Method for preparing high-density PZTO target material through low-cost normal-pressure sintering

Abstract

The invention relates to the technical field of target materials, and provides a method for preparing a high-density PZTO target material through low-cost normal-pressure sintering, industrial-grade raw materials are adopted, and the cost is reduced by 50% compared with 99.99% of the raw materials; transition metal oxide Mn3O4 is doped, abnormal growth of crystal grains is inhibited, the mechanical strength is improved, and the hardness is larger than or equal to 8 GPa; water-based tape casting is adopted for forming, and pollution of methylbenzene and ethyl alcohol in a traditional process is avoided; sintering aids Bi2O3 and CuO are added in the sintering process to form liquid-phase sintering, and the sintering temperature is reduced to 1200 DEG C; three-stage sintering is adopted, a binder is removed in the first stage of sintering, preliminary densification is conducted in the second stage of sintering, and complete densification is conducted in the third stage of sintering; and the sintering waste is subjected to ball milling and crushing until the particle size is less than or equal to 1 mu m, and then is doped into new powder according to the proportion of 10%-20%, so that the raw material utilization rate is increased to 90%.

Description

Technical Field

[0001] The present invention relates to the technical field of target materials, and particularly to a method for preparing a highly dense PZTO target by low-cost atmospheric pressure sintering. Background Art

[0002] Lead zirconate titanate target is an important sputtering target, abbreviated as PZTO target, which is widely used in the fields of electronic component manufacturing, thermal imagers and nuclear war protection equipment. The current PZTO target process has high costs: traditional PZTO targets rely on hot pressing sintering (HP) or spark plasma sintering (SPS), which require high-pressure equipment > 30 MPa, with large equipment investment and high energy consumption. The raw material purity requirements are stringent: high-purity PbO, ZrO2, and TiO2 with a purity of more than 99.99% are required, and the raw material cost accounts for more than 60%. Performance defects: the density of the atmospheric pressure sintered target is low < 90%, the grain size is large > 5 μm, resulting in easy cracking of the sputtered thin film, poor electrical properties, and a remanent polarization intensity Pr < 20 μC / cm 2 . Therefore, a method for preparing a highly dense PZTO target by low-cost atmospheric pressure sintering is needed. Summary of the Invention

[0003] In view of this, the purpose of the present invention is to propose a method for preparing a highly dense PZTO target by low-cost atmospheric pressure sintering, which solves the problems in the background art.

[0004] Based on the above purpose, the present invention provides a method for preparing a highly dense PZTO target by low-cost atmospheric pressure sintering, including the following steps:

[0005] Step 1, select industrial-grade raw materials: PbO, ZrO2, TiO2 with a purity ≥ 99.5%, and dopants: 0.5 - 2 wt.% of transition metal oxides and 0.1 - 0.5 wt.% of rare earth oxides;

[0006] Step 2, ball mill the above raw materials and dopants for 24 h, and then mix them together after ball milling;

[0007] Step 3, tape cast the mixed materials;

[0008] Step 4, perform atmospheric pressure sintering on the ball-milled raw materials and dopants to obtain the target. The sintering includes three stages:

[0009] The first stage: heat from room temperature to 500 °C at a rate of 2 °C / min and hold for 1 h;

[0010] The second stage: heat from 500 °C to 1000 °C at a rate of 5 °C / min and hold for 2 h;

[0011] The third stage: heat from 1000 °C to 2000 °C at a rate of 3 °C / min and hold for 4 h.

[0012] Preferably, the molar ratio of PbO:ZrO2:TiO2 is 52:28:20.

[0013] Preferably, the transition metal oxide is Mn3O4 and the rare earth oxide is La2O3.

[0014] Preferably, in the second step of ball milling, alcohol is used as the medium and the ball-to-material ratio is 5:1.

[0015] Preferably, the tape casting is water-based tape casting: using water as the solvent and polyvinyl alcohol as the binder.

[0016] Preferably, after the tape casting in the third step, cold isostatic pressing is carried out, and the pressure is 200 MPa.

[0017] Preferably, the particle size of the sintering waste after being ball milled and pulverized in the fourth step is ≤1 μm, and it is backfilled into the new powder at a ratio of 10%-20%.

[0018] Preferably, sintering aids are added in the fourth step of sintering: 0.3-0.8 wt.% of Bi2O3 and 0.2-0.5 wt.% of CuO to form liquid-phase sintering.

[0019] The beneficial effects of the present invention: The present invention provides a method for preparing a low-cost and high-performance PZTO (Pb(Zr,Ti)O3) target by combining an atmospheric pressure sintering process with material modification and green preparation technology, which is applicable to the sputtering coating process in the fields of ferroelectric thin films, piezoelectric devices, memories, etc. Industrial-grade raw materials are used, and the cost is reduced by 50% compared with 99.99% raw materials; doping with transition metal oxide Mn3O4 inhibits abnormal grain growth and improves mechanical strength, with a hardness ≥8 GPa; water-based tape casting is used for forming: using water as the solvent and polyvinyl alcohol (PVA) as the binder to avoid pollution by toluene and ethanol in the traditional process; sintering aids Bi2O3 and CuO are added during the sintering process to form liquid-phase sintering, reducing the sintering temperature to 1200 °C; three-stage sintering is used for sintering, the first stage of sintering removes the binder, the second stage of sintering achieves preliminary densification, and the third stage of sintering achieves complete densification; and the sintering waste is ball milled and pulverized to a particle size ≤1 μm and then backfilled into the new powder at a ratio of 10%-20%, and the raw material utilization rate is increased to 90%. By optimizing the atmospheric pressure sintering process, co-doping of transition metals / rare earths, and gradient structure design, the problems of high cost, low density, and poor film performance in the traditional process are solved. Detailed implementation manners

[0020] To make the purpose, technical solutions and advantages of the present invention clearer, the following further elaborates on the present invention in conjunction with specific embodiments.

[0021] It should be noted that, unless otherwise defined, the technical terms or scientific terms used in the present invention should have the ordinary meanings understood by those with ordinary skills in the field to which the present invention belongs. The "first", "second" and similar terms used in the present invention do not indicate any order, quantity or importance, but are only used to distinguish different components. Words such as "including" or "comprising" mean that the elements or objects appearing before this word cover the elements or objects listed after this word and their equivalents, without excluding other elements or objects. Words such as "connected" or "coupled" are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "Up", "down", "left", "right", etc. are only used to indicate relative positional relationships, and when the absolute position of the object being described changes, the relative positional relationship may also change accordingly.

[0022] Embodiment

[0023] This embodiment provides a method for preparing a highly dense PZTO target by low-cost atmospheric pressure sintering, including the following steps:

[0024] S1, Select industrial-grade raw materials: PbO, ZrO2, TiO2 with a purity ≥ 99.5%, and the molar ratio of PbO:ZrO2:TiO2 is 52:28:20; and dopants: 1.5 wt.% of Mn3O4 and 0.3 wt.% of La2O3;

[0025] S2, Ball-mill the above raw materials and dopants, use alcohol as the medium, the ball-to-material ratio is 5:1, the time is 24 h, and mix them together after ball-milling;

[0026] S3, Cast the mixed materials into a film, use water as the solvent and polyvinyl alcohol as the binder; then perform cold isostatic pressing with a pressure of 200 MPa;

[0027] S4, Sinter the ball-milled raw materials and dopants under atmospheric pressure to obtain the target, and add sintering aids during the sintering process: 0.5 wt.% of Bi2O3 and 0.3 wt.% of CuO to form liquid-phase sintering;

[0028] The sintering includes three stages:

[0029] The first stage: Heat from room temperature to 500 °C at a rate of 2 °C / min and hold for 1 h;

[0030] The second stage: Heat from 500 °C to 1000 °C at a rate of 5 °C / min and hold for 2 h;

[0031] The third stage: Heat from 1000 °C to 2000 °C at a rate of 3 °C / min and hold for 4 h;

[0032] The sintered waste is ball-milled and crushed to a particle size of ≤1 μm, and then recycled into the new powder at a ratio of 10%-20%.

[0033] This embodiment uses industrial-grade raw materials, with the cost reduced by 50% compared to 99.99% raw materials; doped with transition metal oxide Mn3O4 to inhibit abnormal grain growth and improve mechanical strength, with a hardness of ≥8 GPa; the forming process uses water-based tape casting to avoid the pollution of toluene and ethanol in traditional processes; sintering aids Bi2O3 and CuO are added during the sintering process to form liquid-phase sintering and reduce the sintering temperature to 1200 °C; the sintering process adopts a three-stage sintering method, where the first stage removes the binder, the second stage achieves preliminary densification, and the third stage realizes complete densification; and after the sintered waste is ball-milled and crushed to a particle size of ≤1 μm, it is recycled into the new powder at a ratio of 10%-20%, and the raw material utilization rate is increased to 90%.

[0034] Performance tests were carried out on the prepared target materials, and the results are shown in the following table:

[0035] Performance test:

[0036] Index Test result Density 96.2％ Grain size 1.8μm Remanent polarization <![CDATA[28μC / cm 2 > Coercive field 13kV / cm Hardness 8.5GPa

[0037] Comparative example 1: Traditional high-pressure sintering was used

[0038] Raw materials: PbO, ZrO2, TiO2 with a purity of 99.99%;

[0039] Process: Hot-press sintering, pressure 30 MPa, temperature 1250 °C;

[0040] Performance: Density 97.5%, and the cost is 2.3 times that of the embodiment.

[0041] Comparative example 2: Undoped normal-pressure sintering

[0042] Raw materials: PZTO with a purity of 99.5%, without dopants;

[0043] Performance: Density 88.7%, grain size 5.2 μm, Pr = 18 μC / cm 2 。

[0044] It can be seen from this that the preparation method of a PZTO target material with low cost, high density, and easy mass production according to the present invention solves the problems of high cost, low density, and poor film performance in traditional processes through the optimization of normal-pressure sintering process, transition metal / rare earth co-doping, and gradient structure design.

[0045] Those of ordinary skill in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the present invention is limited to these examples; under the concept of the present invention, the technical features in the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations in different aspects of the present invention as described above, which are not provided in detail for the sake of brevity. Any omission, modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for preparing a high-density PZTO target by low-cost atmospheric pressure sintering, characterized in that: The following steps are included: Step 1, select industrial-grade raw materials: PbO, ZrO2, TiO2 with a purity of ≥99.5%, and dopants: 0.5-2wt.% of transition metal oxides and 0.1-0.5wt.% of rare earth oxides; Step 2, ball milling the above raw materials and dopants for 24 hours, and then mixing them together after ball milling; Step 3, tape casting the mixed materials; Step 4: The ball-milled raw material and dopant are sintered at normal pressure to obtain the target material. The sintering process includes three stages: In the first stage, the temperature was raised from room temperature to 500°C at a rate of 2°C / min and kept at this temperature for 1h; In the second stage, the temperature was raised from 500°C to 1000°C at a rate of 5°C / min and kept at this temperature for 2h; In the third stage, the temperature was raised from 1000°C to 2000°C at a rate of 3°C / min and kept at this temperature for 4 hours.

2. According to claim 1, a method for preparing a high-density PZTO target by low-cost pressureless sintering, characterized in that: The molar ratio of PbO:ZrO2:TiO2 is 52:28:

20.

3. The method for preparing a high-density PZTO target by low-cost pressureless sintering according to claim 2, characterized in that: The transition metal oxide is Mn3O4, and the rare earth oxide is La2O3.

4. The method for preparing a high-density PZTO target by low-cost pressureless sintering according to claim 1, characterized in that: In the step 2, alcohol is used as the ball milling medium, and the ball-to-material ratio is 5:

1.

5. The method for preparing a high-density PZTO target by low-cost pressureless sintering according to claim 1, characterized in that: The tape casting is water-based tape casting: water is used as solvent and polyvinyl alcohol is used as binder.

6. The method for preparing a high-density PZTO target by low-cost pressureless sintering according to claim 5, characterized in that: After the tape casting in step three, cold isostatic pressing is performed at a pressure of 200 MPa.

7. The method for preparing a high-density PZTO target by low-cost pressureless sintering according to claim 1, characterized in that: In the fourth step, the sintering waste is crushed by ball milling to a particle size of ≤1 μm, and is mixed back into the new powder at a ratio of 10%-20%.

8. The method for preparing a high-density PZTO target by low-cost pressureless sintering according to claim 1, characterized in that: In the fourth step, sintering is performed by adding sintering aids: 0.3-0.8wt.% Bi2O3 and 0.2-0.5wt.% CuO to form liquid phase sintering.