ZTA ceramic material and preparation method thereof

Abstract

The invention relates to the technical field of ceramic materials, and particularly discloses a ZTA ceramic material and a preparation method thereof. The preparation method comprises the following steps: mixing aluminum oxide, zirconium oxide, a first auxiliary agent and a second auxiliary agent, carrying out wet ball milling, drying and compression molding to obtain a green body, and sintering to obtain the ZTA ceramic material, the first auxiliary agent is an auxiliary agent capable of forming a liquid phase at 1000 DEG C or below to promote particle rearrangement and initial densification, and comprises at least one of alkali metal oxide, alkaline earth metal oxide, boride, silicate or a precursor thereof; the second auxiliary agent is an auxiliary agent capable of inhibiting grain growth and strengthening the grain boundary through solid solution, segregation or formation of a composite grain boundary phase at the temperature of 1500 DEG C or above, and comprises at least one of rare earth oxide and transition metal oxide. According to the method, the technical bottleneck that the sintering efficiency, the microstructure and the mechanical property of the ZTA ceramic are difficult to consider at the same time in the traditional single auxiliary agent or fixed temperature process is broken through by constructing an auxiliary agent function-temperature interval-sintering requirement dynamic cooperation mechanism.

Description

Technical Field

[0001] This invention relates to the field of ceramic materials technology, and in particular to a ZTA ceramic material and its preparation method. Background Technology

[0002] While traditional alumina ceramics possess advantages such as high hardness, strong wear resistance, and economy, their insufficient flexural strength and fracture toughness limit their application in many high-end scenarios. To overcome this performance shortcoming, researchers often use alumina as a matrix and introduce a specific proportion of nano-zirconia particles to prepare zirconia-toughened alumina (ZTA) ceramics. This material, through the synergistic effects of multiple mechanisms such as phase transformation toughening, microcrack toughening, crack deflection, and crack bridging, significantly improves its flexural strength and fracture toughness while inheriting the inherent properties of alumina ceramics, thereby significantly enhancing the reliability of the material during use. Based on this, ZTA ceramics have been widely used in emerging fields such as electronic devices, biomedical implants, and semiconductor manufacturing.

[0003] Although ZTA ceramics have achieved significant improvements in mechanical properties through multi-mechanism synergistic toughening effects, performance optimization in high-end applications still faces a core technological bottleneck: traditional single sintering aid systems or fixed-temperature sintering processes struggle to simultaneously achieve sintering efficiency, microstructure control, and mechanical property enhancement. During sintering, changes in the temperature gradient directly affect atomic diffusion rates, grain growth behavior, and densification processes. The effectiveness of aids (such as lattice defect repair, grain boundary migration control, and liquid phase formation promotion) is highly dependent on matching specific temperature ranges. Single aids can only function within limited temperature ranges and cannot adapt to the dynamic demands of the entire sintering process, ultimately resulting in uneven grain size and high porosity within the material, thus limiting further improvements in flexural strength and fracture toughness. Fixed-temperature processes lack dynamic adaptation to aid functions; either excessively rapid heating leads to an imbalance between aid and temperature, causing abnormal grain growth, or inadequate heat preservation strategies prevent aids from fully exerting their effects, resulting in insufficient densification. Therefore, constructing a dynamic coordination mechanism of "temperature gradient-additive function" to achieve precise matching between different temperature ranges and the corresponding additive effects has become the key to breaking through the performance bottleneck of ZTA ceramics and promoting their development to higher performance levels. It is also a core technical problem that urgently needs to be solved in the current research field of ZTA ceramic materials. Summary of the Invention

[0004] Based on this, the purpose of this invention is to provide a method for preparing ZTA ceramic materials. By precisely matching and controlling the composite sintering aid system with the temperature gradient during the sintering process, a dynamic synergistic mechanism of aid function, temperature range, and sintering requirements is constructed. This breaks through the technical bottleneck of traditional single aid or fixed temperature process, which makes it difficult to take into account the sintering efficiency, microstructure, and mechanical properties of ZTA ceramics. This achieves the simultaneous realization of the densification process and performance optimization of ZTA ceramics.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: This invention provides a method for preparing ZTA ceramic material, comprising the following steps: mixing alumina, zirconium oxide, a first additive, and a second additive, wet ball milling, drying, pressing into shape, and obtaining a green body; sintering the green body to obtain ZTA ceramic material; The first additive is an additive capable of forming a liquid phase at temperatures below 1000°C to promote particle rearrangement and initial densification, including but not limited to at least one of alkali metal oxides, alkaline earth metal oxides, borides, silicates, or their precursors, such as boron oxide (B₂O₃), lithium oxide (Li₂O), magnesium oxide (MgO), calcium oxide (CaO), strontium oxide (SrO), silicon oxide (SiO₂), calcium carbonate (CaCO₃), magnesium sulfate (MgSO₄), zinc borate (ZnB₂O₄), vanadium pentoxide (V₂O₅), tungsten oxide (WO₃), barium oxide (BaO), gallium oxide (Ga₂O₃), and tin oxide (SnO₂). 2) Antimony oxide (Sb2O3), etc. The second additive is an additive that can inhibit grain growth and strengthen grain boundaries at high temperatures (≥1500℃) through solid solution, segregation or formation of composite grain boundary phases. It includes, but is not limited to, at least one of rare earth oxides and transition metal oxides, such as cerium oxide (CeO2), yttrium oxide (Y2O3), manganese dioxide (MnO2), samarium oxide (Sm2O3), terbium oxide (Tb2O3), praseodymium oxide (Pr2O3), dysprosium oxide (Dy2O3), neodymium oxide (Nd2O3), erbium oxide (Er2O3), holmium oxide (Ho2O3), lanthanum oxide (La2O3), gadolinium oxide (Gd2O3), etc.

[0006] As a further improvement to the above-described solution of the present invention, the first auxiliary agent is boron oxide, and the second auxiliary agent is cerium oxide or yttrium oxide.

[0007] As a further improvement to the above-mentioned scheme of the present invention, the mass percentages of the raw materials of the ZTA ceramic material are as follows: alumina 60%-88%, zirconium oxide 10%-40%, first additive 1%-5%, and second additive 1%-5%.

[0008] As a further improvement to the above-mentioned solution of the present invention, the wet ball milling uses zirconia balls as the milling medium and anhydrous ethanol as the milling medium liquid.

[0009] As a further improvement to the above-mentioned solution of the present invention, the wet ball milling speed is 300-500 rpm and the time is 4-24 h.

[0010] As a further improvement to the above-mentioned solution of the present invention, the wet ball milling yields a slurry particle size D90 of 1-5 nm.

[0011] As a further improvement to the above-mentioned solution of the present invention, the pressing molding is performed by cold isostatic pressing.

[0012] As a further improvement to the above-mentioned solution of the present invention, the pressure in the cold isostatic pressing is 200-310 MPa.

[0013] As a further improvement to the above-mentioned scheme of the present invention, the sintering process includes: a low-temperature liquid phase activation stage, which melts the first additive and promotes initial densification; a medium-temperature transition and volatilization stage, which allows the first additive to volatilize in a controlled manner; and a high-temperature solid-phase sintering and grain boundary strengthening stage, which allows the second additive to play a dominant role.

[0014] As a further improvement to the above-mentioned solution of the present invention, the liquid phase activation stage is as follows: the temperature is raised from room temperature to T1 and held at that temperature; then raised to T2 and held at that temperature; wherein, the melting point of the first additive is -300℃≤T1≤the melting point of the first additive is -100℃; the melting point of the first additive is ≤T2≤the melting point of the first additive is +200℃, and T2<1000℃; The transition and volatilization stage: continue heating from T2 to T3 and hold at that temperature, then gradually heat to T4 and hold at that temperature; the volatilization temperature of the first additive is -50℃≤T3<the volatilization temperature of the first additive +50℃; the volatilization temperature of the first additive +100℃≤T4≤the volatilization temperature of the first additive +300℃, and T4<1500℃; The solid-state sintering stage involves heating from T4 to T5 and holding at that temperature; wherein, 1500℃≤T5≤1700℃.

[0015] The precise matching and control mechanism of temperature gradient and additive function in this invention is as follows: 1. Liquid phase activation stage This stage is the sintering start-up stage. The core objective is to achieve initial densification through the liquid phase action of the first additive, while simultaneously laying a uniform distribution foundation for the subsequent function of the second additive. Operationally, preheating should be performed first. The preheating temperature T1 must be strictly controlled below the melting point of the first additive, with a reference range of [first additive melting point - 300℃ - first additive melting point - 100℃]. Hold at this temperature for 30-90 minutes. This process promotes the volatilization of moisture and residual organic matter inside the ZTA ceramic green body, preventing porosity defects during subsequent high-temperature sintering. It also allows the second additive particles to initially disperse evenly within the green body, reducing agglomeration.

[0016] The temperature is then raised to T2, which should be set near the melting point of the first additive, with a reference range of [first additive melting point - first additive melting point + 200℃]. T2 must also be less than 1000℃ (the critical temperature at which the ZTA ceramic matrix begins large-scale sintering), and held for 30-90 minutes. The heating rate must be strictly controlled at 2-10℃ / min to ensure that the first additive is fully melted and evenly spread on the surface of the ZTA ceramic particles, forming a continuous or semi-continuous liquid phase layer. This liquid phase layer fills the tiny pores between the ZTA ceramic particles, reducing particle diffusion resistance; on the other hand, it promotes particle rearrangement through liquid phase dragging, accelerating the initial densification process and increasing the relative density of the ZTA ceramic green body to 75%-85%. Simultaneously, the molten first additive acts as a carrier, driving the second additive particles to distribute evenly on the surface and in the gaps between the ceramic particles, preventing local enrichment or agglomeration of the second additive, and creating conditions for it to play a solid-phase sintering promoting role in subsequent stages. In this stage, the second additive exists in the form of solid particles, and the amount added should match the liquid phase carrying capacity of the first additive to ensure uniform dispersion in the liquid phase of the first additive without sedimentation or agglomeration, thus preparing for lattice diffusion in the subsequent high-temperature stage.

[0017] 2. Transition and Volatilization Stage The core of the transition and volatilization stage is to achieve the orderly volatilization of the first additive and the initial functional activation of the second additive, achieving a seamless transition of additive functions through precise control of the temperature gradient. Continue heating to T3, which is set near the volatilization initiation temperature of the first additive, with a reference range of [volatilization initiation temperature of the first additive ± 100℃]. Then, a stepped heating mode is adopted, holding at 50-100℃ for 20-50 minutes each time, gradually increasing the temperature to T4. T4 must meet two conditions: first, it must be greater than the volatilization initiation temperature of the first additive to ensure orderly volatilization; second, it must be less than the complete sintering temperature of the ZTA ceramic matrix (1500℃), i.e., T4 < 1500℃, with a reference range of [volatilization initiation temperature of the first additive + 100℃ – volatilization initiation temperature of the first additive + 300℃].

[0018] The stepped heating and segmented heat preservation design effectively controls the volatilization rate of the first additive, preventing rapid temperature rise that could lead to its rapid escape and the formation of numerous porosity defects. The content of the first additive decreases linearly with increasing heat preservation time, and the unvolatilized residue remains in the form of nano-sized particles at the ZTA ceramic grain boundaries. Simultaneously, as the temperature rises above T3, the solid-state sintering activity of the second additive is gradually activated—the second additive (such as Y2O3, MgO, SiO2, etc., selected according to ceramic performance requirements) possesses excellent lattice diffusion capabilities, gradually penetrating to the ZrO2 or Al2O3 grain boundaries within this temperature range through surface diffusion and grain boundary diffusion.

[0019] The second additive reacts with the residual first additive at the interface to form a composite grain boundary phase (such as Y₂O₃-ZrO₂ solid solution, MgO-Al₂O₃ spinel phase, etc.). This composite phase inhibits abnormal grain growth through a pinning effect and fills tiny defects at the grain boundaries, initially improving the grain boundary bonding strength. In this stage, the step heating rate and holding time need to be adjusted according to the diffusion activity of the second additive: if the diffusion coefficient of the second additive is low (such as MgO), the holding time for each stage can be appropriately extended to 40-50 min; if the diffusion coefficient is high (such as SiO₂), it can be shortened to 20-30 min to ensure sufficient diffusion and reaction with the residual first additive.

[0020] 3. High-Temperature Densification and Performance Optimization Stage The solid-state sintering stage is crucial for the densification and performance improvement of ZTA ceramics. The core principle is to fully leverage the solid-state sintering-promoting effect of the second additive to simultaneously optimize the ceramic's relative density and overall performance. The temperature is then increased to T5, which must meet three conditions: first, it must be higher than the complete sintering temperature of the ZTA ceramic matrix (1500℃) to ensure sufficient solid-state sintering; second, it must be lower than the high-temperature degradation temperature of the second additive (e.g., the decomposition temperature of Y2O3 is approximately 2400℃, and the phase transformation temperature of SiO2 is approximately 1713℃) to prevent decomposition, phase transformation, and other degradation phenomena of the second additive; and third, it should not be too high (the reference range is 1500-1700℃) to prevent excessive grain growth.

[0021] The holding time is set to 2-6 hours. Constant temperature holding ensures further diffusion and sintering of ZrO2 and Al2O3 grains, ultimately increasing the relative density of the ZTA ceramic to over 95%. During this process, the second additive optimizes the ceramic properties through the following triple action: 1. Solid-state sintering promoting effect: The second additive, as a lattice diffusion medium, can reduce the diffusion activation energy of ZrO2 and Al2O3 grains, accelerate atomic diffusion and grain fusion, eliminate residual porosity between particles, and improve the density of ceramics. 2. Grain boundary strengthening effect: The composite grain boundary phase formed by the second additive and the residual first additive further densifies the grain boundary, inhibiting grain boundary migration through strong pinning effect. At the same time, the composite phase itself has high fracture toughness, which can significantly improve the fracture resistance of grain boundaries and reduce intergranular fracture. 3. Performance regulation function: The second additive can achieve precise regulation of the thermal and electrical properties of ceramics by adjusting the composition and structure of the composite grain boundary phase. For example, adding Y2O3 can improve the tetragonal phase stability of ZrO2 and enhance the fracture toughness and thermal shock resistance of ceramics; adding SiO2 can reduce the softening temperature of the grain boundary glass phase and improve the sintering density and wear resistance of ceramics; adding MgO can further refine the grains and improve the hardness and strength of ceramics.

[0022] In this stage, the specific temperature and holding time of T5 need to be adjusted according to the type of the second additive: if Y2O3 with good high-temperature stability is selected, T5 can be set to 1600-1700℃, and the holding time can be 3-4 hours; if SiO2 or other additives that are prone to phase transformation at high temperatures are selected, T5 should be controlled at 1500-1600℃, and the holding time should be 2-3 hours to ensure that the second additive can fully play its role in a stable state. At the same time, the amount of the second additive added must be strictly controlled within a reasonable range (mass fraction 0.5%-3%): if the amount added is too low, the sintering promotion and performance regulation effects cannot be fully utilized; if the amount added is too high, it will lead to an excessive amount of composite grain boundary phase, which will reduce the strength and high-temperature resistance of the ceramic.

[0023] The present invention also provides a ZTA ceramic material, which is prepared by the preparation method described above.

[0024] Compared with the prior art, the present invention has the following beneficial effects: This invention selects a first additive with low-temperature sintering-promoting and high-temperature controllable functions, and a second additive with high-temperature structural stabilizing and performance controllable functions, to construct a composite sintering aid system. The first additive must have a low melting point and controllable volatility at high temperatures; its core function is to significantly improve sample density through liquid-phase sintering in the early stages of sintering. The second additive must have high lattice matching with the ZTA ceramic matrix (ZrO2, Al2O3) and be able to further improve sample density through solid solution at high temperatures; its core function is to optimize grain growth and grain boundary bonding through solid-phase sintering mechanisms in the later stages of sintering. Additional functions include: inducing defects through mechanisms other than solid solution, promoting atomic migration speed; preventing excessive grain growth by forming a pinning effect at grain boundaries; and stabilizing more tetragonal ZrO2 at room temperature. The combined effect of the first and second additives allows them to enter the main crystalline phase or grain boundaries, playing a role in doping modification, such as controlling electrical conductivity, thermal conductivity, and ZT value.

[0025] The first and second additives of this invention meet the requirements of no harmful chemical reactions and functional succession at high temperatures. That is, the first additive takes the lead in playing a role at low temperatures and its presence does not inhibit the high-temperature activity of the second additive. At high temperatures, the first additive achieves functional transition through volatilization or phase change, providing space for the second additive to fully exert its solid-state sintering and grain boundary strengthening effects, and avoiding sintering defects caused by functional overlap or conflict between the two additives.

[0026] Unlike the traditional static sintering mode with fixed additives and fixed temperature, the method of this invention achieves orderly activation and complementary relay of the functions of the first and second additives at different sintering stages through segmented control of the temperature gradient. This organically connects low-temperature efficient densification with high-temperature performance optimization, and solves the contradiction in traditional sintering where pursuing efficiency easily leads to performance degradation and ensuring performance easily reduces efficiency.

[0027] This invention clarifies the correspondence between the control parameters (heating rate, holding time) and the functions of additives in each temperature range. It allows for the adjustment of temperature gradients and additive ratios according to the specific performance requirements of ZTA ceramics (such as high density, fine grains, and high toughness), thereby achieving precise and replicable process parameters and reducing the risk of performance fluctuations in industrial production.

[0028] This invention utilizes the synergistic effect of liquid-phase densification, solid-phase structural stability, and composite grain boundary strengthening to ultimately prepare ZTA ceramics that possess high density (relative density ≥ 95%), fine-grained structure (grain size ≤ 3µm), and excellent mechanical properties. Compared with traditional ZTA ceramics sintered with a single additive, it improves flexural strength and fracture toughness, meeting the high-performance application requirements of structural ceramics in fields such as wear resistance and high temperature resistance. Attached Figure Description

[0029] Figure 1 This is a SEM image of the ZTA ceramic material prepared in Example 1 of the present invention; Figure 2 This is a SEM image of the ZTA ceramic material obtained in Example 2 of the present invention; Figure 3 This is a SEM image of the ZTA ceramic material obtained in Example 3 of the present invention; Figure 4 This is a SEM image of the ZTA ceramic material obtained in Example 4 of the present invention; Figure 5 This is a SEM image of the ZTA ceramic material obtained in Example 5 of the present invention; Figure 6 This is a SEM image of the ZTA ceramic material obtained in Example 6 of the present invention; Figure 7 This is a SEM image of the ZTA ceramic material prepared in Example 7 of the present invention; Figure 8 This is a SEM image of the ZTA ceramic material obtained in Example 8 of the present invention; Figure 9 This is a SEM image of the ZTA ceramic material prepared in Comparative Example 1 of this invention; Figure 10 This is a SEM image of the ZTA ceramic material prepared in Comparative Example 2 of this invention; Figure 11 Here is a SEM image of the ZTA ceramic material prepared in Comparative Example 3 of this invention; Figure 12 This is a SEM image of the ZTA ceramic material prepared in Comparative Example 4 of this invention; Figure 13 This is a SEM image of the ZTA ceramic material prepared in Comparative Example 5 of this invention. Detailed Implementation

[0030] To facilitate understanding of the present invention, a more comprehensive description will be given below with reference to specific embodiments. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of the present invention.

[0031] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0032] This embodiment provides a ZTA ceramic material, the preparation method of which includes the following steps: mixing alumina, zirconium oxide, a first additive and a second additive, wet ball milling, drying, pressing into shape to obtain a green body; sintering the green body to obtain the ZTA ceramic material.

[0033] The first additive is capable of forming a liquid phase at temperatures below 1000°C to promote particle rearrangement and initial densification. It includes, but is not limited to, at least one of alkali metal oxides, alkaline earth metal oxides, borides, silicates, or their precursors, such as boron oxide, lithium oxide, magnesium oxide, calcium oxide, strontium oxide, silicon oxide, calcium carbonate, magnesium sulfate, zinc borate, vanadium pentoxide, tungsten oxide, barium oxide, gallium oxide, tin oxide, and antimony oxide. For example, boron oxide can be used as the sole first additive, a combination of boron oxide and lithium oxide can be used as the first additive, or gallium oxide can be used as the sole first additive.

[0034] The second additive is an additive capable of inhibiting grain growth and strengthening grain boundaries at high temperatures (≥1500℃) through solid solution, segregation, or the formation of composite grain boundary phases. It includes, but is not limited to, at least one of rare earth oxides and transition metal oxides, such as cerium oxide, yttrium oxide, manganese dioxide, samarium oxide, terbium oxide, praseodymium oxide, dysprosium oxide, neodymium oxide, erbium oxide, holmium oxide, lanthanum oxide, and gadolinium oxide. For example, cerium oxide can be used as a single second additive, a praseodymium oxide + neodymium oxide composite can be used as a first additive, or yttrium oxide or manganese oxide can be used as a single second additive.

[0035] The ZTA ceramic material in this embodiment has the following raw material mass percentages: alumina 60%-88%, zirconium oxide 10%-40%, first additive 1%-5%, and second additive 1%-5%. Wet ball milling uses zirconium oxide balls as the milling medium and anhydrous ethanol as the milling medium liquid; the wet ball milling speed is 300-500 rpm, and the time is 4-24 hours; the particle size D90 of the slurry obtained by wet ball milling is 1-5 nm. Pressing is performed using cold isostatic pressing, with a pressure of 200-310 MPa.

[0036] In this embodiment, sintering is carried out in air, first by raising the temperature from room temperature to T1 and holding it; then raising it to T2 and holding it; continuing to raise the temperature to T3 and holding it; raising the temperature in stages to T4 and holding it; and finally raising the temperature to T5 and holding it. Specifically, the melting point of the first additive is -300℃≤T1≤first additive melting point-100℃; the melting point of the first additive is ≤T2≤first additive melting point+200℃, and T2<1000℃; the volatilization temperature of the first additive is -50℃≤T3<first additive volatilization temperature+50℃; the volatilization temperature of the first additive+100℃≤T4≤first additive volatilization temperature+300℃, and T4<1500℃; 1500℃≤T5≤1700℃.

[0037] When boron oxide is used as the first additive and cerium oxide or yttrium oxide as the second additive, the sintering conditions are as follows: In air, the temperature is increased from room temperature to 350-400℃ at a rate of 2-3℃ / min and held for 30-60 min; then increased to 500-600℃ at a rate of 2-5℃ / min and held for 30-60 min; then increased in stages by 50℃ and held until 1100-1200℃ is reached; finally, the temperature is increased to 1550-1650℃ at a rate of 2-3℃ / min and held for 2-8 h. The sintering mechanism based on the synergistic effect of temperature and additives in this embodiment is as follows: (1) Low-temperature liquid phase activation stage (room temperature → 500-600℃) Heat from room temperature to 350-400℃ at a rate of 2-3℃ / min (hold for 30-60min): preheating removes impurities and avoids uneven distribution of additives due to sudden temperature rise; The temperature is increased to 500-600℃ at a rate of 2-5℃ / min (and held for 30-60min): 500-600℃ is higher than the melting point of boron oxide (450℃) to ensure the formation of a continuous liquid phase; at the same time, it is lower than the large-scale sintering temperature of ZTA (1000℃) to avoid premature sintering of the matrix. The heating rate matches the requirement of "slow heating to ensure uniform spreading of the additives". The holding time of 30-60min allows boron oxide to fully wet the surface of ZTA particles, fill the micropores, and increase the relative density of the green body to 75%-85%, laying the foundation for subsequent sintering.

[0038] (2) High temperature transition and volatilization stage (500-600℃→1100-1200℃) The temperature was increased in 50°C increments: 600°C → 650°C (hold for 40 min) → 700°C (hold for 40 min) → … → 1100-1200°C (hold for 60 min), with each increment followed by a 50°C hold, and the total heating rate controlled at 3-4°C / min. This stepped heating prevents rapid escape of boron oxide due to sudden temperature increases, which could lead to porosity. Holding at 1100-1200°C, where the boron oxide vapor pressure is approximately 3 mmHg, allows for "linear volatilization," leaving residual additives as nanoparticles at the grain boundaries. Simultaneously, holding at 1100-1200°C activates the solid-state sintering activity of cerium oxide / yttrium oxide. 4+ / Y 3+ Start replacing Zr 4+ It forms a solid solution.

[0039] (3) High-temperature solid-state sintering densification and performance optimization stage (1100-1200℃→1550-1650℃) The temperature is increased from 1100-1200℃ to 1550-1650℃ at a rate of 2-3℃ / min (held for 2-8 hours): 1550-1650℃ is higher than the complete sintering temperature of ZTA (1500℃), ensuring sufficient solid-phase sintering; at the same time, it is lower than the degradation temperature of cerium oxide / yttrium oxide, ensuring its structural stability. Natural cooling is then performed by closing the furnace door to prevent sudden temperature drops that could lead to internal stress cracking. The upper temperature limit of 1650℃ is lower than the melting point of cerium oxide / yttrium oxide, allowing Ce... 4+ / Y 3+ It diffuses fully into the grain boundaries, forming a composite grain boundary phase with residual boron oxide, and controls the grain size to 1-3 μm through a pinning effect. A holding time of 2-8 hours can ultimately increase the relative density of ZTA to over 98%.

[0040] In the early stage of sintering in this invention, due to the low melting point of B2O3 (450℃), it melts first to form a continuous liquid phase medium when the sintering temperature rises to 500-800℃, promoting the sintering of the material through a dissolution-mass transfer mechanism. In the later stage of sintering, as the sintering temperature rises above 1000℃, the B2O3-based liquid phase is gradually consumed and dissipated through volatilization or the formation of a solid solution with the matrix, and the dominant sintering mechanism changes from liquid phase mass transfer to solid phase diffusion. During this stage, the high melting point of CeO2 or Y2O3 becomes prominent, and its unreacted portions are distributed in an isolated form between the grains, becoming structural support points for solid-phase sintering. 4+ / Y 3+ Zr in the ZrO2 lattice 4+ Having similar atomic radii and the same valence, they readily form substitutional solid solutions, Ce 4+ / Y 3+ Replacement of Zr in ZrO2 lattice 4+ This leads to lattice distortion, and in addition, Ce in cerium oxide... 4+It is easily reduced to Ce in a high-temperature reducing atmosphere or when it reacts with certain elements in the matrix. 3+ Due to Ce 3+ With Ce 4+ The different ionic radii of the atoms cause this valence state change to disrupt the electroneutrality and structural integrity of the crystal lattice, resulting in a large number of oxygen vacancies in the lattice. This also leads to lattice distortion, increased defects, and a reduction in the activation energy required for atomic diffusion, which is beneficial for diffusion mass transfer and promotes sintering. 3+ / Y 3+ Ionic radius and Zr 4+ It is close to the ZrO2 crystal lattice and can dissolve into it. This solid solution effect suppresses phase transitions through lattice distortion on the one hand, and Ce on the other hand... 3+ The presence of cerium oxide reduces the phase transition free energy, thereby stabilizing more tetragonal ZrO2 at room temperature and ensuring the toughening effect. Furthermore, cerium oxide / yttrium oxide segregates at grain boundaries during sintering. This segregation pins grain boundary migration, hindering excessive growth of Al2O3 and ZrO2 grains and refining the grain structure. This refined grain structure helps improve the strength and toughness of ZTA ceramics. In addition, cerium oxide / yttrium oxide also regulates the thermal conductivity, electrical conductivity, and dielectric properties of the material. As the second additive in ZTA ceramic preparation, yttrium oxide and cerium oxide share the same function: both can form a solid solution with ZrO2 to induce lattice distortion, segregate at grain boundaries to inhibit excessive grain growth, and stabilize tetragonal ZrO2 at room temperature to promote material densification and improve mechanical properties. The difference lies in the presence of Ce2O3 / yttrium oxide. 3+ / Ce 4+ The dynamic transformation characteristic of dual valence states can generate a large number of additional oxygen vacancies to enhance mass transfer and microcrack toughening, resulting in better improvement in fracture toughness. However, it is sensitive to the sintering atmosphere. Yttrium oxide only stabilizes Y. 3+ With a fixed valence state, a fixed number of defects, and higher stability in solid solutions, the material exhibits superior high-temperature structural and strength stability and strong process adaptability.

[0041] Example 1 This embodiment proposes a ZTA ceramic material, which is prepared from the following powder raw material components by mass fraction: 76% aluminum oxide (Al2O3), 19% zirconium oxide (ZrO2), 3% boron oxide (B2O3), and 2% cerium oxide (CeO2), wherein B2O3 and CeO2 are sintering aids.

[0042] The ZTA ceramic material preparation method in this embodiment includes the following steps: S1. Mix alumina, zirconium oxide, boron oxide and cerium oxide in proportion to obtain a mixed powder. Pour the mixed powder into a cylindrical ball mill jar, add zirconium oxide balls with a diameter of Φ=3mm and anhydrous ethanol, and place it in a planetary ball mill and ball mill at 400 rpm for 8 hours until the particle size D90 is 1.7nm.

[0043] S2. Remove the slurry and filter it. Then put it into a drying oven and dry it at 60℃ for 10 hours. Then press it into shape using a cold isostatic press. The cold isostatic press increases the pressure to 300MPa at a rate of 3MPa / min and holds it for 90s. Then it decreases to normal pressure at a rate of 5MPa / min to obtain the green embryo.

[0044] S3. Place the green body into a square ceramic crucible, then place it into a box furnace. In air, raise the temperature from room temperature to 400℃ at a rate of 2.5℃ / min and hold for 30 min. Then raise the temperature to 600℃ at a rate of 4.5℃ / min and hold for 60 min. Then raise the temperature in 50℃ increments: 600℃ → 650℃ (hold for 40 min) → 700℃ (hold for 40 min) → … → 1100℃ (hold for 60 min). Then raise the temperature from 1100℃ to 1600℃ at a rate of 2.4℃ / min and hold for 4 h. Then let it cool naturally to room temperature and remove it to obtain ZTA ceramic material.

[0045] Example 2 The difference between this embodiment and Embodiment 1 is that the ZTA ceramic material in this embodiment is prepared from the following powder raw material components by mass fraction: 60% alumina, 35% zirconium oxide, 3% boron oxide, and 2% cerium oxide. In the preparation of the ZTA ceramic material in this embodiment, the sintering in step S3 is carried out in air at a rate of 2.5℃ / min from room temperature to 150℃ and held for 30 min, then at a rate of 4.5℃ / min to 400℃ and held for 60 min, then at a rate of 4℃ / min to 1200℃ and held for 30 min, and then at a rate of 2.4℃ / min to 1500℃ and held for 8 h.

[0046] Example 3 The difference between this embodiment and Embodiment 1 is that the ZTA ceramic material in this embodiment is prepared from the following powder raw material components by mass fraction: 85% alumina, 10% zirconium oxide, 3% boron oxide, and 2% cerium oxide. In the preparation of the ZTA ceramic material in this embodiment, the sintering in step S3 is carried out in air at a rate of 2.5℃ / min from room temperature to 50℃ and held for 60 min, then at a rate of 4.5℃ / min to 600℃ and held for 40 min, then at a rate of 4℃ / min to 1000℃ and held for 40 min, and then at a rate of 2.4℃ / min to 1650℃ and held for 6 h.

[0047] Example 4 The difference between this embodiment and Embodiment 1 is that the ZTA ceramic material in this embodiment is prepared from the following powder raw material components by mass fraction: 80% alumina, 10% zirconium oxide, 5% boron oxide, and 5% cerium oxide.

[0048] Example 5 The difference between this embodiment and Embodiment 1 is that the ZTA ceramic material in this embodiment is prepared from the following powder raw material components by mass fraction: 76% alumina, 19% zirconium oxide, 3% boron oxide, and 2% yttrium oxide.

[0049] Example 6 The difference between this embodiment and Embodiment 1 is that the ZTA ceramic material in this embodiment is prepared from the following powder raw material components by mass fraction: 60% alumina, 35% zirconium oxide, 3% boron oxide, and 2% yttrium oxide.

[0050] Example 7 The difference between this embodiment and Embodiment 1 is that the ZTA ceramic material in this embodiment is prepared from the following powder raw material components by mass fraction: 85% alumina, 10% zirconium oxide, 3% boron oxide, and 2% yttrium oxide.

[0051] Example 8 The difference between this embodiment and Embodiment 1 is that the ZTA ceramic material in this embodiment is prepared from the following powder raw material components by mass fraction: 80% alumina, 10% zirconium oxide, 5% boron oxide, and 5% yttrium oxide.

[0052] Comparative Example 1 The difference between this comparative example and Example 1 is that the ZTA ceramic material in this comparative example is prepared from the following powder raw material components by mass fraction: 80% alumina and 20% zirconium oxide.

[0053] Comparative Example 2 The difference between this comparative example and Example 1 is that the ZTA ceramic material in this comparative example is prepared from the following powder raw material components by mass fraction: 76% alumina, 19% zirconium oxide, and 5% boron oxide.

[0054] Comparative Example 3 The difference between this comparative example and Example 1 is that the ZTA ceramic material in this comparative example is prepared from the following powder raw material components by mass fraction: 76% alumina, 19% zirconium oxide, and 5% cerium oxide.

[0055] Comparative Example 4 The difference between this comparative example and Example 1 is that the ZTA ceramic material in this comparative example is prepared from the following powder raw material components by mass fraction: 76% alumina, 19% zirconium oxide, and 5% yttrium oxide.

[0056] Comparative Example 5 The difference between this comparative example and Example 1 is that, in the preparation of the ZTA ceramic material in this comparative example, the sintering in step S3 is carried out in air at a rate of 2-5℃ / min from room temperature to 1500℃ and held for 1-8 hours.

[0057] Test case (1) The ZTA ceramic materials prepared in Examples 1-8 and Comparative Examples 1-5 were characterized to obtain the following results: Figures 1-13 The SEM image shown.

[0058] Figure 1-4 These are SEM images of the product with added B2O3 and CeO2 composite additives. Figure 5-8 This is a SEM image of the composite additives B2O3 and Y2O3. Figure 1-8 The morphology shows that the ceramic matrix has a uniform and dense polycrystalline structure with no obvious agglomeration or macroscopic defects. The grains are tightly bonded and the porosity is low. The zirconium phase and the alumina matrix are well bonded at the interface with no obvious phase separation or pores, which reflects the promoting effect of the additives on sintering densification. The two grain phases are distributed in a coordinated manner. The larger granular α-alumina main crystal phase (about 1-5µm) constitutes the matrix framework, while the smaller zirconium toughening phase (about 0.5-2µm) is uniformly dispersed at the alumina grain boundaries.

[0059] Figure 9 For the SEM morphology of pure ZTA in Comparative Example 1, from Figure 13 It can be seen that the material exhibits a dispersed particle stacking structure, with no effective sintering necks formed between most particles, poor interfacial bonding, and most particles lacking bonding characteristics. Furthermore, there are a large number of interconnected pores and gaps with uneven pore size distribution, resulting in a loose overall structure and the failure to form a dense ceramic sintered body.

[0060] Figure 10 and Figure 12 The following are SEM images of ZTA with only B2O3, CeO2, and Y2O3 added: Compared with pure ZTA, sintering contact appears between particles, but the particle interface bonding is not sufficient, and there are still some irregular closed pores and open pores. A small number of particles are still discretely distributed, and the degree of sintering densification has been improved to some extent.

[0061] Figure 13 For Comparative Example 5, a conventional sintering temperature was used, resulting in better interparticle contact and a more complete sintering neck. However, some pores and voids still existed, and its sintering degree was still somewhat different from that of Example 1.

[0062] The densification effect of ZTA ceramics prepared in Comparative Examples 1-5 was inferior to that of the sample in Example 1, which simultaneously added boron oxide and cerium oxide or yttrium oxide and adopted a heating system with synergistic effect with the additives.

[0063] (2) The ZTA ceramic materials prepared in Examples 1-8 and Comparative Examples 1-5 were subjected to performance tests, and the results are shown in the table below: Density: Grind the surface of the sample to be tested until there are no cutting marks, place it in anhydrous ethanol for ultrasonic cleaning for 5-10 minutes, take it out and put it in an oven to dry at 70°C for 30 minutes, weigh it on a hydrometer balance, and record the reading as m1 after the balance reading stabilizes; (2) Take out the sample, immerse the sample in deionized water for 30 minutes, take it out and transfer it to the tray of the hydrometer containing deionized water, and record the mass m2 when the sample is completely immersed in deionized water after stabilization; (3) Take the sample out of the deionized water, quickly wipe the deionized water off the sample surface and weigh its mass m3. Use the Archimedes method and the immersion medium method to measure the density and density of the material. The calculation formula is as follows: ρ=m1m3 In the formula m2ρ0, ρ is the material density, with units of g / cm³. 3 m1, m2, and m3 represent the mass of the sample in air after drying, the mass of the sample submerged in the medium after immersion, and the mass in air after wiping the liquid off the sample surface, respectively; ρ0 is the density of deionized water, which is 0.997 g / cm³. 3 ; Grain size: The microstructure of the sample surface was characterized using scanning electron microscopy (SEM). Representative fields of view were selected to acquire SEM images (magnification of 7000-8000x). Using the built-in length scale in the image as a reference, at least 20 independent grains without obvious defects were selected in the image, and the equivalent diameter of each grain was measured (for irregularly shaped grains, the arithmetic mean of its longest and shortest axes was taken). The actual grain size was calculated by combining the magnification of the SEM image, and the statistical range of all measured values ​​was taken as the grain size distribution range of the sample.

[0064]

[0065] According to the results in the table above: 1. Density: The ZTA ceramic materials prepared in Examples 1-8 all had densities between 96.5% and 99.0%, indicating extremely high overall densification. Example 1 had the highest density, reaching 99.0%. In contrast, Comparative Example 1 (without any additives) had a density of only 71.0%, significantly lower than all examples. Comparative Examples 2-4 (densities 90.0%-93.5%) with only a single additive and Comparative Example 5 (density 96.0%) using a conventional sintering temperature process also had densities lower than the example samples. This fully demonstrates that the boron oxide and cerium oxide / yttrium oxide composite additive system used in this invention, combined with a precisely controlled temperature gradient sintering process, can effectively promote the densification process of ZTA ceramics and significantly reduce the internal porosity of the material.

[0066] 2. Grain size: The ZTA ceramic materials in Examples 1-8 exhibited grain size distribution ranging from 0.48µm to 2.40µm, with uniform and generally small grain sizes and no obvious abnormal growth. Comparative Example 1 (without additives) showed a wider grain size distribution range (1.00µm-5.10µm), with the maximum grain size significantly exceeding that of the examples. While the grain size distributions of Comparative Examples 2-4 (single additives) and Comparative Example 5 (conventional sintering) were better than those of Comparative Example 1, the upper limit of grain size for some samples was still greater than that of the examples (e.g., the upper limit of grain size in Comparative Example 5 was 2.80µm). This indicates that the synergistic regulation mechanism of the composite additives and temperature gradients in this invention can effectively suppress excessive grain growth, achieving precise control of grain size and laying a structural foundation for optimizing the mechanical properties of the material.

[0067] 3. As can be seen from the comprehensive comparison, the present invention solves the problem of insufficient densification of materials in traditional additive-free or single additive systems by dynamically and synergistically controlling composite sintering aids and temperature gradients, and overcomes the defect of abnormal grain growth in conventional sintering processes. Ultimately, it achieves simultaneous optimization of the densification degree and grain structure regularity of ZTA ceramic materials, providing a key guarantee for the improvement of their mechanical properties.

[0068] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0069] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for preparing ZTA ceramic material, characterized in that, It includes the following steps: Alumina, zirconium oxide, a first additive, and a second additive are mixed, wet-milled, dried, and pressed into a green body to obtain a green body. The green body is then sintered to obtain ZTA ceramic material. The first additive is an additive capable of forming a liquid phase at temperatures below 1000°C for liquid-phase sintering, and is at least one of alkali metal oxides, alkaline earth metal oxides, borides, silicates, or their precursors. The second additive is an additive capable of solid-phase sintering at temperatures above 1500°C, and is at least one of rare earth oxides and transition metal oxides.

2. The method for preparing ZTA ceramic material according to claim 1, characterized in that, The raw materials of the ZTA ceramic material have the following mass percentages: alumina 60%-88%, zirconium oxide 10%-40%, first additive 1%-5%, and second additive 1%-5%.

3. The method for preparing ZTA ceramic material according to claim 1, characterized in that, The first additive is at least one of boron oxide, lithium oxide, magnesium oxide, calcium oxide, strontium oxide, silicon oxide, calcium carbonate, magnesium sulfate, zinc borate, vanadium pentoxide, tungsten oxide, barium oxide, gallium oxide, tin oxide, and antimony oxide; the second additive is at least one of cerium oxide, yttrium oxide, manganese dioxide, samarium oxide, terbium oxide, praseodymium oxide, dysprosium oxide, neodymium oxide, erbium oxide, holmium oxide, lanthanum oxide, and gadolinium oxide.

4. The method for preparing ZTA ceramic material according to claim 1, characterized in that, The wet ball milling process uses zirconia balls as the milling medium and anhydrous ethanol as the milling medium liquid.

5. The method for preparing ZTA ceramic material according to claim 1, characterized in that, The wet ball milling speed is 300-500 rpm and the time is 4-24 h.

6. The method for preparing ZTA ceramic material according to claim 1, characterized in that, The wet ball milling process yields a slurry particle size D90 of 1-5 nm.

7. The method for preparing ZTA ceramic material according to claim 1, characterized in that, The pressing is performed using cold isostatic pressing, where the pressure is 200-310 MPa.

8. The method for preparing ZTA ceramic material according to claim 1, characterized in that, The sintering process includes a liquid phase activation stage, a transition and volatilization stage, and a solid phase sintering stage.

9. The method for preparing ZTA ceramic material according to claim 8, characterized in that, The liquid phase activation stage is as follows: the temperature is raised from room temperature to T1 and held; then raised to T2 and held; wherein, the melting point of the first additive is -300℃≤T1≤the melting point of the first additive is -100℃; the melting point of the first additive is ≤T2≤the melting point of the first additive is +200℃, and T2<1000℃; The transition and volatilization stage: continue heating from T2 to T3 and hold at that temperature, then gradually heat to T4 and hold at that temperature; the volatilization temperature of the first additive is -50℃≤T3<the volatilization temperature of the first additive +50℃; the volatilization temperature of the first additive +100℃≤T4≤the volatilization temperature of the first additive +300℃, and T4<1500℃; The solid-state sintering stage involves heating from T4 to T5 and holding at that temperature; wherein, 1500℃≤T5≤1700℃.

10. A ZTA ceramic material, characterized in that, It is prepared by the preparation method described in any one of claims 1-9.

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