, still more preferably 0.30 μm or less, and even more preferably 0.25 μm or less.

In addition, by appropriately selecting the manufacturing conditions of the target material 10 from the above-described condition range, when the oxidation treatment is performed (when the volume resistivity at 25 ° C. is 6.0 × 10 ¹¹ Ω cm or more) , the maximum diameter of the voids is not only 1.0 μm or less, but also preferably 0.80 μm or less, more preferably 0.62 μm or less, still more preferably 0.60 μm or less, even more preferably 0.50 μm or less, especially Preferably, it becomes possible to make it 0.40 μm or less.

In these cases, the mechanical strength of the target material 10 can be further improved.

Specifically, when the oxidation treatment is performed (when the volume resistivity at 25° C. is 6.0×10 ¹¹ Ω·cm or more), the Vickers hardness is not only 210 or more, but preferably 250. 300 or more, more preferably 350 or more, still more preferably 400 or more, particularly preferably 450 or more, and particularly preferably 500 or more. In addition, the bending strength can be not only 90 MPa or more, but also preferably 100 MPa or more, more preferably 110 MPa or more, still more preferably 120 MPa or more, and even more preferably 130 MPa or more.

As a result, it is possible to further improve the stability of the Vickers hardness and relative density of the target material 10 before and after the heat treatment.

Specifically, when the oxidation treatment is performed, the Vickers hardness after heat treatment at 900 ° C. for 5 hours in the atmosphere is more than 50% of the Vickers hardness before heat treatment. It is possible not only to scale, but also to scale preferably above 70%, more preferably above 90%, more preferably above 95%, more preferably above 100%.

In addition, the relative density after heat treatment under the conditions of 900 ° C. for 5 hours in the air is not only greater than 95%, but preferably 97%, relative to the relative density before heat treatment. Greater than 99%, more preferably greater than 100%, can be achieved.

There is no particular limitation on the lower limit of the porosity. However, when the relative density of the target material 10 exceeds 95%, the porosity is 0.05% or more, preferably 0.10% or more, more preferably 0.15% or more, and further preferably 0. When the content is 0.20% or more, and more preferably 0.25% or more, the stress generated by the heat load during sputtering can be relaxed, and cracking and chipping of the target material 10 during sputtering can be suppressed more reliably. Like and preferred.

Also, there is no particular limitation on the lower limit of the average diameter of the voids. However, when the relative density of the target material 10 exceeds 95%, the average diameter of the voids should be 0.05 μm or more, preferably 0.10 μm or more, more preferably 0.15 μm or more, further preferably 0.15 μm or more. When the thickness is 20 μm or more, and more preferably 0.22 μm or more, the stress generated by the heat load during sputtering can be relaxed, and cracking and chipping of the target material 10 during sputtering can be suppressed more reliably. ,preferable.

Also, there is no particular limitation on the lower limit of the maximum diameter of the voids. However, when the relative density of the target material 10 exceeds 95%, the maximum diameter of the voids should be 0.08 μm or more, preferably 0.12 μm or more, more preferably 0.18 μm or more, further preferably 0.18 μm or more. By setting the thickness to 20 μm or more, more preferably 0.25 μm or more, particularly preferably 0.30 μm or more, and even more preferably 0.35 μm or more, the stress generated by the heat load during sputtering can be relaxed, particularly during sputtering. Cracking and chipping of the target material 10 can be suppressed more reliably, which is preferable.

<Other aspects of the present disclosure>
Various aspects of the present disclosure have been specifically described above. However, the present disclosure is not limited to the embodiments described above, and various modifications can be made without departing from the scope of the present disclosure.

EXAMPLES 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 produced in Examples and Comparative Examples will be described.

<Crystal grain size of target material>
Sample preparation: Conducted by the polishing method (After polishing with water-resistant abrasive paper, buffing was performed until there were no large scratches that interfered with the evaluation.)
Apparatus: Ultra-high resolution analytical scanning electron microscope SU-70 manufactured by Hitachi High-Tech Co., Ltd.
EBSD detector manufactured by TSL Solutions Co., Ltd. Analysis software: OIM Analysis Ver8 manufactured by TSL Solutions Co., Ltd.
Measurement magnification: 3000 times Measurement area: 30 μm × 50 μm
Step size: 0.06 μm
Grain boundary angle: 15°
Crystal information of KNN: The space group and lattice constant were determined by the X-ray diffraction method, and the information shown in Table 1 below was used.
Analysis method: To remove noise, perform cleanup processing, create a grain boundary map under the condition of a grain boundary angle of 15° (a boundary with a crystal orientation difference of 15° or more is regarded as a grain boundary), and analyze the grain size. bottom. When voids or the like existed, a threshold was set for the IQ (Image Quality) value. The area and particle diameter (equivalent circle diameter) of each particle were calculated using the EBSD Number method and Area Fraction method, and the number average particle diameter and area average particle diameter were obtained. When calculating the particle size, particles of 0.20 μm or more were used as the object of calculation in order to remove the part where the crystallinity was poor and the analysis was impossible and the microcrystals as noise.

<Porosity and pore diameter of target material>
Sample preparation: Conducted by the polishing method (After polishing with water-resistant abrasive paper, buffing was performed until there were no large scratches that interfered with the evaluation.)
Apparatus: Ultra-high resolution field emission scanning electron microscope SU-8000 manufactured by Hitachi High-Tech Co., Ltd.
Measurement magnification: 5000 times Analysis method: Using the image analysis software “Adobe Photoshop (registered trademark)” for the SEM image obtained with the above equipment and conditions, binarization of the void part and the matrix phase is performed, and the void to the measurement area is performed. The area ratio of the part was calculated, and the porosity was calculated. Further, the area of each void was calculated using the image operation software "ScnImage", and the diameter of each void (equivalent circle diameter) was calculated assuming that the shape was an equivalent circle. The average diameter of the voids was obtained by calculating the equivalent circle diameter from the area when the cumulative area was 50% of the calculated total area of the voids. As for the maximum diameter of the voids, the maximum value was extracted from the calculated void diameters.

<Vickers hardness>
The Vickers hardness of the target materials of Examples and Comparative Examples was measured using the following equipment, conditions and methods.
Equipment: Mitutoyo Micro Vickers Hardness Tester HM-114
Atmosphere: Air Temperature: Room temperature (25°C)
Test force: 1.0 kgf
Load application speed: 10 μm/s
Holding time: 15 sec
Number of measurement points: 5 points
Test method: This test complies with JIS R 1610, using a Vickers indenter (a quadrangular pyramid indenter with a square bottom in which the angle formed by two opposing surfaces is 136 degrees), when an indentation is made on the test surface. Vickers hardness was obtained from the test force of , and the surface area of the depression obtained from the diagonal length of the depression, and the average was obtained from the five measurement results.

<Bending strength>
The bending strength of the target materials of Examples and Comparative Examples was measured using the following apparatus, conditions, and methods.
Apparatus: Universal testing machine 5582 type (load cell 500N) manufactured by Instron
Atmosphere: Air Temperature: Room temperature (25°C)
Test speed: 0.5mm/min
Distance between fulcrums: L = 30mm
Jig material: SiC
Test method: Based on JIS R 1601, evaluated by a three-point bending test. A test piece (size: 3 mm x 4 mm x 40 mm) is placed on two fulcrums placed at a certain distance (30 mm), and a load is applied to one point in the center between the fulcrums to break. I asked for it.

<Relative Density>
The relative densities of the target materials of Examples and Comparative Examples were measured using the following apparatus and method.
Equipment: Alpha Mirage electronic hydrometer MDS300
Test method: A target material cut into a predetermined size was measured for density by the Archimedes method using the apparatus described above. Relative density (%) (=actual density/theoretical density×100) was obtained by dividing the obtained density by the theoretical density of KNN (4.52 g/cm ³ ).

<Insulation evaluation>
The insulating properties of the target materials of Examples and Comparative Examples were evaluated by measuring the volume resistivity using the following apparatus, test, and method.
Apparatus: Mitani Micronics Co., Ltd. screen printing machine MODEL MEC = 2400E type Nishiyama Seisakusho Co., Ltd. resistivity measuring device ADC Co., Ltd. digital ultra-high resistance/micro current meter model 5450
Test method: DC three-terminal method Measurement temperature: Room temperature (25°C)
Measurement atmosphere: argon atmosphere (using 99.9999% pure Ar, flow rate 300 cc/min)
Measurement method: Using a screen printer and platinum paste manufactured by Tanaka Kikinzoku Kogyo Co., Ltd., a main electrode and a guard electrode 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 a platinum paste printed on a sample at 150° C. for 12 hours, followed by baking treatment (Ar atmosphere, 1000° C.) using an atmospheric tubular furnace. After holding the sample with the electrodes in a room temperature (25°C) environment for 15 minutes, apply a DC voltage of 100 V, measure the current after charging for 1 minute, determine the volume resistance of the sample, and determine the thickness and electrode area of the sample. The volume resistivity was calculated from

<BET specific surface area of KNN raw material powder>
The BET specific surface area of the KNN raw material powder obtained in Production Example was measured by the BET one-point method by nitrogen adsorption using a specific surface area measuring device (Monosorb, manufactured by Quantachrome Instruments).

[Production of KNN raw material powder 1]
<Production Example 1>
K ₂ CO ₃ powder, Na ₂ CO ₃ powder, and Nb ₂ O ₅ powder were prepared as starting raw material powders, and 32.5 mol% of sodium and potassium in terms of atoms were prepared by the method described in JP-A-2018-197181. 17.5 mol%, niobium 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. The KNN raw material powder 1 in which K, Na, and Nb are solid-dissolved was obtained by mixing the raw material powder, firing at 650° C. for 7 hours, and pulverizing. After acid dissolution, the composition of the obtained KNN raw material powder 1 was measured by a high-frequency inductively coupled plasma emission spectrometer to confirm that it was almost the same as the preparation ratio. A solid solution was confirmed. Also, the BET specific surface area of the KNN raw material powder 1 was 6.9 m ² /g.

[Production of KNN raw material powder 2]
<Production Example 2>
KNN raw material powder 1 obtained in Production Example 1 was fired in an electric furnace at 750° C. for 5 hours and then at 1000° C. for 5 hours to obtain KNN raw material powder 2 . The BET specific surface area of the obtained KNN raw material powder 2 was 3.3 m ² /g.

[Production of KNN raw material powder 3]
<Production Example 3>
KNN raw material powder 1 obtained in Production Example 1 was fired in an electric furnace at 750° C. for 5 hours and then at 900° 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 3.6 m ² /g.

[Production of KNN raw material powder 4]
<Production Example 4>
K ₂ CO ₃ powder, Na ₂ CO ₃ powder, and Nb ₂ O ₅ powder were prepared as starting raw material powders, and the value of [K/(K+Na)] was 0.35, and the value of [(Na+K)/Nb] was 1. .00, MnO powder and CuO powder are mixed so as to contain Mn and Cu at a predetermined concentration, baked at 650 ° C. for 7 hours, and then pulverized to obtain K, Na, Nb A KNN raw material powder 4 in which is solid-dissolved was obtained. The composition of the obtained KNN raw material powder 4 was measured by a high-frequency inductively coupled plasma emission spectrometer after acid dissolution, confirmed that it was almost the same as the preparation ratio, and by X-ray diffraction analysis, K, Na, Nb A solid solution was confirmed. Further, the BET specific surface area of the KNN raw material powder 4 was 6.9 m ² /g.

[Example 1]
After the KNN raw material powder 2 obtained in Production Example 2 was heated to 200 ° C. and dried, a graphite die of φ 170 mm × φ 101.6 mm × t 100 mm and a graphite punch of φ 101.6 mm × t 65 mm pulse electrification. It was set in a pressure sintering device SPS9.40MK-VII (manufactured by SPS Syntex Co., Ltd.). In a vacuum atmosphere (atmospheric pressure is less than 10 Pa), heating by discharge plasma was started under pressure of 10 MPa, and the temperature was raised from 25° C. to 900° C. at a rate of 50° C./min. During this time, it was confirmed that the gas components desorbed and the atmospheric pressure increased. After gradually increasing the pressure to 30 MPa, the temperature was raised to 1020° C. at 10° C./min and held at 1020° C. for 75 minutes. Thereafter, the energization and pressurization were stopped, and cooling was performed to obtain a disk-shaped target material (a KNN sintered body, a low-insulating target material) having a diameter of about 101 mm and a thickness of 5 mm.

In addition, the obtained target material was subjected to oxidation treatment at 900 ° C. for 5 hours in the atmosphere, and then the surface was ground and finished to obtain a KNN target material (highly insulating target material) with a diameter of 100 mm and a thickness of 5 mm. got

The obtained target material had a number average particle size of 0.60 μm and an area average particle size of 1.05 μm.

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

<Conditions for low pressure SPS>
Mechanical pressure: 10MPa
Heating temperature: ~900°C
Atmospheric pressure (pressure in the chamber): less than 10 Pa (30 Pa when rising)

<Conditions in this pressurized SPS>
Mechanical pressure: 30 MPa (pressurization started at 900 ° C.)
Heating temperature: 1020° C. (increase temperature from 900° C. at 10° C./min, hold for 75 minutes after reaching 1020° C.)
Atmospheric pressure (pressure in chamber): less than 10 Pa

[Example 2]
A KNN target material having 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 main pressure SPS was performed under the conditions shown below.

The obtained target material had a number average particle size of 0.49 μm and an area average particle size of 0.71 μm.

<Conditions in this pressurized SPS>
Mechanical pressure: 40 MPa (pressurization started at 900 ° C.)
Heating temperature: 900 to 1010°C (heating from 900°C to 1010°C at 2.5°C/min, no holding time)
Atmospheric pressure (pressure in chamber): less than 10 Pa

[Comparative Example 1]
A KNN target with a diameter of 100 mm and a thickness of 5 mm was prepared 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 low pressure SPS and the main pressure SPS were performed under the conditions shown below. got the wood.

<Conditions for low pressure SPS>
Mechanical pressure: 10MPa
Heating temperature: 400 ° C. (After heating from 25 ° C. to 400 ° C. at 13 ° C./min, hold for 60 minutes)
Atmospheric pressure (pressure in the chamber): less than 10 Pa (20 Pa when rising)

<Conditions in this pressurized SPS>
Mechanical pressure: 40 MPa (pressurization started at 400 ° C.)
Heating temperature: ~910°C (After heating from 400°C to 800°C at 4°C/min, heating to 910°C at 1.2°C/min and holding for 10 minutes)
Atmospheric pressure (pressure in chamber): less than 10 Pa

[Comparative Example 2]
A diameter of 100 mm and a thickness of A 5 mm KNN target material was obtained.

<Conditions for low pressure SPS>
No implementation

<Conditions in this pressurized SPS>
Mechanical pressure: 40 MPa (pressurization started at 25 ° C.)
Heating temperature: 800 ° C. (After heating from 25 ° C. to 800 ° C. at 50 ° C./min, hold for 160 minutes)
Atmospheric pressure (pressure in the chamber): less than 10 Pa (30 Pa when rising)

<Evaluation regarding voids>
The sputtering surfaces of the target materials produced in Examples 1 and 2 and Comparative Examples 1 and 2 were observed by SEM, and the porosity (%), which is the ratio of the total area of the voids present in the sputtering surface, The average diameter (μm) and maximum diameter (μm) of the voids were measured.

In addition, the Vickers hardness, relative density, and bending strength of Examples 1 and 2 and Comparative Examples 1 and 2 were measured.

Regarding Vickers hardness and relative density, respectively, the state before oxidation treatment (the volume resistivity at 25 ° C. is less than 6.0 × 10 ¹¹ Ω cm) and the state after oxidation treatment (volume resistance at 25 ° C. The measurement was performed at two timings when the ratio is 6.0×10 ¹¹ Ω·cm or more). The target materials obtained in Examples and Comparative Examples each had a volume resistivity of less than 6.0×10 ¹¹ Ω·cm at 25° C. before oxidation, and a volume resistivity at 25° C. after oxidation. The resistivity was 6.0×10 ¹¹ Ω·cm or more. The bending strength was measured after the oxidation treatment. It should be noted that the bending strength does not change due to the oxidation treatment, or slightly decreases due to the removal of carbon as an impurity from the sintered body, so the bending strength before the oxidation treatment is It is more than the bending strength of

These measurement results are shown in Table 1.

In Examples 1 and 2, it can be confirmed that the porosity is 12.0% or less, the average diameter of the pores is 0.60 μm or less, and the maximum diameter of the pores is 1.0 μm or less. rice field.

In Examples 1 and 2, it was confirmed that the Vickers hardness was 460 or more before the oxidation treatment and 250 or more after the oxidation treatment. Moreover, in Examples 1 and 2, it was confirmed that the bending strength was 90 MPa or more in the state after the oxidation treatment. From this, it could be inferred that both Examples 1 and 2 had a bending strength of 90 MPa or more even before the oxidation treatment. In Examples 1 and 2, since these mechanical strength characteristics are provided, it was confirmed that cracks and chips did not occur during grinding and during the subsequent sputtering film forming process. .

In addition, when the Vickers hardness before and after the oxidation treatment was compared for Examples 1 and 2, there was no significant change in these values, and the Vickers hardness after the heat treatment (oxidation treatment) was the Vickers hardness before the heat treatment. , it was confirmed that the size was maintained in excess of 50%.

In addition, when the relative densities before and after the oxidation treatment were compared for Examples 1 and 2, there was no significant change in these values, and the relative density after the heat treatment (oxidation treatment) was the relative density before the heat treatment. , it was confirmed that the size was maintained in excess of 95%.

On the other hand, in Comparative Examples 1 and 2, the porosity is more than 12.0%, or the flat gap diameter of the gap is more than 0.60 μm, and the maximum diameter of the gap is also the same as that of Examples 1 and 2. I was able to confirm that it was bigger than them.

In Comparative Examples 1 and 2, it was confirmed that the Vickers hardness was less than 460 before the oxidation treatment and less than 250 after the oxidation treatment. Moreover, in Comparative Examples 1 and 2, it was confirmed that the bending strength was less than 90 MPa after the oxidation treatment. From this, in Comparative Examples 1 and 2, it was inferred that the bending strength was less than 90 MPa even before the oxidation treatment. In Comparative Examples 2 and 3, it was confirmed that cracks and chips occurred both during grinding and during the subsequent sputtering film forming process.

In addition, when the Vickers hardness before and after the oxidation treatment was compared for Comparative Examples 1 and 2, these values changed greatly, and the Vickers hardness after the heat treatment (oxidation treatment) was the same as the Vickers hardness before the heat treatment. It was confirmed that the hardness was reduced to 50% or less of the hardness.

In addition, when the relative densities before and after the oxidation treatment were compared for Comparative Examples 1 and 2, these values also changed relatively greatly, and the relative density after the heat treatment (oxidation treatment) was the same as before the heat treatment. It has been confirmed that the relative density of 1 is reduced to 95% or less.

<Preferred Embodiment of the Present Disclosure>
Preferred aspects of the present disclosure will be added below.

(Appendix 1)
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,
The ratio of the total area of voids per unit area of the sputtering surface is 12.0% or less,
A sputtering target material is provided in which the average diameter of voids present on the sputtering surface is 0.60 μm or less.

(Appendix 2)
Preferably,
The maximum diameter of voids existing on the sputtering surface is 1.0 μm or less.

(Appendix 3)
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,
A volume resistivity at 25° C. of less than 6.0×10 ¹¹ Ω·cm,
A sputtering target material having a Vickers hardness of 460 or more and a bending strength of 90 MPa or more is provided.

(Appendix 4)
According to yet another aspect of the present disclosure,
A sputtering target material made of a sintered body of an oxide containing potassium, sodium, niobium, and oxygen,
A volume resistivity at 25° C. of 6.0×10 ¹¹ Ω·cm or more,
A sputtering target material having a Vickers hardness of 250 or more and a bending strength of 90 MPa or more is provided.

(Appendix 5)
Preferably,
The Vickers hardness after heat treatment at 900° C. for 5 hours in air is maintained at a level exceeding 50% of the Vickers hardness before heat treatment.

(Appendix 6)
Preferably,
The relative density after heat treatment at 900° C. for 5 hours in air is maintained at a level exceeding 95% of the relative density before the heat treatment.

(Appendix 7)
Preferably,
As dopants, 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, at least one selected from the group consisting of Ga Contains elements.

(Appendix 8)
Preferably,
The main surface has an area of 4500 mm ² or more.

(Appendix 9)
According to yet another aspect of the present disclosure,
The sputtering target material according to any one of Appendices 1 to 8,
a backing plate bonded to the sputtering target material;
A sputtering target is provided comprising:

10 target material 10s sputtering surface

Claims (5)

A sputtering target material made of a sintered body of an oxide containing potassium, sodium, niobium, and oxygen,
The ratio of the total area of voids per unit area of the sputtering surface is 12.0% or less,
A sputtering target material, wherein an average diameter of voids present on the sputtering surface is 0.60 μm or less. The sputtering target material according to claim 1, wherein the maximum diameter of voids present on the sputtering surface is 1.0 µm or less. As dopants, 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, at least one selected from the group consisting of Ga The sputtering target material according to claim 1 or 2, comprising an element. The sputtering target material according to any one of claims 1 to 3, wherein the main surface has an area of 4500 mm ² or more. 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 comprising:

Images