Polycrystalline material containing yttrium aluminum perovskite and method for producing the same

Abstract

Novel polycrystalline materials having yttrium aluminum perovskite (YAP) and yttrium zirconate (YZ) are described. In one embodiment, the polycrystalline material (e.g., bulk or monolithic polycrystalline material) may comprise (a) at least 50 wt% of a yttrium aluminum perovskite (YAP) phase and (b) at least 0.1 wt% of a yttrium zirconate (YZ) phase. Such polycrystalline materials can achieve improved combinations of properties, such as two or more improved combinations of density, fracture modulus (MOR), fracture toughness, dielectric strength, loss tangent, and plasma etching resistance.

Description

【Background Art】 【0001】 <Reference to Related Applications> This patent application claims priority to U.S. Provisional Patent Application No. 63 / 470,021, filed May 31, 2023, entitled "POLYCRYSTALLINE MATERIALS COMPRISING YTTRIUM ALUMINUM PEROVSKITE AND METHODS OF MAKING THE SAME", which is hereby incorporated by reference in its entirety. 【0002】 <Background> As described in U.S. Patent Application Publication No. 2021 / 0221742, ceramic materials can be used to form structures that are transmissive to electromagnetic radiation of various wavelengths. However, some ceramic materials may not have sufficient structural integrity to withstand extreme forces or temperatures. Additionally, when a ceramic material contains multiple materials, the refractive index mismatch of each material can affect the transmissivity and emittance of the ceramic material. 【Summary of the Invention】 【0003】 <Summary of the Disclosure> Generally, this patent application relates to novel polycrystalline materials comprising yttrium aluminum perovskite (YAP) and yttrium zirconate (YZ) and methods of making the same. In one aspect, a polycrystalline material (e.g., a bulk polycrystalline material or a monolithic polycrystalline material) can include (a) at least 50 wt% of a yttrium aluminum perovskite (YAP) phase, and (b) at least 0.1 wt% of a yttrium zirconate (YZ) phase. Such polycrystalline materials can achieve a combination of improved properties such as an improved combination of two or more of density, modulus of rupture (MOR), fracture toughness, dielectric strength, loss tangent, and plasma etch resistance. Further details are provided below. 【0004】 [i. Composition of polycrystalline materials] As described above, novel polycrystalline materials generally consist of (a) at least 50 wt% yttrium aluminum perovskite (YAP) phase (YAlO3) and (b) at least 0.1 wt% yttrium zirconate (YZ) phase (Y4Zr3O3). 12 ) include (and consist of or essentially consist of). With respect to the YZ phase, in one embodiment, the novel polycrystalline material contains at least 0.2 wt% of the YZ phase. In another embodiment, the novel polycrystalline material contains at least 0.3 wt% of the YZ phase. In yet another embodiment, the novel polycrystalline material contains at least 0.4 wt% of the YZ phase. In another embodiment, the novel polycrystalline material contains at least 0.5 wt% of the YZ phase. In yet another embodiment, the novel polycrystalline material contains at least 0.6 wt% of the YZ phase. In another embodiment, the novel polycrystalline material contains at least 0.7 wt% of the YZ phase. In yet another embodiment, the novel polycrystalline material contains at least 0.8 wt% of the YZ phase. In another embodiment, the novel polycrystalline material contains at least 0.9 wt% of the YZ phase. In yet another embodiment, the novel polycrystalline material contains at least 1.0 wt% of the YZ phase. In yet another embodiment, the novel polycrystalline material contains at least 1.2 wt% of the YZ phase. In yet another embodiment, the novel polycrystalline material contains at least 1.4 wt% of the YZ phase. In yet another embodiment, the novel polycrystalline material contains at least 1.6 wt% of the YZ phase. In yet another embodiment, the novel polycrystalline material contains at least 1.8 wt% of the YZ phase. In yet another embodiment, the novel polycrystalline material contains at least 2.0 wt% of the YZ phase. In yet another embodiment, the novel polycrystalline material contains at least 2.2 wt% of the YZ phase. In yet another embodiment, the novel polycrystalline material contains at least 2.4 wt% of the YZ phase. In yet another embodiment, the novel polycrystalline material contains at least 2.6 wt% of the YZ phase. In yet another embodiment, the novel polycrystalline material contains at least 2.8 wt% of the YZ phase. In yet another embodiment, the novel polycrystalline material contains at least 3.0 wt% of the YZ phase. 【0005】 In one embodiment, the novel polycrystalline material contains 10.0% by weight or less of the YZ phase. In another embodiment, the novel polycrystalline material contains 9.0% by weight or less of the YZ phase. In yet another embodiment, the novel polycrystalline material contains 8.0% by weight or less of the YZ phase. In yet another embodiment, the novel polycrystalline material contains 7.0% by weight or less of the YZ phase. In yet another embodiment, the novel polycrystalline material contains 6.0% by weight or less of the YZ phase. In yet another embodiment, the novel polycrystalline material contains 5.0% by weight or less of the YZ phase. In yet another embodiment, the novel polycrystalline material contains 4.0% by weight or less of the YZ phase. In yet another embodiment, the novel polycrystalline material contains 3.0% by weight or less of the YZ phase. In yet another embodiment, the novel polycrystalline material contains 2.0% by weight or less of the YZ phase. In yet another embodiment, the novel polycrystalline material contains 1.0% by weight or less of the YZ phase. 【0006】 As described above, the novel polycrystalline material generally contains at least 50 wt% of yttrium aluminum perovskite (YAP) phase. In one embodiment, the novel polycrystalline material contains at least 55 wt% of YAP phase. In another embodiment, the novel polycrystalline material contains at least 60 wt% of YAP phase. In yet another embodiment, the novel polycrystalline material contains at least 65 wt% of YAP phase. In another embodiment, the novel polycrystalline material contains at least 70 wt% of YAP phase. In yet another embodiment, the novel polycrystalline material contains at least 75 wt% of YAP phase. In another embodiment, the novel polycrystalline material contains at least 80 wt% of YAP phase. In yet another embodiment, the novel polycrystalline material contains at least 82 wt% of YAP phase. In another embodiment, the novel polycrystalline material contains at least 84 wt% of YAP phase. In yet another embodiment, the novel polycrystalline material contains at least 86 wt% of YAP phase. In another embodiment, the novel polycrystalline material contains at least 88% by weight of the YAP phase. In yet another embodiment, the novel polycrystalline material contains at least 90% by weight of the YAP phase. In another embodiment, the novel polycrystalline material contains at least 92% by weight of the YAP phase. In yet another embodiment, the novel polycrystalline material contains at least 94% by weight of the YAP phase. In another embodiment, the novel polycrystalline material contains at least 95% by weight of the YAP phase. In yet another embodiment, the novel polycrystalline material contains at least 96% by weight of the YAP phase. In another embodiment, the novel polycrystalline material contains at least 97% by weight of the YAP phase. In yet another embodiment, the novel polycrystalline material contains at least 98% by weight of the YAP phase. In another embodiment, the novel polycrystalline material contains at least 99% by weight of the YAP phase. 【0007】 Novel polycrystalline materials may contain limited amounts of other crystalline phases. For example, novel polycrystalline materials may contain limited amounts of yttrium aluminum garnet (YAG) phase, yttrium aluminum monoclinic (YAM) phase, yttria phase, and alumina phase. 【0008】 Yttrium aluminum garnet (YAG) phase (Y3Al5O 12Regarding this, in one method, the novel polycrystalline material may contain 0.1 to 49.9% by weight of the YAG phase. In one embodiment, the novel polycrystalline material contains at least 1% by weight of the YAG phase. In another embodiment, the novel polycrystalline material contains at least 2% by weight of the YAG phase. In yet another embodiment, the novel polycrystalline material contains at least 3% by weight of the YAG phase. In another embodiment, the novel polycrystalline material contains at least 4% by weight of the YAG phase. In yet another embodiment, the novel polycrystalline material contains at least 5% by weight of the YAG phase. In another embodiment, the novel polycrystalline material contains at least 6% by weight of the YAG phase. In yet another embodiment, the novel polycrystalline material contains at least 7% by weight of the YAG phase. In another embodiment, the novel polycrystalline material contains at least 8% by weight of the YAG phase. In yet another embodiment, the novel polycrystalline material contains at least 9% by weight of the YAG phase. In yet another embodiment, the novel polycrystalline material contains at least 10% by weight of the YAG phase. In yet another embodiment, the novel polycrystalline material contains at least 11 wt% of the YAG phase. In yet another embodiment, the novel polycrystalline material contains at least 12 wt% of the YAG phase. In yet another embodiment, the novel polycrystalline material contains at least 13 wt% of the YAG phase. In yet another embodiment, the novel polycrystalline material contains at least 14 wt% of the YAG phase. In yet another embodiment, the novel polycrystalline material contains at least 15 wt% of the YAG phase. In yet another embodiment, the novel polycrystalline material contains at least 16 wt% of the YAG phase. In yet another embodiment, the novel polycrystalline material contains at least 17 wt% of the YAG phase. In yet another embodiment, the novel polycrystalline material contains at least 18 wt% of the YAG phase. In yet another embodiment, the novel polycrystalline material contains at least 19 wt% of the YAG phase. In yet another embodiment, the novel polycrystalline material contains at least 20 wt% of the YAG phase. In yet another embodiment, the novel polycrystalline material contains at least 21 wt% of the YAG phase. In another embodiment, the novel polycrystalline material contains at least 22% by weight of the YAG phase. In yet another embodiment, the novel polycrystalline material contains at least 23% by weight of the YAG phase.In other embodiments, the novel polycrystalline material contains at least 24% by weight of the YAG phase. 【0009】 In one embodiment, the novel polycrystalline material contains 45% by weight or less of YAG phase. In another embodiment, the novel polycrystalline material contains 40% by weight or less of YAG phase. In yet another embodiment, the novel polycrystalline material contains 38% by weight or less of YAG phase. In another embodiment, the novel polycrystalline material contains 36% by weight or less of YAG phase. In yet another embodiment, the novel polycrystalline material contains 34% by weight or less of YAG phase. In another embodiment, the novel polycrystalline material contains 32% by weight or less of YAG phase. In yet another embodiment, the novel polycrystalline material contains 30% by weight or less of YAG phase. In another embodiment, the novel polycrystalline material contains 28% by weight or less of YAG phase. In yet another embodiment, the novel polycrystalline material contains 26% by weight or less of YAG phase. In another embodiment, the novel polycrystalline material contains 24% by weight or less of YAG phase. In yet another embodiment, the novel polycrystalline material contains 22% by weight or less of YAG phase. In yet another embodiment, the novel polycrystalline material contains 20% by weight or less of YAG phase. In other embodiments, the novel polycrystalline material contains 18% by weight or less of the YAG phase. In yet another embodiment, the novel polycrystalline material contains 16% by weight or less of the YAG phase. In other embodiments, the novel polycrystalline material contains 14% by weight or less of the YAG phase. In yet another embodiment, the novel polycrystalline material contains 12% by weight or less of the YAG phase. In other embodiments, the novel polycrystalline material contains 10% by weight or less of the YAG phase. In yet another embodiment, the novel polycrystalline material contains 8% by weight or less of the YAG phase. In other embodiments, the novel polycrystalline material contains 6% by weight or less of the YAG phase. In yet another embodiment, the novel polycrystalline material contains 5% by weight or less of the YAG phase. In other embodiments, the novel polycrystalline material contains 4% by weight or less of the YAG phase. In yet another embodiment, the novel polycrystalline material contains 3% by weight or less of the YAG phase. In other embodiments, the novel polycrystalline material contains 2% by weight or less of the YAG phase. In yet another embodiment, the novel polycrystalline material contains 1% by weight or less of the YAG phase. In other embodiments, the novel polycrystalline material contains 0.5% by weight or less of the YAG phase. 【0010】 In one approach, the YAG phase is present only as an impurity in the novel polycrystalline material. 【0011】 With respect to the yttrium aluminum monoclinic (YAM) phase (Y4Al2O9), in one embodiment, the novel polycrystalline material contains 45% by weight or less of the YAM phase. In another embodiment, the novel polycrystalline material contains 40% by weight or less of the YAM phase. In yet another embodiment, the novel polycrystalline material contains 38% by weight or less of the YAM phase. In yet another embodiment, the novel polycrystalline material contains 36% by weight or less of the YAM phase. In yet another embodiment, the novel polycrystalline material contains 34% by weight or less of the YAM phase. In yet another embodiment, the novel polycrystalline material contains 32% by weight or less of the YAM phase. In yet another embodiment, the novel polycrystalline material contains 30% by weight or less of the YAM phase. In yet another embodiment, the novel polycrystalline material contains 28% by weight or less of the YAM phase. In yet another embodiment, the novel polycrystalline material contains 26% by weight or less of the YAM phase. In yet another embodiment, the novel polycrystalline material contains 24% by weight or less of the YAM phase. In yet another embodiment, the novel polycrystalline material contains 22% by weight or less of the YAM phase. In yet another embodiment, the novel polycrystalline material contains 20% by weight or less of the YAM phase. In yet another embodiment, the novel polycrystalline material contains 18% by weight or less of the YAM phase. In yet another embodiment, the novel polycrystalline material contains 16% by weight or less of the YAM phase. In yet another embodiment, the novel polycrystalline material contains 14% by weight or less of the YAM phase. In yet another embodiment, the novel polycrystalline material contains 12% by weight or less of the YAM phase. In yet another embodiment, the novel polycrystalline material contains 10% by weight or less of the YAM phase. In yet another embodiment, the novel polycrystalline material contains 8% by weight or less of the YAM phase. In yet another embodiment, the novel polycrystalline material contains 6% by weight or less of the YAM phase. In yet another embodiment, the novel polycrystalline material contains 5% by weight or less of the YAM phase. In yet another embodiment, the novel polycrystalline material contains 4% by weight or less of the YAM phase. In yet another embodiment, the novel polycrystalline material contains 3% by weight or less of the YAM phase. In other embodiments, the novel polycrystalline material contains 2% by weight or less of the YAM phase. In yet another embodiment, the novel polycrystalline material contains 1% by weight or less of the YAM phase. In yet another embodiment, the novel polycrystalline material contains 0.5% by weight or less of the YAM phase. 【0012】 In one approach, the YAM phase is present only as an impurity in novel polycrystalline materials. 【0013】 As described above, the novel polycrystalline material may contain a limited amount of yttria (Y2O3) phase. In one embodiment, the novel polycrystalline material contains 10% by weight or less of yttria phase. In another embodiment, the novel polycrystalline material contains 8% by weight or less of yttria phase. In yet another embodiment, the novel polycrystalline material contains 6% by weight or less of yttria phase. In yet another embodiment, the novel polycrystalline material contains 5% by weight or less of yttria phase. In yet another embodiment, the novel polycrystalline material contains 4% by weight or less of yttria phase. In yet another embodiment, the novel polycrystalline material contains 3% by weight or less of yttria phase. In yet another embodiment, the novel polycrystalline material contains 2% by weight or less of yttria phase. In yet another embodiment, the novel polycrystalline material contains 1% by weight or less of yttria phase. In yet another embodiment, the novel polycrystalline material contains 0.5% by weight or less of yttria phase. In yet another embodiment, the novel polycrystalline material contains 0.25% by weight or less of yttria phase. In yet another embodiment, the novel polycrystalline material contains 0.1% by weight or less of yttria phase. 【0014】 In one approach, the yttria phase is present only as an impurity in novel polycrystalline materials. 【0015】 As described above, the novel polycrystalline material may contain a limited amount of alumina (Al2O3) phase. In one embodiment, the novel polycrystalline material contains 10% by weight or less of alumina phase. In another embodiment, the novel polycrystalline material contains 8% by weight or less of alumina phase. In yet another embodiment, the novel polycrystalline material contains 6% by weight or less of alumina phase. In another embodiment, the novel polycrystalline material contains 5% by weight or less of alumina phase. In yet another embodiment, the novel polycrystalline material contains 4% by weight or less of alumina phase. In another embodiment, the novel polycrystalline material contains 3% by weight or less of alumina phase. In yet another embodiment, the novel polycrystalline material contains 2% by weight or less of alumina phase. In another embodiment, the novel polycrystalline material contains 1% by weight or less of alumina phase. In yet another embodiment, the novel polycrystalline material contains 0.5% by weight or less of alumina phase. In yet another embodiment, the novel polycrystalline material contains 0.25% by weight or less of alumina phase. In yet another embodiment, the novel polycrystalline material contains 0.1% by weight or less of an alumina phase. 【0016】 In one method, the alumina phase is present only as an impurity in the novel polycrystalline material. [ii. Microstructure] 【0017】 As described above, novel polycrystalline materials can achieve improved combinations of properties, such as improved combinations of two or more of the following: density, modulus of fracture (MOR), fracture toughness, dielectric strength, loss tangent, and plasma etching resistance. Such properties can be achieved, for example, by the microstructure unique to the novel polycrystalline material. 【0018】 In one embodiment, the novel polycrystalline material achieves an average particle size of 30 micrometers or less. In another embodiment, the novel polycrystalline material achieves an average particle size of 28 micrometers or less. In yet another embodiment, the novel polycrystalline material achieves an average particle size of 26 micrometers or less. In another embodiment, the novel polycrystalline material achieves an average particle size of 24 micrometers or less. In yet another embodiment, the novel polycrystalline material achieves an average particle size of 22 micrometers or less. In another embodiment, the novel polycrystalline material achieves an average particle size of 20 micrometers or less. In yet another embodiment, the novel polycrystalline material achieves an average particle size of 18 micrometers or less. In another embodiment, the novel polycrystalline material achieves an average particle size of 16 micrometers or less. In yet another embodiment, the novel polycrystalline material achieves an average particle size of 14 micrometers or less. In another embodiment, the novel polycrystalline material achieves an average particle size of 12 micrometers or less. In yet another embodiment, the novel polycrystalline material achieves an average particle size of 10 micrometers or less. In yet another embodiment, the novel polycrystalline material achieves an average particle size of 8 micrometers or less. In yet another embodiment, the novel polycrystalline material achieves an average grain size of 6 micrometers or less. In yet another embodiment, the novel polycrystalline material achieves an average grain size of 5 micrometers or less. In yet another embodiment, the novel polycrystalline material achieves an average grain size of 4 micrometers or less. In yet another embodiment, the novel polycrystalline material achieves an average grain size of 3 micrometers or less. In yet another embodiment, the novel polycrystalline material achieves an average grain size of 2 micrometers or less. 【0019】 In one embodiment, the novel polycrystalline material achieves a maximum particle size of 80 micrometers or less. In another embodiment, the novel polycrystalline material achieves a maximum particle size of 70 micrometers or less. In yet another embodiment, the novel polycrystalline material achieves a maximum particle size of 60 micrometers or less. In yet another embodiment, the novel polycrystalline material achieves a maximum particle size of 50 micrometers or less. In yet another embodiment, the novel polycrystalline material achieves a maximum particle size of 40 micrometers or less. In yet another embodiment, the novel polycrystalline material achieves a maximum particle size of 30 micrometers or less. In yet another embodiment, the novel polycrystalline material achieves a maximum particle size of 25 micrometers or less. In yet another embodiment, the novel polycrystalline material achieves a maximum particle size of 20 micrometers or less. In yet another embodiment, the novel polycrystalline material achieves a maximum particle size of 18 micrometers or less. In yet another embodiment, the novel polycrystalline material achieves a maximum particle size of 16 micrometers or less. In yet another embodiment, the novel polycrystalline material achieves a maximum particle size of 14 micrometers or less. In yet another embodiment, the novel polycrystalline material achieves a maximum particle size of 12 micrometers or less. In yet another embodiment, the novel polycrystalline material achieves a maximum particle size of 10 micrometers or less. In yet another embodiment, the novel polycrystalline material achieves a maximum particle size of 9 micrometers or less. In yet another embodiment, the novel polycrystalline material achieves a maximum particle size of 8 micrometers or less. In yet another embodiment, the novel polycrystalline material achieves a maximum particle size of 7 micrometers or less. In yet another embodiment, the novel polycrystalline material achieves a maximum particle size of 6 micrometers or less. 【0020】 In one embodiment, the novel polycrystalline material contains at least several YZ phase precipitates at the grain boundaries. 【0021】 [iii. Manufacturing method] Novel polycrystalline materials can be manufactured by various methods, such as ceramic powder processing technology. In one embodiment, and referring to Figure 1, method (10) may include the steps of (100) of preparing a green body from a powder containing YAP (YAlO3) and YZ (yttrium zirconate), and (200) of sintering the green body to form a final product. The final product can realize any of the compositions described in the above section (i) of the composition of the polycrystalline material. 【0022】 With respect to the process (100) for producing the green body, this process may include any suitable method for producing the green body, including but not limited to die compaction, isostatic pressing, slip casting, tape casting, extrusion, and injection molding. In one embodiment, the production process (100) is die compaction (e.g., dry pressing for forming a solid compact). 【0023】 With respect to the step (200) of sintering the green body, this step may include heating the green body to any temperature or a series of temperatures sufficient to produce a densified final product. In one embodiment, the sintering temperature is 1200°C to 1900°C. In one embodiment, the sintering time is 0.2 hours to 20 hours. In one embodiment, the sintering is pressureless sintering. In other embodiments, pressure may be applied during sintering. 【0024】 In one embodiment, and referring to Figure 2, method (10') may include the steps of preparing a precursor powder (20) and then preparing a powder containing the YAP (YAlO3) phase and the YZ (yttrium zirconate) phase from the precursor powder (50). The powder containing the YAP (YAlO3) phase and the YZ (yttrium zirconate) phase can then be used to prepare the green as described above. 【0025】 With respect to the step (20) of preparing the precursor powder, method (10') may include blending yttria and alumina to prepare a powder blend (22), and heating the powder blend at a temperature and time sufficient to prepare the precursor powder (24). With respect to the blending step (22), the powder blend may contain 45-50 mol% yttria and 50-55 mol% alumina, but other amounts may be used. As shown in the examples herein, the amounts of yttria and alumina may be pre-selected to achieve a predetermined amount of the desired crystalline phase (e.g., predetermined amounts of YAP, YAG, YAM, YZ, yttria, and / or alumina phases). 【0026】 In one embodiment, the precursor powder contains at least 55% by weight of YAP phase. In another embodiment, the precursor powder contains at least 60% by weight of YAP phase. In yet another embodiment, the precursor powder contains at least 65% by weight of YAP phase. In another embodiment, the precursor powder contains at least 70% by weight of YAP phase. In yet another embodiment, the precursor powder contains at least 75% by weight of YAP phase. In another embodiment, the precursor powder contains at least 80% by weight of YAP phase. In yet another embodiment, the precursor powder contains at least 82% by weight of YAP phase. In another embodiment, the precursor powder contains at least 84% by weight of YAP phase. In yet another embodiment, the precursor powder contains at least 86% by weight of YAP phase. In another embodiment, the precursor powder contains at least 88% by weight of YAP phase. In yet another embodiment, the precursor powder contains at least 90% by weight of YAP phase. In another embodiment, the precursor powder contains at least 92% by weight of YAP phase. In yet another embodiment, the precursor powder contains at least 94% by weight of YAP phase. In yet another embodiment, the precursor powder contains at least 95% by weight of YAP phase. In yet another embodiment, the precursor powder contains at least 96% by weight of YAP phase. In yet another embodiment, the precursor powder contains at least 97% by weight of YAP phase. In yet another embodiment, the precursor powder contains at least 98% by weight of YAP phase. In yet another embodiment, the precursor powder contains at least 99% by weight of YAP phase. 【0027】 In one embodiment, the precursor powder contains 50% by weight or less of YAG phase. In another embodiment, the precursor powder contains 45% by weight or less of YAG phase. In yet another embodiment, the precursor powder contains 40% by weight or less of YAG phase. In another embodiment, the precursor powder contains 35% by weight or less of YAG phase. In yet another embodiment, the precursor powder contains 30% by weight or less of YAG phase. In another embodiment, the precursor powder contains 25% by weight or less of YAG phase. In yet another embodiment, the precursor powder contains 20% by weight or less of YAG phase. In another embodiment, the precursor powder contains 15% by weight or less of YAG phase. In yet another embodiment, the precursor powder contains 10% by weight or less of YAG phase. In another embodiment, the precursor powder contains 5% by weight or less of YAG phase. In yet another embodiment, the precursor powder contains 3% by weight or less of YAG phase. In another embodiment, the precursor powder contains 1% by weight or less of YAG phase. In yet another embodiment, the precursor powder contains 0.5% by weight or less of YAG phase. In yet another embodiment, the precursor powder contains 0.25% by weight or less of YAG phase. In yet another embodiment, the precursor powder contains 0.1% by weight or less of YAG phase. 【0028】 In some embodiments, the precursor powder contains an intentional amount of YAG phase. For example, in one embodiment, the precursor powder may contain at least 0.5% by weight of YAG phase. In other embodiments, the precursor powder may contain at least 1% by weight of YAG phase. 【0029】 In one embodiment, the precursor powder contains 50% by weight or less of YAM phase. In another embodiment, the precursor powder contains 45% by weight or less of YAM phase. In yet another embodiment, the precursor powder contains 40% by weight or less of YAM phase. In another embodiment, the precursor powder contains 35% by weight or less of YAM phase. In yet another embodiment, the precursor powder contains 30% by weight or less of YAM phase. In another embodiment, the precursor powder contains 25% by weight or less of YAM phase. In yet another embodiment, the precursor powder contains 20% by weight or less of YAM phase. In another embodiment, the precursor powder contains 15% by weight or less of YAM phase. In yet another embodiment, the precursor powder contains 10% by weight or less of YAM phase. In another embodiment, the precursor powder contains 5% by weight or less of YAM phase. In yet another embodiment, the precursor powder contains 3% by weight or less of YAM phase. In another embodiment, the precursor powder contains 1% by weight or less of YAM phase. In yet another embodiment, the precursor powder contains 0.5% by weight or less of YAM phase. In yet another embodiment, the precursor powder contains 0.25% by weight or less of YAM phase. In yet another embodiment, the precursor powder contains 0.1% by weight or less of YAM phase. 【0030】 In some embodiments, the precursor powder contains an intentional amount of YAM phase. For example, in one embodiment, the precursor powder may contain at least 0.5% by weight of YAM phase. In other embodiments, the precursor powder may contain at least 1% by weight of YAM phase. 【0031】 In one embodiment, the precursor powder contains 10% by weight or less of yttria phase. In another embodiment, the precursor powder contains 8% by weight or less of yttria phase. In yet another embodiment, the precursor powder contains 6% by weight or less of yttria phase. In another embodiment, the precursor powder contains 5% by weight or less of yttria phase. In yet another embodiment, the precursor powder contains 4% by weight or less of yttria phase. In another embodiment, the precursor powder contains 3% by weight or less of yttria phase. In yet another embodiment, the precursor powder contains 2% by weight or less of yttria phase. In another embodiment, the precursor powder contains 1% by weight or less of yttria phase. In yet another embodiment, the precursor powder contains 0.5% by weight or less of yttria phase. In another embodiment, the precursor powder contains 0.25% by weight or less of yttria phase. In yet another embodiment, the precursor powder contains 0.1% by weight or less of yttria phase. 【0032】 In one embodiment, the precursor powder contains 10% by weight or less of an alumina phase. In another embodiment, the precursor powder contains 8% by weight or less of an alumina phase. In yet another embodiment, the precursor powder contains 6% by weight or less of an alumina phase. In another embodiment, the precursor powder contains 5% by weight or less of an alumina phase. In yet another embodiment, the precursor powder contains 4% by weight or less of an alumina phase. In another embodiment, the precursor powder contains 3% by weight or less of an alumina phase. In yet another embodiment, the precursor powder contains 2% by weight or less of an alumina phase. In another embodiment, the precursor powder contains 1% by weight or less of an alumina phase. In yet another embodiment, the precursor powder contains 0.5% by weight or less of an alumina phase. In another embodiment, the precursor powder contains 0.25% by weight or less of an alumina phase. In yet another embodiment, the precursor powder contains 0.1% by weight or less of an alumina phase. 【0033】 Referring again to Figure 2, the step (20) for preparing the precursor powder may include one or more additional powder processing steps, for example, (a) milling of the powder blend (e.g., attrition milling), (b) screening of the powder blend, (c) preparation of the powder blend for spray drying (e.g., using a suitable binder), and (d) spray drying of the blended powder. The heating step (24) may be performed after the spray drying step. 【0034】 Continuing to refer to Figure 2, the step (50) of preparing a powder containing the YAP(YAlO3) phase and the YZ(yttrium zirconate) phase from the precursor powder may include any suitable powder processing step, for example, one of the following: (a) milling of the precursor powder (e.g., attrition milling), (b) screening of the precursor powder, (c) preparation of the precursor for spray drying (e.g., using a suitable binder), and (d) spray drying of the precursor powder to prepare a final powder containing the YAP(YAlO3) phase and the YZ(yttrium zirconate) phase. The final powder may then be used to prepare the green as described above. 【0035】 In one method, and referring to Figure 3, method (10'') may include a step (52) of introducing zirconium to facilitate the formation of the YZ phase in the final powder. The zirconium can be introduced at any appropriate point in the process of producing the final powder. For example, the zirconium can be introduced during the milling (54) of the precursor powder by milling with a zirconium-containing milling medium (e.g., zirconia milling powder). In such embodiments, the zirconium-containing medium may be considered a transfer material. 【0036】 In some embodiments, zirconium can be introduced by adding a zirconium-containing material, such as zirconium-containing powder, to the precursor powder (56). For example, to facilitate the introduction of zirconium, a zirconium-containing powder (e.g., zirconia powder) may be mixed with the precursor powder. Such mixing may be performed, for example, before, during, or after milling the precursor powder. 【0037】 In some embodiments, zirconium can be introduced by exposing a precursor powder to a liquid (58) containing zirconium. For example, the precursor powder may be in contact with an aqueous solution or organic solution containing zirconium (e.g., zirconium ions). Such contact may be performed, for example, when preparing the precursor powder for spray drying. 【0038】 The amount of zirconium introduced into the precursor powder can be selected based on the desired amount of YZ phase in the final powder. 【0039】 Zirconium may also be introduced during the preparation of the precursor powder. For example, referring to Figure 2, zirconium may be introduced (i) in the yttria powder and alumina powder blend (22), or (ii) during the milling of the yttria powder and alumina powder (for example, by milling with a milling medium containing zirconium). Zirconium may also be introduced, or substituted for, when preparing the powder blend for spray drying by contacting the powder blend with an aqueous solution or organic solution containing zirconium (e.g., zirconium ions). 【0040】 The amount of zirconium introduced into the powder blend can be selected based on the desired amount of YZ phase in the final powder. 【0041】 [iv.Characteristics] As described above, novel polycrystalline materials can achieve improved combinations of properties, such as improved combinations of two or more of the following: density, modulus of fracture (MOR), fracture toughness, dielectric strength, loss tangent, and plasma etching resistance. 【0042】 In one embodiment, the novel polycrystalline material achieves a density of at least 4.5 g / cm 3 In other embodiments, the novel polycrystalline material achieves a density of at least 4.6 g / cm 3 In still other embodiments, the novel polycrystalline material achieves a density of at least 4.7 g / cm 3 In other embodiments, the novel polycrystalline material achieves a density of at least 4.8 g / cm 3 In still other embodiments, the novel polycrystalline material achieves a density of at least 4.9 g / cm 3 In other embodiments, the novel polycrystalline material achieves a density of at least 5.0 g / cm 3 In still other embodiments, the novel polycrystalline material achieves a density of at least 5.05 g / cm 3 In other embodiments, the novel polycrystalline material achieves a density of at least 5.10 g / cm 3 In still other embodiments, the novel polycrystalline material achieves a density of at least 5.15 g / cm 3 In other embodiments, the novel polycrystalline material achieves a density of at least 5.20 g / cm 3 In still other embodiments, the novel polycrystalline material achieves a density of at least 5.22 g / cm 3 In other embodiments, the novel polycrystalline material achieves a density of at least 5.24 g / cm 3 In still other embodiments, the novel polycrystalline material achieves a density of at least 5.26 g / cm 3 In other embodiments, the novel polycrystalline material achieves a density of at least 5.28 g / cm 3 In still other embodiments, the novel polycrystalline material achieves a density of at least 5.30 g / cm 3 In other embodiments, the novel polycrystalline material achieves a density of at least 5.30 g / cm 【0043】 In one embodiment, the novel polycrystalline material achieves a MOR(4-point) strength of at least 200 MPa. In another embodiment, the novel polycrystalline material achieves a MOR(4-point) strength of at least 210 MPa. In yet another embodiment, the novel polycrystalline material achieves a MOR(4-point) strength of at least 220 MPa. In another embodiment, the novel polycrystalline material achieves a MOR(4-point) strength of at least 230 MPa. In yet another embodiment, the novel polycrystalline material achieves a MOR(4-point) strength of at least 240 MPa. In another embodiment, the novel polycrystalline material achieves a MOR(4-point) strength of at least 250 MPa. In yet another embodiment, the novel polycrystalline material achieves a MOR(4-point) strength of at least 260 MPa. In another embodiment, the novel polycrystalline material achieves a MOR(4-point) strength of at least 270 MPa. In yet another embodiment, the novel polycrystalline material achieves a MOR(4-point) strength of at least 280 MPa. In another embodiment, the novel polycrystalline material achieves a MOR(4-point) strength of at least 290 MPa. In yet another embodiment, the novel polycrystalline material achieves a MOR(4-point) strength of at least 300 MPa. In another embodiment, the novel polycrystalline material achieves a MOR(4-point) strength of at least 310 MPa. In yet another embodiment, the novel polycrystalline material achieves a MOR(4-point) strength of at least 320 MPa. In another embodiment, the novel polycrystalline material achieves a MOR(4-point) strength of at least 330 MPa. In yet another embodiment, the novel polycrystalline material achieves a MOR(4-point) strength of at least 340 MPa. In another embodiment, the novel polycrystalline material achieves a MOR(4-point) strength of at least 350 MPa. In yet another embodiment, the novel polycrystalline material achieves a MOR(4-point) strength of at least 360 MPa. In another embodiment, the novel polycrystalline material achieves a MOR(4-point) strength of at least 370 MPa. In yet another embodiment, the novel polycrystalline material achieves a MOR (4-point) strength of at least 380 MPa.In other embodiments, the novel polycrystalline material achieves a MOR(4-point) strength of at least 390 MPa. 【0044】 In one embodiment, the novel polycrystalline material has a pressure of at least 2.0 MPa*m 1 / 2 Plane distortion (K IC ) Achieves fracture toughness. In other embodiments, the novel polycrystalline material has a fracture toughness of at least 2.2 MPa*m 1 / 2 Plane distortion (K IC ) Achieves fracture toughness. In another embodiment, the novel polycrystalline material has a fracture toughness of at least 2.4 MPa*m 1 / 2 Plane distortion (K IC ) Achieves fracture toughness. In other embodiments, the novel polycrystalline material has a fracture toughness of at least 2.6 MPa*m 1 / 2 Plane distortion (K IC ) Achieves fracture toughness. In other embodiments, the novel polycrystalline material has a fracture toughness of at least 2.8 MPa*m 1 / 2 Plane distortion (K IC ) Achieves fracture toughness. In other embodiments, the novel polycrystalline material has a fracture toughness of at least 3.0 MPa*m 1 / 2 Plane distortion (K IC ) Achieves fracture toughness. In further embodiments, the novel polycrystalline material has a fracture toughness of at least 3.2 MPa*m 1 / 2 Plane distortion (K IC ) Achieves fracture toughness. In other embodiments, the novel polycrystalline material has a fracture toughness of at least 3.4 MPa*m 1 / 2 Plane distortion (K IC ) Achieves fracture toughness. In another embodiment, the novel polycrystalline material has a fracture toughness of at least 3.6 MPa*m 1 / 2 Plane distortion (K IC ) Achieves fracture toughness. In other embodiments, the novel polycrystalline material has a fracture toughness of at least 3.8 MPa*m 1 / 2 Plane distortion (K IC ) Achieves fracture toughness. In other embodiments, the novel polycrystalline material has a fracture toughness of at least 4.0 MPa*m 1 / 2 Plane distortion (K IC ) Achieves fracture toughness. In other embodiments, the novel polycrystalline material has a fracture toughness of at least 4.2 MPa*m1 / 2 Plane distortion (K IC ) Achieves fracture toughness. In another embodiment, the novel polycrystalline material has a fracture toughness of at least 4.4 MPa*m 1 / 2 Plane distortion (K IC ) Achieves fracture toughness. In other embodiments, the novel polycrystalline material has a fracture toughness of at least 4.5 MPa*m 1 / 2 Plane distortion (K IC ) Achieves fracture toughness. In another embodiment, the novel polycrystalline material has a fracture toughness of at least 4.6 MPa*m 1 / 2 Plane distortion (K IC ) Achieves fracture toughness. In other embodiments, the novel polycrystalline material has a fracture toughness of at least 4.7 MPa*m 1 / 2 Plane distortion (K IC ) Achieves fracture toughness. In further embodiments, the novel polycrystalline material has a fracture toughness of at least 4.8 MPa*m 1 / 2 Plane distortion (K IC ) Achieves fracture toughness. In other embodiments, the novel polycrystalline material has a fracture toughness of at least 4.9 MPa*m 1 / 2 Plane distortion (K IC ) Achieves fracture toughness. In further embodiments, the novel polycrystalline material has a fracture toughness of at least 5.0 MPa*m 1 / 2 Plane distortion (K IC ) Achieves fracture toughness. In other embodiments, the novel polycrystalline material has a fracture toughness of at least 5.1 MPa*m 1 / 2 Plane distortion (K IC ) Achieves fracture toughness. In further embodiments, the novel polycrystalline material has a fracture toughness of at least 5.2 MPa*m 1 / 2 Plane distortion (K IC ) Achieves fracture toughness. In other embodiments, the novel polycrystalline material has a fracture toughness of at least 5.3 MPa*m 1 / 2 Plane distortion (K IC ) Achieves fracture toughness. 【0045】 In one embodiment, the novel polycrystalline material achieves an AC dielectric strength (1 mm) of at least 12.0 kV / mm. In another embodiment, the novel polycrystalline material achieves an AC dielectric strength (1 mm) of at least 12.2 kV / mm. In yet another embodiment, the novel polycrystalline material achieves an AC dielectric strength (1 mm) of at least 12.4 kV / mm. In yet another embodiment, the novel polycrystalline material achieves an AC dielectric strength (1 mm) of at least 12.6 kV / mm. In yet another embodiment, the novel polycrystalline material achieves an AC dielectric strength (1 mm) of at least 12.8 kV / mm. In yet another embodiment, the novel polycrystalline material achieves an AC dielectric strength (1 mm) of at least 13.0 kV / mm. In yet another embodiment, the novel polycrystalline material achieves an AC dielectric strength (1 mm) of at least 13.2 kV / mm. In yet another embodiment, the novel polycrystalline material achieves an AC dielectric strength (1 mm) of at least 13.4 kV / mm. In yet another embodiment, the novel polycrystalline material achieves an AC dielectric strength (1 mm) of at least 13.6 kV / mm. In yet another embodiment, the novel polycrystalline material achieves an AC dielectric strength (1 mm) of at least 13.8 kV / mm. In yet another embodiment, the novel polycrystalline material achieves an AC dielectric strength (1 mm) of at least 14.0 kV / mm. In yet another embodiment, the novel polycrystalline material achieves an AC dielectric strength (1 mm) of at least 14.2 kV / mm. In yet another embodiment, the novel polycrystalline material achieves an AC dielectric strength (1 mm) of at least 14.3 kV / mm. In yet another embodiment, the novel polycrystalline material achieves an AC dielectric strength (1 mm) of at least 14.4 kV / mm. In yet another embodiment, the novel polycrystalline material achieves an AC dielectric strength (1 mm) of at least 14.5 kV / mm. In yet another embodiment, the novel polycrystalline material achieves an AC dielectric strength (1 mm) of at least 14.6 kV / mm. In further embodiments, the novel polycrystalline material achieves an AC dielectric strength (1 mm) of at least 14.7 kV / mm. In other embodiments, the novel polycrystalline material achieves an AC dielectric strength (1 mm) of at least 14.8 kV / mm.In yet another embodiment, the novel polycrystalline material achieves an AC dielectric strength (1 mm) of at least 14.9 kV / mm. In yet another embodiment, the novel polycrystalline material achieves an AC dielectric strength (1 mm) of at least 15.0 kV / mm. In yet another embodiment, the novel polycrystalline material achieves an AC dielectric strength (1 mm) of at least 15.1 kV / mm. In yet another embodiment, the novel polycrystalline material achieves an AC dielectric strength (1 mm) of at least 15.2 kV / mm. In yet another embodiment, the novel polycrystalline material achieves an AC dielectric strength (1 mm) of at least 15.3 kV / mm. In yet another embodiment, the novel polycrystalline material achieves an AC dielectric strength (1 mm) of at least 15.4 kV / mm. In yet another embodiment, the novel polycrystalline material achieves an AC dielectric strength (1 mm) of at least 15.5 kV / mm. In yet another embodiment, the novel polycrystalline material achieves an AC dielectric strength (1 mm) of at least 15.6 kV / mm. 【0046】 In one embodiment, the novel polycrystalline material achieves a dielectric constant of at least 12.0 (4 GHz). In another embodiment, the novel polycrystalline material achieves a dielectric constant of at least 12.2 (4 GHz). In yet another embodiment, the novel polycrystalline material achieves a dielectric constant of at least 12.4 (4 GHz). In another embodiment, the novel polycrystalline material achieves a dielectric constant of at least 12.6 (4 GHz). In yet another embodiment, the novel polycrystalline material achieves a dielectric constant of at least 12.8 (4 GHz). In another embodiment, the novel polycrystalline material achieves a dielectric constant of at least 13.0 (4 GHz). In yet another embodiment, the novel polycrystalline material achieves a dielectric constant of at least 13.2 (4 GHz). In another embodiment, the novel polycrystalline material achieves a dielectric constant of at least 13.4 (4 GHz). In yet another embodiment, the novel polycrystalline material achieves a dielectric constant of at least 13.6 (4 GHz). In another embodiment, the novel polycrystalline material achieves a dielectric constant of at least 13.8 (4 GHz). In yet another embodiment, the novel polycrystalline material achieves a dielectric constant of at least 14.0 (4 GHz). In another embodiment, the novel polycrystalline material achieves a dielectric constant of at least 14.2 (4 GHz). In yet another embodiment, the novel polycrystalline material achieves a dielectric constant of at least 14.4 (4 GHz). In another embodiment, the novel polycrystalline material achieves a dielectric constant of at least 14.6 (4 GHz). In yet another embodiment, the novel polycrystalline material achieves a dielectric constant of at least 14.8 (4 GHz). In another embodiment, the novel polycrystalline material achieves a dielectric constant of at least 15.0 (4 GHz). In yet another embodiment, the novel polycrystalline material achieves a dielectric constant of at least 15.1 (4 GHz). In another embodiment, the novel polycrystalline material achieves a dielectric constant of at least 15.2 (4 GHz). In further embodiments, the novel polycrystalline material achieves a dielectric constant of at least 15.3 (4 GHz). In other embodiments, the novel polycrystalline material achieves a dielectric constant of at least 15.4 (4 GHz).In yet another embodiment, the novel polycrystalline material achieves a dielectric constant of at least 15.5 (4 GHz). In yet another embodiment, the novel polycrystalline material achieves a dielectric constant of at least 15.6 (4 GHz). In yet another embodiment, the novel polycrystalline material achieves a dielectric constant of at least 15.7 (4 GHz). 【0047】 In one embodiment, the novel polycrystalline material is 5.0 × 10 -4 The following loss tangent (4 GHz) is achieved. In another embodiment, the novel polycrystalline material is 4.0 × 10 -4 The following loss tangent (4 GHz) is achieved. Furthermore, in another embodiment, the novel polycrystalline material is 3.0 × 10 -4 The following loss tangent (4 GHz) is achieved. In another embodiment, the novel polycrystalline material is 2.0 × 10 -4 The following loss tangent (4 GHz) is achieved. Furthermore, in another embodiment, the novel polycrystalline material is 1.0 × 10 -4 The following loss tangent (4 GHz) is achieved. In another embodiment, the novel polycrystalline material is 9.0 × 10 -5 The following loss tangent (4 GHz) is achieved. Furthermore, in another embodiment, the novel polycrystalline material is 8.0 × 10 -5 The following loss tangent (4 GHz) is achieved. In another embodiment, the novel polycrystalline material is 7.0 × 10 -5 The following loss tangent (4 GHz) is achieved. Furthermore, in another embodiment, the novel polycrystalline material is 6.0 × 10 -5 The following loss tangent (4 GHz) is achieved. In another embodiment, the novel polycrystalline material is 5.0 × 10 -5 The following loss tangent (4 GHz) is achieved. Furthermore, in another embodiment, the novel polycrystalline material is 4.0 × 10 -5 The following loss tangent (4 GHz) is achieved. In another embodiment, the novel polycrystalline material is 3.0 × 10 -5 The following loss tangent (4 GHz) is achieved. Furthermore, in another embodiment, the novel polycrystalline material is 2.0 × 10 -5 The following loss tangent (4GHz) is achieved. 【0048】 In one method, the novel polycrystalline material achieves plasma etching resistance. In one embodiment, the novel polycrystalline material achieves a bulk etching rate of 0.07 micrometers / hour or less when tested according to the etching rate test procedure described in the Material Characterization section of this specification. In another embodiment, the novel polycrystalline material achieves a bulk etching rate of 0.06 micrometers / hour or less. In yet another embodiment, the novel polycrystalline material achieves a bulk etching rate of 0.05 micrometers / hour or less. In yet another embodiment, the novel polycrystalline material achieves a bulk etching rate of 0.04 micrometers / hour or less. In yet another embodiment, the novel polycrystalline material achieves a bulk etching rate of 0.03 micrometers / hour or less. In yet another embodiment, the novel polycrystalline material achieves a bulk etching rate of 0.02 micrometers / hour or less. In yet another embodiment, the novel polycrystalline material achieves a bulk etching rate of 0.01 micrometers / hour or less. 【0049】 As shown in the examples, novel materials can achieve specific colors. In some embodiments, polycrystalline materials achieve white in the sintered state. In some embodiments, polycrystalline materials are translucent in the sintered state. Such color properties can provide improved aesthetics. 【0050】 [v. Form and Use of the Product] Novel polycrystalline materials can take various product forms and can be used in a variety of industrial applications. In one embodiment, the novel polycrystalline material is a bulk (monolithic) polycrystalline material. In one embodiment, the novel polycrystalline material is used in semiconductor processing applications. In one embodiment, the novel polycrystalline material is in the form of a semiconductor component. In one embodiment, the semiconductor component is in the form of a nozzle material or a nozzle. In one embodiment, the semiconductor component is configured for use in a plasma environment. 【0051】 [vi. Material Characterization] As described above, X-ray diffraction (XRD) can be used to determine the amount of crystalline phase in the polycrystalline materials described herein. The XRD apparatus should be a Bruker D8 Discover (Bruker Corp., 40 Manning Rd, Billerica, MA 01821) or an equivalent XRD apparatus. The XRD radiation should be copper Kα rays. The output should be 1.6 kW. The scan range should be 20° to 70° (2θ) (d = 4.5 Å to 1.35 Å). The following table provides primary and secondary peaks of the crystalline phase relevant to the material characterization objectives. [Table A] 【0052】 The following standards should be used to determine the material properties of the polycrystalline materials described herein. • Density should be measured according to ASTM C373-18. • Grain size should be measured according to ASTM E112-13(2021). The modulus of rupture (MOR) should be measured according to C1161-18, where the test rods are manufactured in a "Type B Configuration" with a rod thickness of 4 mm (A) and a rod width of 3 mm (B). The minimum number of rods used for the test is 5. ·Plane strain (K ICFracture strength should be measured using the "notched beam" method, which has a rod thickness of 4 mm (A) and a rod width of 3 mm (B). The minimum number of rods used for the test is 5. The test rods are notched to an intermediate thickness (T / 2) (2 mm deep in this embodiment) using a diamond wafer blade with a notch width of 0.010 ± 0.002 inches. Each sample rod is placed on a 1-inch support span consisting of a ball and rod support system, with the notch centered below a 0.125-inch (1 / 8-inch) loading ball, with the notch facing downwards (away from the loading ball). The rods are loaded until fracture occurs within the Instron test frame. The actual rod thickness and width are measured near the fracture. The solid thickness at the fracture is measured at three locations and averaged. IC The fracture toughness value is calculated for each rod using the load at fracture and geometric data. The average K of at least five test specimens is used. IC Fracture toughness is K in the final report. IC It is used as a fracture toughness value. The dielectric constant and loss tangent should be tested by evaluating the dominant TE01 (transverse electric field) resonant mode. Such evaluation methods are described, for example, in the following NIST (National Institute of Standards and Technology) technical note: ○ Janezic, Michael D., N. Paulter, and J. Blendell. "Dielectric and conductor-loss characterization and measurements on electronic packaging materials," NIST Technical note 1520 (2001) (available at https: / / doi.org / 10.6028 / NIST.TN.1520) The etching rate is measured by lapping the sample with progressively smaller particle sizes of diamond abrasive, then polishing it with a diamond slurry on a Sn composite lapping plate, and finally etching it with carbon tetrafluoride (CF4) for 10 hours. Here, the gas flow rate is set to 5.0 Pa and 50 sccm, and the RF power of the upper and lower plates is set to 135 W (13.56 MHz) and 10 W (13.56 MHz), respectively. As a result, an ion energy of less than 200 eV is expected to be obtained, and if possible, all samples will be etched simultaneously. The etching rate is calculated from the differential step height measurement obtained via diamond stylus profilometry between the plasma-exposed and masked portions of the sample surface. 【0053】 [vii. Others] These and other aspects, advantages, and novel features of this new technology are described in part in this specification and the drawings and can be made apparent to those skilled in the art by examining this specification and the drawings or by practicing one or more embodiments of the technology provided herein. 【0054】 Among these disclosed advantages and improvements, other objectives and advantages of the present invention will become apparent from this specification and the drawings. While detailed embodiments of the present invention are disclosed herein, it should be understood that the disclosed embodiments are merely examples of the present invention, which may be embodied in various forms. Furthermore, each example shown in relation to the various embodiments of the present invention is for illustrative purposes only and is not intended to be limiting. 【0055】 Throughout the specification and claims, unless the context clearly indicates otherwise, the following terms have the meanings expressly associated herein. The expressions “in one embodiment” and “in several embodiments” as used herein do not necessarily refer to the same embodiment, but may be the same. Furthermore, the expressions “in another embodiment” and “in several other embodiments” as used herein do not necessarily refer to different embodiments, but may be different. Therefore, various embodiments of the present invention can be readily combined without departing from the scope or spirit of the invention. 【0056】 Furthermore, as used herein, the term “or” is an inclusive “or” operator and is synonymous with the term “and / or” unless the context clearly indicates otherwise. The term “based on” is not exclusive and may be based on additional elements not described unless the context clearly indicates otherwise. Furthermore, throughout the specification, the meanings of “a,” “an,” and “the” include the plural form unless the context clearly indicates otherwise. Also, the meaning of “in” includes “in” and “on” unless the context clearly indicates otherwise. 【0057】 While some embodiments of the present invention have been described, it should be understood that these embodiments are merely illustrative and not limiting. Furthermore, it will become clear to those skilled in the art that many modifications are possible. Moreover, the various steps can be performed in any order unless the context clearly requires otherwise, and applicable steps can be added and / or removed. [Brief explanation of the drawing] 【0058】 [Figure 1] This figure shows one embodiment of a method for producing a polycrystalline material having controlled amounts of YAP phase and YZ phase. 【0059】 [Figure 2]This figure shows one embodiment of a method for preparing a precursor powder. 【0060】 [Figure 3] This figure shows an embodiment for introducing zirconium into a precursor powder to facilitate the production of a final powder having a YZ phase. 【0061】 [Figure 4] This graph shows the crystalline phase as a function of temperature for various materials in Example 1. [Figure 5] This graph shows the crystalline phase as a function of temperature for various materials in Example 1. [Figure 6] This graph shows the crystalline phase as a function of temperature for various materials in Example 1. 【0062】 [Figure 7] This is a SEM micrograph of the final YAP / YAG product from Example 2. 【0063】 [Figure 8] This is an SEM micrograph of the final YAP / YAG / YZ product from Example 2. 【0064】 [Figure 9] This is a backscatter SEM micrograph of the final YAP / YAG / YZ product from Example 2. 【0065】 [Figure 10a] This is a photograph showing the bulk (monolithic) final component of Example 2. 【0066】 [Figure 10b] This is a photograph showing the white, translucent final component of Example 2, which has a YZ phase. 【0067】 [Figure 11a] This graph shows various properties of the alloy from Example 1. [Figure 11b] This graph shows various properties of the alloy from Example 1. [Figure 11c] This graph shows various properties of the alloy from Example 1. [Figure 11d] This graph shows various properties of the alloy from Example 1. [Figure 11e] This graph shows various properties of the alloy from Example 1. [Figure 11f] This graph shows various properties of the alloy from Example 1. [Modes for carrying out the invention] 【0068】 <Example 1> Formulation and calcination of starting materials 【0069】 High-purity yttria (Y2O3) and alumina (Al2O3) were blended to prepare a series of powders containing 45-50 mol% yttria and 50-55 mol% alumina. The blended powders were calcined at various temperatures for 6 hours. Subsequently, the crystalline phase of the calcined samples was determined as a function of composition and calcination time using X-ray diffraction (XRD) (the material property evaluation method is defined in section vi). The results are shown in Tables 1-3 and Figures 4-6 below. [Table 1] [Table 2] [Table 3] 【0070】 As shown, YAP (YAlO3), YAM (Y4Al2O9), YAG (Y3Al5O 12The adjusted amounts of the yttria and alumina phases can be prepared using predetermined amounts of yttria and alumina and pre-selected calcination conditions. Therefore, materials having pre-selected crystalline phase structures can be produced. For example, as shown in Table 1, to produce a material with a high weight fraction of the YAP phase (e.g., ≥95 wt% YAP), a molar ratio of yttria:alumina of approximately 50:50 can be pre-selected and then calcined at a temperature of 1250°C. As another example, a molar ratio of yttria:alumina of approximately 45:50 can be pre-selected and then calcined at a temperature of 1250°C to produce a bulk material having approximately 60 wt% YAP phase or approximately 38% YAG phase. As the data shows, many other combinations can be pre-selected and achieved. 【0071】 <Example 2> Post-calcination treatment and firing of the starting material 【0072】 Several powders were prepared according to Example 1. These powders were selected to have a high weight fraction of the YAG phase. Some powders (batches 1.1-1.4) were attrition-milled using alumina as the milling medium, and several other powders (batches 2.1-2.6) were attrition-milled using zirconia (ZrO2) as the milling medium. For batch number 2.4, additional zirconia particles (approximately 0.5 wt%) were added during milling to achieve the target zirconium content. The powders were then screened with a 500-mesh sieve, blended with a suitable organic binder, and then spray-dried. The powders were then packed into molds, followed by the formation of solid compacts by dry pressing, and then sintered at approximately 1650°C for 4-6 hours to produce bulk parts. After sintering, various properties of the bulk parts were measured and characterized. The results are shown in Tables 4-5 below (the material characterization method is defined in section vi). Photographs of typical bulk components are shown in Figures 10a to 10b. Various graphs showing the material properties of Example 1 are shown in Figures 11a to 11f. 【0073】 For comparison, bulk components were prepared from conventional pure yttria powder using a generally similar method as described above. This bulk material was white and contained 4.95 g / cm³ of yttria powder. 3 Density, average particle size of 3.0 micrometers, maximum particle size of approximately 15 micrometers, MOR of 130 MPa (4 points, MPa), 1.2 MPaam 1 / 2 K IC Fracture toughness, dielectric constant of 11.5 (4 GHz), and 2.5 × 10⁻⁶ -5 We achieved a loss tangent of (4GHz). [Table 4] [Table 5] 【0074】 [Phase differences between alumina-milled powder and zirconia-milled powder] 【0075】 As shown in Table 4, different phases can be achieved by using alumina or zirconia milling media, or by adding zirconia particles to the powder. Products prepared from alumina milled powder yielded bulk products (1.1-1.4) consisting essentially of YAP and YAG phases. Products prepared from zirconia milled powder had YAP and YAG phases, but also contained a measurable amount of Y4Zr3O 12The bulk products (2.1-2.6) also contained a (YZ) phase. The formation of the YZ phase is a result of zirconium migrated to the formulation during attrition milling. As indicated by batch / part number 2.4, the YZ phase can also be achieved by adding a zirconium-containing material (e.g., zirconia) to the bulk powder. As will be described in more detail below, the addition of zirconium can impart beneficial properties. Zirconium can be introduced to produce the YZ phase, for example, by using a zirconium-containing milling medium and / or by directly adding a zirconium material (e.g., zirconia) to the powder blend. Organic solutions or aqueous solutions containing zirconium can also be used to introduce zirconium. 【0076】 [density] 【0077】 As shown in Table 5, a high density was achieved. Considering that the theoretical densities of the YAP phase and YAG phase are reported to be 5.35 g / cc and 4.55 g / cc, respectively, the measured density values ​​are very high. 【0078】 [Microstructure and particle size] 【0079】 As shown in Table 5, the average particle size is small and reproducible. The maximum particle size is similarly small. 【0080】 Figure 7 is a micrograph of bulk part number 1.4 (79.5% YAP phase and 20.5% YAG phase by weight). As shown, the grain size is uniform and the overall composition is homogeneous. The absence of porosity is noteworthy and supports the measured density being close to the theoretical maximum. The intragranular structure is also non-porous. A small amount of pores are present, but they are intergranular and located along the grain boundaries. Therefore, improvements in mechanical properties and / or corrosion resistance can be achieved. 【0081】 Figure 8 is an SEM micrograph of bulk part number 2.1 (75% YAP phase, 23.5% YAG phase, and 1.5% YZ phase by weight). The YAP / YAG weight ratio is similar to that of bulk part number 1.4 shown in Figure 7, but it has 1.5 wt% YZ phase. Although not bound by theory, the presence of the YZ phase is thought to contribute to the reduction in grain size and improvement in uniformity. At the sintering temperature (e.g., approximately 1650°C), zirconium may be in a solid solution state with yttria. Upon cooling, the YZ phase precipitates at the grain boundaries, thereby reducing some of the yttria from the system and shifting the YAP / YAG ratio slightly closer to YAG. 【0082】 Figure 9 is a backscatter SEM micrograph of bulk part number 2.1 (91% YAP, 8% YAG, and 1% YZ phase by weight), showing the physical properties of the YZ precipitate phase. The dark phase is YAG, the gray phase is YAP, and the small white areas are YZ precipitates. 【0083】 [MOR (Moment of Ratio) and Fracture Toughness] 【0084】 As shown in Table 5, the bulk components achieved a dramatic improvement in mechanical properties compared to the pure YAG phase and the pure yttria phase. The four-point bending strength (MOR) of the yttria phase and the YAG phase is approximately 100-150 MPa, and as can be seen from the comparative data of the bulk yttria products provided above, both materials generally have low fracture toughness, typically around 1.2 MPa*m. 1 / 2 To achieve this. 【0085】 In contrast, the material of the present invention achieves a high MOR (321-386 MPa), which is similar to the MOR (>300 MPa) of high-purity alumina. The material of the present invention also exhibits extremely high fracture toughness (4.5-5.3 MPa*m). 1 / 2 This achieves the following: In fact, bulk part number 2.1 (91% YAP phase, 8% YAG phase, 1% YZ phase by weight) has a four-point bending strength of 386 MPa and 5.3 MPa·m 1 / 2It was measured to have fracture toughness. The improvement of these mechanical properties provides great advantages in the design and use of components and in processes that require diamond grinding / machining. 【0086】 [Dielectric properties] 【0087】 The materials of the present invention exhibit very good dielectric performance. As confirmed by the comparative data of the bulk yttria products provided above, pure yttria has a dielectric constant of about 11.5 and a loss tangent of 2×10 -5 The materials of the present invention achieve a dielectric constant in the range of 14 - 16, and the loss tangent is in the range of 3×10 -5 ~8×10 -5 The dielectric constant of the pure YAP phase has been reported to exceed 15, while the dielectric constant of the pure YAG phase has been reported to be about 11.7. The variation in the dielectric constant shown by the composition of Example 2 is due to the relative contents of the YAG phase and the YAP phase. 【0088】 [Color] 【0089】 Another interesting result was the color of the bulk products made from zirconia - milled powder. As shown in Figure 10a, the products (Materials 1.1 - 1.4) made from alumina - milled powder are tan (light brown). However, surprisingly, the YZ - containing materials (2.1 - 2.6) achieve a bright white color. The YZ - containing materials are also translucent (Figure 10b). Therefore, in addition to the improvement of physical properties, the YZ - containing materials can provide products with improved appearance. 【0090】 <Example 3> Evaluation of Plasma Etch Resistance 【0091】 Additional coupons were prepared from the powder of material 2.1 in Example 2. Comparative coupons were prepared from aluminum oxide (99.5% and 99.8% purity) and yttrium oxide. Samples for plasma etching tests were prepared by lapping with diamond abrasives of progressively smaller particle size and finally polishing with a diamond slurry on a Sn composite lapping plate. After lapping, surface roughness measurements were performed over a 700 × 700 μm area using a Zeiss LSM 800 scanning laser confocal microscope, and the three-dimensional surface texture was calculated according to ISO 25178. The results are shown in Table 6 below. 【0092】 Next, carbon tetrafluoride (CF4) etching was performed for 10 hours. The gas flow rate was set to 5.0 Pa and 50 sccm. The RF power for the upper and lower plates was set to 135 W (13.56 MHz) and 10 W (13.56 MHz), respectively, and the expected ion energy was less than 200 eV. All material samples were etched simultaneously to minimize possible differences in etching conditions. The etching rate was calculated from the difference step height measurement obtained via diamond stylus profilometry between the plasma-exposed and masked portions of the sample. The etching rate results are shown in Table 6 below. [Table 6] 【0093】 As shown, Sample 2.1 of Example 2 achieves lower surface roughness compared to the comparative material. Sample 2.1 of Example 2 also achieves higher density and lower particle size compared to the comparative material. Sample 2.1 also achieves much better plasma etching resistance compared to the comparative alumina material. Sample 2.1 achieves an etching rate comparable to the comparative yttria material, but with much better mechanical properties. 【0094】 While various embodiments of this disclosure have been described in detail, it will be apparent to those skilled in the art that modifications and applications of these embodiments will arise. However, it should be explicitly understood that such modifications and applications will remain within the spirit and scope of this disclosure.

Claims

[Claim 1] (a) at least 50 wt% of a yttrium aluminum perovskite (YAP) phase, (b) at least 0.1% by weight of yttrium zirconate (YZ) phase, A polycrystalline material containing [a certain substance]. [Claim 2] The polycrystalline material according to claim 1, comprising at least 0.2 wt% of YZ phase, or at least 0.3 wt% of YZ phase, or at least 0.4 wt% of YZ phase, or at least 0.5 wt% of YZ phase, or at least 0.6 wt% of YZ phase, or at least 0.7 wt% of YZ phase, or at least 0.8 wt% of YZ phase, or at least 0.9 wt% of YZ phase, or at least 1.0 wt% of YZ phase, or at least 1.2 wt% of YZ phase, or at least 1.4 wt% of YZ phase, or at least 1.6 wt% of YZ phase, or at least 1.8 wt% of YZ phase, or at least 2.0 wt% of YZ phase, or at least 2.2 wt% of YZ phase, or at least 2.4 wt% of YZ phase, or at least 2.6 wt% of YZ phase, or at least 2.8 wt% of YZ phase, or at least 3.0 wt% of YZ phase. [Claim 3] A polycrystalline material according to claim 1 or 2, comprising 10% by weight or less of YZ phase, or 9% by weight or less of YZ phase, or 8% by weight or less of YZ phase, or 7% by weight or less of YZ phase, or 6% by weight or less of YZ phase, or 5% by weight or less of YZ phase, or 4% by weight or less of YZ phase, or 3% by weight or less of YZ phase, or 2% by weight or less of YZ phase, or 1% by weight or less of YZ phase. [Claim 4] A polycrystalline material according to any of the preceding claims, comprising at least 55% by weight of YAP phase, or at least 60% by weight of YAP phase, or at least 65% by weight of YAP phase, or at least 70% by weight of YAP phase, or at least 75% by weight of YAP phase, or at least 80% by weight of YAP phase, or at least 82% by weight of YAP phase, or at least 84% by weight of YAP phase, or at least 86% by weight of YAP phase, or at least 88% by weight of YAP phase, or at least 90% by weight of YAP phase, or at least 92% by weight of YAP phase, or at least 94% by weight of YAP phase, or at least 95% by weight of YAP phase, or at least 96% by weight of YAP phase, or at least 97% by weight of YAP phase, or at least 98% by weight, or at least 99% by weight of YAP phase. [Claim 5] A polycrystalline material according to any of the preceding claims, comprising 0.1 to 49.9% by weight of a yttrium aluminum garnet (YAG) phase. [Claim 6] At least 1% by weight of YAG phase, or at least 2% by weight of YAG phase, or at least 3% by weight of YAG phase, or at least 4% by weight of YAG phase, or at least 5% by weight of YAG phase, or at least 6% by weight of YAG phase, or at least 7% by weight of YAG phase, or at least 8% by weight of YAG phase, or at least 9% by weight of YAG phase, or at least 10% by weight of YAG phase, or at least 11% by weight of YAG phase, or at least 12% by weight of YAG phase, or at least 13% by weight of Y The polycrystalline material according to claim 5, comprising AG phase, or at least 14% by weight of YAG phase, or at least 15% by weight of YAG phase, or at least 16% by weight of YAG phase, or at least 17% by weight of YAG phase, or at least 18% by weight of YAG phase, or at least 19% by weight of YAG phase, or at least 20% by weight of YAG phase, or at least 21% by weight of YAG phase, or at least 22% by weight of YAG phase, or at least 23% by weight of YAG phase, or at least 24% by weight of YAG phase. [Claim 7] YAG phase of 45% by weight or less, or YAG phase of 40% by weight or less, or YAG phase of 38% by weight or less, or YAG phase of 36% by weight or less, or YAG phase of 34% by weight or less, or YAG phase of 32% by weight or less, or YAG phase of 30% by weight or less, or YAG phase of 28% by weight or less, or YAG phase of 26% by weight or less, or YAG phase of 24% by weight or less, or YAG phase of 22% by weight or less, or YAG phase of 20% by weight or less, or YAG phase of 18% by weight or less, or The polycrystalline material according to claim 5 or 6, comprising 16% by weight or less of YAG phase, or 14% by weight or less of YAG phase, or 12% by weight or less of YAG phase, or 10% by weight or less of YAG phase, or 8% by weight or less of YAG phase, or 6% by weight or less of YAG phase, or 5% by weight or less of YAG phase, or 4% by weight or less of YAG phase, or 3% by weight or less of YAG phase, or 2% by weight or less of YAG phase, or 1% by weight or less of YAG phase, or 0.5% by weight or less of YAG phase. [Claim 8] A polycrystalline material according to any of the preceding claims, comprising 10% by weight or less of an yttria phase, or 8% by weight or less of an yttria phase, or 6% by weight or less of an yttria phase, or 5% by weight or less of an yttria phase, or 4% by weight or less of an yttria phase, or 3% by weight or less of an yttria phase, or 2% by weight or less of an yttria phase, or 1% by weight or less of an yttria phase, or 0.5% by weight or less of an yttria phase, or 0.25% by weight or less of an yttria phase, or 0.1% by weight or less of an yttria phase. [Claim 9] A polycrystalline material according to any of the preceding claims, comprising an alumina phase of 10% by weight or less, or an alumina phase of 8% by weight or less, or an alumina phase of 6% by weight or less, or an alumina phase of 5% by weight or less, or an alumina phase of 4% by weight or less, or an alumina phase of 3% by weight or less, or an alumina phase of 2% by weight or less, or an alumina phase of 1% by weight or less, or an alumina phase of 0.5% by weight or less, or an alumina phase of 0.25% by weight or less, or an alumina phase of 0.1% by weight or less. [Claim 10] The polycrystalline material has a density of at least 4.5 g / cm ３ or at least 4.6 g / cm ３ or at least 4.7 g / cm ３ or at least 4.8 g / cm ３ or at least 4.9 g / cm ３ or at least 5.0 g / cm ３ or at least 5.05 g / cm ３ or at least 5.10 g / cm ３ or at least 5.15 g / cm ３ or at least 5.20 g / cm ３ or at least 5.22 g / cm ３ or at least 5.24 g / cm ３ or at least 5.26 g / cm ３ or at least 5.28 g / cm ３ or at least 5.30 g / cm ３ The polycrystalline material according to any one of the preceding claims, achieving such density. [Claim 11] The polycrystalline material is a polycrystalline material according to any of the preceding claims, which achieves an average particle size of 30 micrometers or less, or 28 micrometers or less, or 26 micrometers or less, or 24 micrometers or less, or 22 micrometers or less, or 20 micrometers or less, or 18 micrometers or less, or 16 micrometers or less, or 14 micrometers or less, or 12 micrometers or less, or 10 micrometers or less, or 8 micrometers or less, or 6 micrometers or less, or 5 micrometers or less, or 4 micrometers or less, or 3 micrometers or less, or 2 micrometers or less. [Claim 12] The polycrystalline material is a polycrystalline material according to any of the preceding claims, which achieves a maximum particle size of 80 micrometers or less, or 70 micrometers or less, or 60 micrometers or less, or 50 micrometers or less, or 40 micrometers or less, or 30 micrometers or less, or 25 micrometers or less, or 20 micrometers or less, or 18 micrometers or less, or 16 micrometers or less, or 14 micrometers or less, or 12 micrometers or less, or 10 micrometers or less, or 9 micrometers or less, or 8 micrometers or less, or 7 micrometers or less, or 6 micrometers or less. [Claim 13] The polycrystalline material according to any of the preceding claims, wherein the polycrystalline material achieves an MOR (4-point) strength of at least 200 MPa, or at least 210 MPa, or at least 220 MPa, or at least 230 MPa, or at least 240 MPa, or at least 250 MPa, or at least 260 MPa, or at least 270 MPa, or at least 280 MPa, or at least 290 MPa, or at least 300 MPa, or at least 310 MPa, or at least 320 MPa, or at least 330 MPa, or at least 340 MPa, or at least 350 MPa, or at least 360 MPa, or at least 370 MPa, or at least 380 MPa, or at least 390 MPa. [Claim 14] The aforementioned polycrystalline material has a pressure of at least 2.0 MPa*m １／２ , or at least 2.2 MPa*m １／２ , or at least 2.4 MPa*m １／２ , or at least 2.6 MPa*m １／２ , or at least 2.8 MPa*m １／２ , or at least 3.0 MPa*m １／２ , or at least 3.2 MPa*m １／２ , or at least 3.4 MPa*m １／２ , or at least 3.6 MPa*m １／２ , or at least 3.8 MPa*m １／２ , or at least 4.0 MPa*m １／２ , or at least 4.2 MPa*m １／２ , or at least 4.4 MPa*m １／２ , or at least 4.5 MPa*m １／２ , or at least 4.6 MPa*m １／２ , or at least 4.7 MPa*m １／２ , or at least 4.8 MPa*m １／２ , or at least 4.9 MPa*m １／２ , or at least 5.0 MPa*m １／２ , or at least 5.1 MPa*m １／２ , or at least 5.2 MPa*m １／２ , or at least 5.3 MPa*m １／２ Plane distortion (K ＩＣ A polycrystalline material according to any of the preceding claims, which achieves fracture toughness. [Claim 15] The polycrystalline material has a voltage of at least 12.0 kV / mm, or at least 12.2 kV / mm, or at least 12.4 kV / mm, or at least 12.6 kV / mm, or at least 12.8 kV / mm, or at least 13.0 kV / mm, or at least 13.2 kV / mm, or at least 13.4 kV / mm, or at least 13.6 kV / mm, or at least 13.8 kV / mm, or at least 14.0 kV / mm, or at least 14.2 kV / mm, or at least 14.3 kV / mm, or at least 14.4 kV / mm A polycrystalline material according to any of the preceding claims, which achieves an AC dielectric strength (1 mm) of at least 14.5 kV / mm, or at least 14.6 kV / mm, or at least 14.7 kV / mm, or at least 14.8 kV / mm, or at least 14.9 kV / mm, or at least 15.0 kV / mm, or at least 15.1 kV / mm, or at least 15.2 kV / mm, or at least 15.3 kV / mm, or at least 15.4 kV / mm, or at least 15.5 kV / mm, or at least 15.6 kV / mm. [Claim 16] The polycrystalline material according to any of the preceding claims, which achieves a dielectric constant (4 GHz) of at least 12.0, or at least 12.2, or at least 12.4, or at least 12.6, or at least 12.8, or at least 13.0, or at least 13.2, or at least 13.4, or at least 13.6, or at least 13.8, or at least 14.0, or at least 14.2, or at least 14.4, or at least 14.6, or at least 14.8, or at least 15.0, or at least 15.1, or at least 15.2, or at least 15.3, or at least 15.4, or at least 15.5, or at least 15.6, or at least 15.

7. [Claim 17] The aforementioned polycrystalline material is 5.0 × 10 －４ The following, or 4.0 x 10 －４ The following, or 3.0 x 10 －４ The following, or 2.0 x 10 －４ The following, or 1.0 × 10 －４ The following, or 9.0 x 10 －５ The following, or 8.0 x 10 －５ The following, or 7.0 x 10 －５ The following, or 6.0 x 10 －５ The following, or 5.0 x 10 －５ The following, or 4.0 x 10 －５ The following, or 3.0 x 10 －５ The following, or 2.0 x 10 －５ A polycrystalline material according to any of the preceding claims, which achieves the following loss tangent (4 GHz). [Claim 18] The polycrystalline material is the polycrystalline material according to any of the preceding claims, which achieves a bulk etching rate of 0.07 micrometers / hour or less, or 0.06 micrometers / hour or less, or 0.05 micrometers / hour or less, or 0.04 micrometers / hour or less, or 0.03 micrometers / hour or less, or 0.02 micrometers / hour or less, or 0.01 micrometers / hour or less. [Claim 19] The polycrystalline material is a polycrystalline material according to any of the preceding claims, which achieves a white color in the sintered state. [Claim 20] The polycrystalline material is a polycrystalline material according to any of the preceding claims, wherein the polycrystalline material is translucent in a sintered state. [Claim 21] The polycrystalline material is a polycrystalline material according to any of the preceding claims, wherein the polycrystalline material is in the form of a semiconductor component. [Claim 22] The semiconductor component is a polycrystalline material according to any of the preceding claims, wherein the semiconductor component is in the form of a nozzle blank or a nozzle. [Claim 23] The polycrystalline material according to claim 21 or 22, wherein the semiconductor component is configured for use in a plasma environment. [Claim 24] A method for producing a polycrystalline material according to any one of claims 1 to 23, (a) YAP (YAlO ３ A step of preparing a green body from a first powder containing the ) phase and the YZ (yttrium zirconate) phase, (b) The process includes the step of sintering the green body at a temperature of 1200°C to 1900°C to form the final product, A method wherein the final product comprises the polycrystalline material described in any one of claims 1 to 23. [Claim 25] The process includes preparing a precursor powder before the process of producing the aforementioned green body. The step of preparing the precursor powder is as follows: (i) A step of preparing a powder blend by blending yttria and alumina, wherein the powder blend contains 45 to 50 mol% yttria and 50 to 55 mol% alumina, (ii) A step of heating the powder blend for a temperature and time sufficient to prepare the precursor powder, wherein the precursor powder comprises at least 50% by weight of YAP phase, 10% by weight or less of yttria phase, and 10% by weight or less of alumina phase, A step of preparing a first powder from the aforementioned precursor powder, The method according to claim 24, including the method described in claim 24. [Claim 26] The method according to claim 25, wherein the precursor powder comprises 9% by weight or less of yttria phase, or 8% by weight or less of yttria phase, or 7% by weight or less of yttria phase, or 6% by weight or less of yttria phase, or 5% by weight or less of yttria phase, or 4% by weight or less of yttria phase, or 3% by weight or less of yttria phase, or 2% by weight or less of yttria phase, or 1% by weight or less of yttria phase, or 0.5% by weight or less of yttria phase, or 0.25% by weight or less of yttria phase, or 0.1% by weight or less of yttria phase. [Claim 27] The method according to claim 25 or 26, wherein the precursor powder comprises 9% by weight or less of an alumina phase, or 8% by weight or less of an alumina phase, or 7% by weight or less of an alumina phase, or 6% by weight or less of an alumina phase, or 5% by weight or less of an alumina phase, or 4% by weight or less of an alumina phase, or 3% by weight or less of an alumina phase, or 2% by weight or less of an alumina phase, or 1% by weight or less of an alumina phase, or 0.5% by weight or less of an alumina phase, or 0.25% by weight or less of an alumina phase, or 0.1% by weight or less of an alumina phase. [Claim 28] The method according to any one of claims 25 to 27, wherein the precursor powder comprises at least 55% by weight of YAP phase, or at least 60% by weight of YAP phase, or at least 65% by weight of YAP phase, or at least 70% by weight of YAP phase, or at least 75% by weight of YAP phase, or at least 80% by weight of YAP phase, or at least 82% by weight of YAP phase, or at least 84% by weight of YAP phase, or at least 86% by weight of YAP phase, or at least 88% by weight of YAP phase, or at least 90% by weight of YAP phase, or at least 92% by weight of YAP phase, or at least 94% by weight of YAP phase, or at least 99% by weight of YAP phase. [Claim 29] The aforementioned precursor powder contains 20% by weight or less of YAM phase (Y ４ Al ２ O ９ The method according to any one of claims 25 to 28, comprising ), or 15% by weight or less of YAM phase, or 10% by weight or less of YAM phase, or 9% by weight or less of YAM phase, or 8% by weight or less of YAM phase, or 7% by weight or less of YAM phase, or 6% by weight or less of YAM phase, or 5% by weight or less of YAM phase, or 4% by weight or less of YAM phase, or 3% by weight or less of YAM phase, or 2% by weight or less of YAM phase, or 1% by weight or less of YAM phase. [Claim 30] The aforementioned precursor powder contains 50% by weight or less of YAG phase (Y ３ Al ５ O １２ The method according to any one of claims 25 to 29, comprising ), or 45% by weight or less of YAG phase, or 40% by weight or less of YAG phase, or 35% by weight or less of YAG phase, or 30% by weight or less of YAG phase, or 25% by weight or less of YAG phase, or 20% by weight or less of YAG phase, or 15% by weight or less of YAG phase, or 10% by weight or less of YAG phase, or 5% by weight or less of YAG phase, or 3% by weight or less of YAG phase, or 1% by weight or less of YAG phase. [Claim 31] The precursor powder contains at least 0.5% by weight of YAG (Y ３ Al ５ O １２ The method according to claim 29, comprising the ) phase, or at least 1% by weight of the YAG phase, or both. [Claim 32] The sintering method according to any one of claims 25 to 31, wherein the sintering includes pressureless sintering. [Claim 33] The method according to any one of claims 25 to 32, wherein the step of preparing the first powder from the precursor powder includes introducing zirconium into the precursor powder. [Claim 34] The method according to claim 33, wherein the introduction step includes adding zirconium-containing powder to the precursor powder. [Claim 35] The method according to claim 34, wherein the zirconium-containing powder includes zirconia. [Claim 36] The method according to any one of claims 33 to 35, wherein the introduction step includes transferring zirconium from the transfer material to the precursor powder. [Claim 37] The method according to claim 36, wherein the transfer material is a milling medium containing zirconium. [Claim 38] The method according to claim 37, wherein the moving step includes milling the precursor powder together with the moving material. [Claim 39] The method according to any one of claims 33 to 38, wherein the introduction step includes exposing the precursor powder to a solution containing zirconium ions. [Claim 40] The method according to any one of claims 25 to 39, wherein the step of preparing the first powder from the precursor powder includes one or more of the following: milling the precursor powder, screening the precursor powder, and spray-drying the precursor powder.

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