A CaTiO3-LaAlO3-based microwave dielectric ceramic and its preparation method

Abstract

The present invention provides a CaTiO3-LaAlO3-based microwave dielectric ceramic and a preparation method thereof, comprising a main crystal ceramic, a doping phase or a firing-aiding ceramic powder or a combination thereof; the main crystal ceramic is (1-x)CaTiO3-xLaAlO3, 0.30≤x≤0.35; the doping phase is CeO2, and the firing-aiding ceramic powder is Li2ZnTi3O8 ceramic powder, Li2MgTi3O8 ceramic powder, BaZn2Ti4O 11 One or more ceramic powders. The CaTiO3-LaAlO3-based microwave dielectric ceramics of the present invention can be sintered at 1280-1400°C, have good compactness and excellent dielectric properties, a dielectric constant of 40-48, a Q*f value of 20,000-38,000 GHz, and a resonant frequency temperature coefficient of -10-10 ppm / °C. They have practical application value in microwave devices in the communications field.

Description

Technical Field

[0001] The invention belongs to the field of electronic ceramics and their manufacture, and in particular relates to a CaTiO3-LaAlO3 based microwave dielectric ceramic and a preparation method thereof. Background Art

[0002] In the 1980s, wireless communication equipment gradually entered the commercial market and quickly occupied the market. Especially in recent years, with the vigorous development of mobile communication technology, microwave devices have developed towards miniaturization and integration, and more and more microwave dielectric materials have been deeply studied and applied. Perovskite microwave dielectric ceramics have high application value due to their high quality factor, adjustable dielectric constant and temperature coefficient. CaTiO3, as a representative of simple perovskite structure, has a high dielectric constant (ε r =170), but its resonant frequency temperature coefficient is large (τ f = +850ppm / °C), making it difficult to meet the requirements for commercial microwave ceramic materials. CaTiO3 and LaAlO3 crystals have similar ideal perovskite structures. Moon et al., in "Singtering behavior and microwave dielectric properties of (Ca,La)(Ti,Al)O3 ceramics," demonstrated that when 0.4 < x < 0.6, (1-x)CaTiO3-xLaAlO3 forms a pseudocubic solid solution. Therefore, CaTiO3-LaAlO3 solid solution ceramics are expected to become excellent microwave dielectric materials.

[0003] ATiO3-LnAlO3 (A = Sr, Ca, Ln = Nd, La) has the advantages of low dielectric loss, adjustable dielectric constant, and near-zero resonant frequency temperature coefficient. It is a representative material with medium dielectric constant and is widely used in microwave devices such as dielectric antennas, dielectric filters, and phase shifters. This type of material was first proposed by Soviet experts in the 1960s, and the preparation process and electrical properties were reported, but it did not attract attention at the time. In recent years, the multifunctionality of microwave dielectric ceramics has gradually received attention, and this type of material has returned to the hot research field. More and more scholars have studied the relationship between the chemical composition, crystal structure and microwave dielectric properties of CaTiO3-LaAlO3-based dielectric ceramics, but the sintering temperature of CaTiO3-LaAlO3 ceramics is usually higher than 1500℃, which has become an important factor limiting the application of this type of material.

[0004] Although some scholars have proposed using wet chemical methods to prepare ultrafine powders and reduce the sintering temperature of CaTiO3-LaAlO3 ceramics, wet chemical processes are costly and unstable, making them unsuitable for mass production. During the solid-phase synthesis of CaTiO3-LaAlO3 ceramics, the introduction of sintering aids such as Li2O-B2O3-SiO2, 0.76Bi2O3-0.24NiO, and Li2O-B2O3-SiO2+CeO2 effectively reduced the sintering temperature of CaTiO3-LaAlO3 ceramics. However, defects such as pores are prone to appear in CaTiO3-LaAlO3 ceramics prepared by solid-phase reaction sintering, limiting the practical application of this material.

[0005] Therefore, it is necessary to provide an improved technical solution to the above-mentioned deficiencies in the prior art. Summary of the Invention

[0006] In view of the shortcomings of the prior art described above, the object of the present invention is to provide a CaTiO3-LaAlO3-based microwave dielectric ceramic and a preparation method thereof, so as to solve the problems of the prior art CaTiO3-LaAlO3 ceramics such as high sintering temperature, internal pores, poor stability and being unfavorable for mass production.

[0007] To achieve the above-mentioned and other related purposes, the present invention provides a CaTiO3-LaAlO3-based microwave dielectric ceramic, comprising a main crystal ceramic and one or a combination of a doping phase or a sintering-aid ceramic powder;

[0008] The main crystal ceramic is (1-x)CaTiO3-xLaAlO3, 0.30≤x≤0.35; the doping phase is CeO2, and the sintering ceramic powder is Li2ZnTi3O8 ceramic powder, Li2MgTi3O8 ceramic powder, BaZn2Ti4O 11 A mixture of one or more ceramic powders.

[0009] Preferably, the mass ratio of the doped phase to the main crystal ceramic is 0-2wt%, the mass ratio of the sintering-aid ceramic powder to the total mass of the CaTiO3-LaAlO3-based microwave dielectric ceramic is 0-4wt%, and the added amount of the sintering-aid ceramic powder is not zero.

[0010] Preferably, the CaTiO3-LaAlO3-based microwave dielectric ceramic has a sintering temperature of 1280-1400°C, a dielectric constant of 40-48, a Q*f value of 20000-38000 GHz, and a resonant frequency temperature coefficient of -10-10 ppm / °C.

[0011] The present invention also provides a method for preparing CaTiO3-LaAlO3-based microwave dielectric ceramics, the preparation method comprising the following steps:

[0012] S1. Weigh the raw material powders of the main crystal ceramic, CaCO3, TiO2, La2O3, and Al2O3, and add them into a ball mill. Then add CeO2 and perform the first ball milling and mixing. After drying, a mixed main material is obtained.

[0013] S2, calcining the mixed main material at high temperature, then putting it into a ball mill again for a second ball milling, and drying it to obtain (1-x)CaTiO3-xLaAlO3-CeO2 ceramic pre-synthetic powder;

[0014] S3. Put the (1-x)CaTiO3-xLaAlO3-CeO2 ceramic pre-synthesized powder and the sintering-aid ceramic powder into a ball mill for ball milling and mixing, then dry, granulate, and press into shape, and then calcine at high temperature in an air atmosphere to obtain CaTiO3-LaAlO3-based microwave dielectric ceramics.

[0015] Preferably, the sintering ceramic powder in step S3 is Li2ZnTi3O8 ceramic powder, Li2MgTi3O8 ceramic powder, BaZn2Ti4O 11 At least one of ceramic powders.

[0016] Preferably, the amount of the sintering-aid ceramic powder added in step S3 is 0-4 wt% of the total mass of the obtained CaTiO 3 -LaAlO 3 -based microwave dielectric ceramic, and the amount of the sintering-aid ceramic powder added is not zero.

[0017] Preferably, the preparation method of the Li2ZnTi3O8 ceramic powder includes: weighing Li2CO3, ZnO, and TiO2 in a molar ratio of 1:1:3, ball-milling and mixing, drying, calcining at 850-950°C for 4-6h, and then ball-milling and drying to obtain Li2ZnTi3O8 ceramic powder.

[0018] Preferably, the preparation method of the Li2MgTi3O8 ceramic powder includes: weighing Li2CO3, MgO, and TiO2 in a molar ratio of 1:1:3, ball-milling and mixing, drying, calcining at 850-950°C for 4-6h, and then ball-milling and drying to obtain Li2MgTi3O8 ceramic powder.

[0019] Preferably, the BaZn2Ti4O 11 The preparation method of ceramic powder comprises: weighing BaCO3, ZnO and TiO2 in a molar ratio of 1:2:4, mixing by ball milling, drying, calcining at 900-1000°C for 4-6 hours, and then ball milling and drying to obtain BaZn2Ti4O 11 Ceramic powder.

[0020] Preferably, in step S1, the raw material powders CaCO3, TiO2, La2O3, and Al2O3 are weighed according to the molar ratio of the main crystal ceramic (1-x)CaTiO3-xLaAlO3, wherein 0.30≤x≤0.35; and the added amount of CeO2 is 0-2wt% of the total mass of the main crystal ceramic.

[0021] Preferably, the temperature of the high-temperature calcination in step S2 is 1100-1250° C., and the time of the high-temperature calcination is 4-6 hours.

[0022] Preferably, an adhesive needs to be added before granulation in step S3, and the adhesive is one of PVA, PVB or sodium polyacrylate.

[0023] Preferably, the pressing pressure is 6-7 MPa.

[0024] Preferably, the high-temperature calcination step includes: first heating from room temperature to 550-650°C at a heating rate of 2°C / min, and keeping warm for 2 hours; then heating to 1280-1400°C at a heating rate of 5°C / min, and keeping warm for 4 hours.

[0025] As described above, the CaTiO3-LaAlO3-based microwave dielectric ceramics and the preparation method thereof of the present invention have the following beneficial effects:

[0026] The present invention effectively improves Ti by introducing CeO2 into the main crystal ceramic (1-x)CaTiO3-xLaAlO3 4+ It is easily reduced to Ti during the sintering process 3+ The problem of oxygen vacancies is beneficial to improve the densification of ceramics; due to the sintering of ceramic powder Li2ZnTi3O8, Li2MgTi3O8 or BaZn2Ti4O 11 Ceramic powder has a low melting point and can promote the sintering of CaTiO3-LaAlO3 ceramics. In addition, Li2ZnTi3O8, Li2MgTi3O8 or BaZn2Ti4O 11 The ceramic powder and the main crystal ceramic produce a small amount of Al-rich second phase, which reduces the distribution range of the CaTiO3-LaAlO3 ceramic grains, further improves the densification degree of the ceramic, and thus increases the dielectric constant of the CaTiO3-LaAlO3 ceramic; at the same time, the raw materials for the firing-aid ceramics are all common oxides, which are cheap and easy to obtain, pollution-free, and the preparation method is simple.

[0027] The CaTiO3-LaAlO3-based microwave dielectric ceramics of the present invention can be sintered at 1280-1400°C, have good compactness and excellent dielectric properties, a dielectric constant of 40-48, a Q*f value of 20,000-38,000 GHz, and a resonant frequency temperature coefficient of -10-10 ppm / °C, and have practical application value in microwave devices in the communication field. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 Shown is a surface SEM image of the CaTiO3-LaAlO3 based microwave dielectric ceramic prepared in specific embodiment 6 of the present invention.

[0029] Figure 2 Shown is a cross-sectional SEM image of the CaTiO3-LaAlO3-based microwave dielectric ceramic prepared in specific embodiment 6 of the present invention.

[0030] Figure 3 Shown is a surface SEM image of the CaTiO3-LaAlO3-based microwave dielectric ceramic prepared in specific embodiment 7 of the present invention.

[0031] Figure 4 Shown is a cross-sectional SEM image of the CaTiO3-LaAlO3-based microwave dielectric ceramic prepared in specific embodiment 7 of the present invention.

[0032] Figure 5 Shown is a surface SEM image of a CaTiO3-LaAlO3 based microwave dielectric ceramic prepared in a comparative example in a specific embodiment of the present invention.

[0033] Figure 6 Shown is a cross-sectional SEM image of a CaTiO3-LaAlO3-based microwave dielectric ceramic prepared in a comparative example in a specific embodiment of the present invention. DETAILED DESCRIPTION

[0034] The following describes the embodiments of the present invention through specific examples. Those skilled in the art will readily understand the other advantages and benefits of the present invention from the disclosure herein. The present invention may also be implemented or applied through various other specific embodiments, and the details in this specification may be modified or altered based on different viewpoints and applications without departing from the spirit of the present invention.

[0035] The present invention provides a CaTiO3-LaAlO3-based microwave dielectric ceramic, comprising a main crystal ceramic, and also comprising one or a combination of a doping phase or a firing-aid ceramic; the main crystal ceramic is (1-x)CaTiO3-xLaAlO3, 0.30≤x≤0.35, the doping phase is CeO2, and the firing-aid ceramic powder is Li2ZnTi3O8 ceramic powder, Li2MgTi3O8 ceramic powder, BaZn2Ti4O 11A mixture of one or more ceramic powders.

[0036] Specifically, x may include values ​​in any range such as 0.30, 0.31, 0.32, 0.33, 0.34, and 0.35.

[0037] As an example, the mass ratio of the doped phase to the main crystal ceramic is 0-2wt%, the mass ratio of the sintering ceramic powder to the total mass of the CaTiO3-LaAlO3 based microwave dielectric ceramic is 0-4wt%, and the added amount of the sintering ceramic powder is not zero.

[0038] Specifically, the mass ratio of the doped phase to the main crystal ceramic can include values ​​within any range, such as 0, 0.1wt%, 0.5wt%, 1wt%, 1.5wt%, 2wt%, etc., and the mass ratio of the sintering-aid ceramic powder to the total mass of the CaTiO3-LaAlO3-based microwave dielectric ceramic can include values ​​within any range, such as 0, 0.5wt%, 1wt%, 2wt%, 3wt%, 4wt%, etc.; but the amount of sintering-aid ceramic added is not 0.

[0039] CeO2 effectively improves Ti 4+ It is easily reduced to Ti during the sintering process 3+ To solve the problem of oxygen vacancies, the sintering ceramics Li2ZnTi3O8, Li2MgTi3O8, BaZn2Ti4O 11 The composite ceramics are formed, which effectively improves the grain uniformity of the CaTiO3-LaAlO3 based microwave dielectric ceramics and improves the comprehensive dielectric properties of the CaTiO3-LaAlO3 based microwave dielectric ceramics.

[0040] As an example, the sintering temperature of CaTiO3-LaAlO3-based microwave dielectric ceramics is 1280-1400°C, the dielectric constant is 40-48, the Q*f value is 20000-38000 GHz, and the resonant frequency temperature coefficient is -10-10 ppm / °C.

[0041] The present invention also provides a method for preparing CaTiO3-LaAlO3-based microwave dielectric ceramics, which comprises the following steps:

[0042] S1. Weigh the raw material powders of the main crystal ceramic, CaCO3, TiO2, La2O3, and Al2O3, and add them into a ball mill. Then add CeO2 and perform the first ball milling and mixing. After drying, a mixed main material is obtained.

[0043] S2, calcining the mixed main material at high temperature, then putting it into the ball mill again for a second ball milling, and drying it to obtain (1-x)CaTiO3-xLaAlO3-CeO2 ceramic pre-synthetic powder;

[0044] S3. Place (1-x)CaTiO3-xLaAlO3-CeO2 ceramic pre-synthesized powder and sintering-aid ceramic powder into a ball mill for ball milling and mixing. Add an adhesive to the dried mixture, then granulate and press into shape. Then, calcinate at high temperature in an air atmosphere to obtain CaTiO3-LaAlO3-based microwave dielectric ceramics.

[0045] Specifically, during the first ball milling, zirconium oxide grinding balls and deionized water are added to the ball mill jar. In step S1, the mass ratio of the mixed main material, grinding balls and deionized water is 1:2:1. The first ball milling time is 2 to 4 hours, the drying temperature is 80°C, and the drying time is 6 to 10 hours. In step S2, the second ball milling time is 3 to 5 hours, the ball milling medium is deionized water, and the drying conditions are the same as those in step S1. In step S3, the ball milling medium is deionized water, and the drying conditions are 80°C for 6 to 10 hours.

[0046] In addition, the pressing molding in step S3 is preferably cylindrical. In a specific embodiment, the pressing molding is performed into a cylinder with a diameter of 15 mm and a height of 6 mm.

[0047] As an example, the ceramic powders used in step S3 to aid sintering are Li2ZnTi3O8 ceramic powder, Li2MgTi3O8 ceramic powder, BaZn2Ti4O 11 At least one of ceramic powders.

[0048] Specifically, Li2ZnTi3O8 ceramic powder, Li2MgTi3O8 ceramic powder, BaZn2Ti4O 11 Ceramic powder has a low melting point and can promote the sintering of CaTiO3-LaAlO3 ceramics. In addition, Li2ZnTi3O8 ceramic powder, Li2MgTi3O8 ceramic powder, BaZn2Ti4O 11 The ceramic powder and the main crystal ceramic produce a small amount of Al-rich second phase, which reduces the distribution range of CaTiO3-LaAlO3 ceramic grains and improves the densification degree of the ceramic, thereby increasing the dielectric constant of the CaTiO3-LaAlO3 based microwave dielectric ceramics.

[0049] As an example, the amount of the sintering-aid ceramic powder added in step S3 is 0-4 wt % of the total mass of the obtained CaTiO 3 -LaAlO 3 -based microwave dielectric ceramic, and the amount of the sintering-aid ceramic powder added is not zero.

[0050] Specifically, the amount of the sintering-aid ceramic powder added is a value within any range such as 0.5wt%, 1wt%, 2wt%, 3wt%, 4wt% of the total mass of the obtained CaTiO3-LaAlO3-based microwave dielectric ceramic, and can be adjusted according to actual conditions.

[0051] As an example, a method for preparing Li2ZnTi3O8 ceramic powder includes: weighing Li2CO3, ZnO, and TiO2 in a molar ratio of 1:1:3, ball-milling and mixing, drying, calcining at 850-950°C (e.g., 850°C, 870°C, 890°C, 900°C, 920°C, 940°C, 950°C, etc.) for 4-6 hours (e.g., 4 hours, 4.5 hours, 5 hours, 5.5 hours, 6 hours, etc.), and then ball-milling and drying to obtain Li2ZnTi3O8 ceramic powder;

[0052] The preparation method of Li2MgTi3O8 ceramic powder includes: weighing Li2CO3, MgO, and TiO2 in a molar ratio of 1:1:3, ball-milling and mixing, drying, calcining at 850-950°C (e.g., 850°C, 870°C, 890°C, 900°C, 920°C, 940°C, 950°C, etc.) for 4-6 hours (e.g., 4 hours, 4.5 hours, 5 hours, 5.5 hours, 6 hours, etc.), and then ball-milling and drying to obtain Li2MgTi3O8 ceramic powder;

[0053] BaZn2Ti4O 11 The preparation method of ceramic powder includes: weighing BaCO3, ZnO, and TiO2 in a molar ratio of 1:2:4, ball milling and mixing, drying, calcining at 900-1000°C (such as 900°C, 920°C, 940°C, 960°C, 980°C, 1000°C, etc.) for 4-6 hours (such as 4 hours, 4.5 hours, 5 hours, 5.5 hours, 6 hours, etc.), and then ball milling and drying to obtain BaZn2Ti4O 11 Ceramic powder.

[0054] Specifically, in the preparation methods of the above three ceramic powders, zirconium oxide grinding balls and deionized water are added to the ball mill during the ball milling mixing process, with the material: ball: deionized water = 1:2:1, and the ball milling mixing is carried out for 2 to 4 hours, and the drying conditions are 80°C for 6 to 10 hours; after calcination, the ball milling is carried out again for 3 to 5 hours, and the powder is dried at 80°C for 6 to 10 hours.

[0055] As an example, in step S1, the raw material powders CaCO3, TiO2, La2O3, and Al2O3 are weighed according to the molar ratio of the main crystal ceramic (1-x)CaTiO3-xLaAlO3, where 0.30≤x≤0.35; the added amount of CeO2 is 0~2wt% of the total mass of the main crystal ceramic.

[0056] Specifically, the raw material powders CaCO3, TiO2, La2O3, and Al2O3 are weighed according to the molar ratio of the main crystal ceramic (1-x)CaTiO3-xLaAlO3. In fact, the raw material powders CaCO3, TiO2, La2O3, and Al2O3 are weighed according to the molar ratio of (1-x): (1-x): 0.5x: 0.5x, and x can include a value in any range such as 0.30, 0.31, 0.32, 0.33, 0.34, and 0.35; the mass ratio of the addition amount of CeO2 to the total mass of the main crystal ceramic can include a value in any range such as 0, 0.1wt%, 0.5wt%, 1wt%, 1.5wt%, and 2wt%; a small amount of Ce 4+ The introduction of Ti 4+ The valence change occurs, which reduces the generation of oxygen vacancies and is beneficial to improving the densification of ceramics.

[0057] As an example, the temperature of high-temperature calcination in step S2 is 1100-1250° C., and the time of high-temperature calcination is 4-6 hours.

[0058] Specifically, the temperature of the high-temperature calcination in step S2 may include a value within any range such as 1100°C, 1150°C, 1200°C, 1250°C, etc., which can be adjusted according to actual conditions; the time of the high-temperature calcination may include a value within any range such as 4h, 4.5h, 5h, 5.5h, 6h, etc., which can be adjusted according to actual conditions.

[0059] As an example, the adhesive in step S3 is one of PVA (polyvinyl alcohol), PVB (polyvinyl butyral) or sodium polyacrylate.

[0060] As an example, the pressure of the pressing in step S3 is 6 to 7 MPa.

[0061] Specifically, the pressure for press molding may include values ​​within any range such as 6 MPa, 6.2 MPa, 6.4 MPa, 6.6 MPa, 6.8 MPa, 7 MPa, etc., and may be adjusted according to actual conditions.

[0062] As an example, the high-temperature calcination step in step S3 includes: first heating from room temperature to 550-650°C (such as 550°C, 580°C, 600°C, 620°C, 650°C, etc.) at a heating rate of 2°C / min, and keeping warm for 2 hours; then heating to 1280-1400°C (such as 1280, 1300, 1350, 1400, etc.) at a heating rate of 5°C / min, and keeping warm for 4 hours.

[0063] In order to better understand the CaTiO3-LaAlO3-based microwave dielectric ceramics and the preparation method thereof in the present invention, the CaTiO3-LaAlO3-based microwave dielectric ceramics and the preparation method thereof in the present invention are described below with reference to specific embodiments. It should be noted that these embodiments are merely illustrative and do not limit the present invention in any way.

[0064] The preparation method of the sintering-aid ceramic powder used in the following Examples 1 to 12 is as follows:

[0065] The preparation method of Li2ZnTi3O8 ceramic powder or Li2MgTi3O8 ceramic powder is as follows: Li2CO3, ZnO (MgO), and TiO2 are weighed in a molar ratio of 1:1:3, ball-milled and mixed, dried, calcined at 850°C for 4 hours, and then ball-milled for 5 hours, and dried at 80°C for 8 hours to obtain Li2ZnTi3O8 ceramic powder.

[0066] BaZn2Ti4O 11 The preparation method of ceramic powder is as follows: BaCO3, ZnO and TiO2 are weighed in a molar ratio of 1:2:4, ball-milled and mixed, dried, calcined at 900℃ for 4h, ball-milled for 5h, and dried at 80℃ for 8h to obtain BaZn2Ti4O 11 Ceramic powder

[0067] Example 1

[0068] This embodiment provides a CaTiO3-LaAlO3-based microwave dielectric ceramic, including a main crystal ceramic and a firing-aid ceramic powder; the main crystal ceramic is 0.7CaTiO3-0.3LaAlO3, the firing-aid ceramic powder is Li2MgTi3O8 ceramic powder, and the mass ratio of the firing-aid ceramic powder to the total mass of the CaTiO3-LaAlO3-based microwave dielectric ceramic is 1wt%.

[0069] This embodiment also provides a method for preparing a CaTiO3-LaAlO3-based microwave dielectric ceramic, comprising the following steps:

[0070] S1. Weigh the raw material powders of the main crystal ceramic, CaCO3, TiO2, La2O3, and Al2O3, in a molar ratio of 0.7:0.7:0.15:0.15, and add them to a nylon ball mill, and perform the first ball milling for 2 h (the mixing ball milling medium is deionized water, and the mass ratio of the mixed main material to the grinding balls and deionized water is 1:2:1), and then dry them at 80°C for 8 h to obtain the mixed main material;

[0071] S2, the mixed main material was calcined in a muffle furnace at 1100 ° C for 4 hours, and then placed in a nylon ball mill for a second ball milling for 5 hours (the mixed ball milling medium was deionized water, and the mass ratio of the mixed main material to the grinding balls to the deionized water was 1:2:1), and then dried at 80 ° C for 8 hours to obtain a ceramic pre-synthetic powder;

[0072] S3. The ceramic pre-synthesized powder and the sintering-aid ceramic powder (Li2MgTi3O8 ceramic powder) (the mass ratio of the sintering-aid ceramic powder to the total mass of the CaTiO3-LaAlO3-based microwave dielectric ceramic is 1wt%) are placed in a ball mill for ball milling mixing (the ball milling medium is deionized water), and then dried at 80°C for 8h. PVA is added to the dried powder for granulation, and pressed into a cylinder with a diameter of 15mm and a height of 6mm at 6Mpa. The pressed cylinder is then placed in a muffle furnace, and first heated from room temperature to 550°C at a heating rate of 2° / min in an air atmosphere, and kept warm for 2 hours to remove organic matter in the sample. The temperature is then heated to 1400°C at a heating rate of 5° / min, and kept warm for 4 hours to obtain CaTiO3-LaAlO3-based microwave dielectric ceramics.

[0073] Example 2

[0074] This embodiment provides a CaTiO3-LaAlO3-based microwave dielectric ceramic, including a main crystal ceramic and a firing-aid ceramic powder; the main crystal ceramic is 0.65CaTiO3-0.35LaAlO3, and the firing-aid ceramic powder is Li2ZnTi3O8 ceramic powder; the mass ratio of the firing-aid ceramic powder to the total mass of the CaTiO3-LaAlO3-based microwave dielectric ceramic is 1wt%.

[0075] This embodiment also provides a preparation method of CaTiO3-LaAlO3-based microwave dielectric ceramics, which differs from that in Example 1 in that: in step S1, the raw material powders of the main crystal ceramic, CaCO3, TiO2, La2O3, and Al2O3, are weighed according to a molar ratio of 0.65:0.65:0.175:0.175; the auxiliary sintering ceramic powder in step S3 is Li2ZnTi3O8 ceramic powder. Other methods and steps are the same as those in Example 1 and are not repeated here.

[0076] Example 3

[0077] This embodiment provides a CaTiO3-LaAlO3-based microwave dielectric ceramic, including a main crystal ceramic, a doping phase and a firing-aid ceramic; the main crystal ceramic is 0.65CaTiO3-0.35LaAlO3, the doping phase is CeO2, and the firing-aid ceramic powder is Li2ZnTi3O8 ceramic powder; the mass ratio of the doping phase to the main crystal ceramic is 1wt%, and the mass ratio of the firing-aid ceramic powder to the total mass of the CaTiO3-LaAlO3-based microwave dielectric ceramic is 1wt%.

[0078] This embodiment also provides a preparation method of CaTiO3-LaAlO3-based microwave dielectric ceramics, which differs from that in Example 2 in that: in step S1, the raw material powders of the main crystal ceramic, CaCO3, TiO2, La2O3, and Al2O3, are weighed according to a molar ratio of 0.65:0.65:0.175:0.175, and are added to a nylon ball mill, and then CeO2 is added (the amount of CeO2 added is 1wt% of the total mass of the main crystal ceramic); the other steps and methods are the same as those in Example 2 and are not repeated here.

[0079] Example 4

[0080] This embodiment provides a CaTiO3-LaAlO3-based microwave dielectric ceramic, including a main crystal ceramic, a doping phase and a firing-aid ceramic; the main crystal ceramic is 0.65CaTiO3-0.35LaAlO3, the doping phase is CeO2, and the firing-aid ceramic powder is Li2ZnTi3O8 ceramic powder; the mass ratio of the doping phase to the main crystal ceramic is 2wt%, and the mass ratio of the firing-aid ceramic powder to the total mass of the CaTiO3-LaAlO3-based microwave dielectric ceramic is 1wt%.

[0081] This embodiment also provides a method for preparing CaTiO3-LaAlO3-based microwave dielectric ceramics. The preparation method is different from that in Example 3 in that the amount of CeO2 added in step S1 is 2wt% of the total mass of the raw material powder; the other steps and methods are the same as those in Example 3 and are not repeated here.

[0082] Example 5

[0083] This embodiment provides a CaTiO3-LaAlO3-based microwave dielectric ceramic, including a main crystal ceramic, a doping phase and a firing-aid ceramic; the main crystal ceramic is 0.65CaTiO3-0.35LaAlO3, the doping phase is CeO2, and the firing-aid ceramic powder is Li2ZnTi3O8 ceramic powder; the mass ratio of the doping phase to the main crystal ceramic is 1wt%, and the mass ratio of the firing-aid ceramic powder to the total mass of the CaTiO3-LaAlO3-based microwave dielectric ceramic is 1.5wt%.

[0084] This embodiment also provides a method for preparing a CaTiO3-LaAlO3-based microwave dielectric ceramic. The difference between the preparation method and that in Example 3 is that the mass ratio of the sintering-aid ceramic powder to the total mass of the CaTiO3-LaAlO3-based microwave dielectric ceramic in step S3 is 1.5wt%; the other steps and methods are the same as those in Example 3 and are not repeated here.

[0085] Example 6

[0086] This embodiment provides a CaTiO3-LaAlO3-based microwave dielectric ceramic, including a main crystal ceramic, a doping phase and a firing-aid ceramic; the main crystal ceramic is 0.65CaTiO3-0.35LaAlO3, the doping phase is CeO2, and the firing-aid ceramic powder is Li2ZnTi3O8 ceramic powder or Li2MgTi3O8 ceramic powder; the mass ratio of the doping phase to the main crystal ceramic is 1wt%, and the mass ratio of the firing-aid ceramic powder to the total mass of the CaTiO3-LaAlO3-based microwave dielectric ceramic is 2wt%.

[0087] This embodiment also provides a method for preparing a CaTiO3-LaAlO3-based microwave dielectric ceramic. The difference between the preparation method and that in Example 5 is that the mass ratio of the sintering-aid ceramic powder to the total mass of the CaTiO3-LaAlO3-based microwave dielectric ceramic in step S3 is 2 wt %. The other steps and methods are the same as those in Example 5 and will not be repeated here.

[0088] See Figure 1 、 Figure 2 Shown are SEM images of the surface and cross-section of the CaTiO3-LaAlO3-based microwave dielectric ceramic prepared in this embodiment. It can be seen from the figure that the grains on the ceramic surface are closely arranged, the surface is dense and has no obvious pores, and there is an obvious aluminum-rich second phase. This second phase can also be observed in the ceramic cross-section. This second phase may be caused by the introduction of sintering aid ceramic powder; compared with the comparative example, the grain size of the CaTiO3-LaAlO3-based microwave dielectric ceramic prepared in this embodiment is reduced, the pore volume of the ceramic cross-section is significantly reduced, and the ceramic density is significantly improved.

[0089] Example 7

[0090] This embodiment provides a CaTiO3-LaAlO3-based microwave dielectric ceramic, including a main crystal ceramic, a doping phase and a firing-aid ceramic; the main crystal ceramic is 0.65CaTiO3-0.35LaAlO3, the doping phase is CeO2, and the firing-aid ceramic powder is Li2ZnTi3O8 ceramic powder; the mass ratio of the doping phase to the main crystal ceramic is 1wt%, and the mass ratio of the firing-aid ceramic powder to the total mass of the CaTiO3-LaAlO3-based microwave dielectric ceramic is 2.5wt%.

[0091] This embodiment also provides a method for preparing a CaTiO3-LaAlO3-based microwave dielectric ceramic. The difference between the preparation method and that in Example 5 is that the mass ratio of the sintering-aid ceramic powder to the total mass of the CaTiO3-LaAlO3-based microwave dielectric ceramic in step S3 is 2.5wt%; the other steps and methods are the same as those in Example 5 and will not be repeated here.

[0092] See Figure 3 、 Figure 4The following are SEM images of the surface and cross section of the CaTiO3-LaAlO3 based microwave dielectric ceramic prepared in this embodiment. Figure 3 This shows that the ceramic surface is dense and has no obvious pores. Figure 1 In comparison, the grain size in this embodiment tends to increase, and the Al-rich second phase increases; Figure 4 This shows that the interior of the ceramics prepared in this embodiment is relatively dense without large pores, which also shows that the introduction of appropriate amounts of dopants and sintering aids can improve the density of CaTiO3-LaAlO3-based microwave dielectric ceramics.

[0093] Example 8

[0094] This embodiment provides a CaTiO3-LaAlO3-based microwave dielectric ceramic, including a main crystal ceramic, a doping phase and a firing-aid ceramic; the main crystal ceramic is 0.65CaTiO3-0.35LaAlO3, the doping phase is CeO2, and the firing-aid ceramic powder is Li2ZnTi3O8 ceramic powder; the mass ratio of the doping phase to the main crystal ceramic is 1.5wt%, and the mass ratio of the firing-aid ceramic powder to the total mass of the CaTiO3-LaAlO3-based microwave dielectric ceramic is 3wt%.

[0095] This embodiment also provides a preparation method of CaTiO3-LaAlO3-based microwave dielectric ceramics, which differs from that in Example 3 in that: the amount of CeO2 added in step S1 is 1.5wt% of the total mass of the raw material powder; the mass ratio of the sintering-aid ceramic powder to the total mass of the CaTiO3-LaAlO3-based microwave dielectric ceramics in step S3 is 3wt%; the other steps and methods are the same as those in Example 3 and are not repeated here.

[0096] Example 9

[0097] This embodiment provides a CaTiO3-LaAlO3-based microwave dielectric ceramic, including a main crystal ceramic, a doping phase and a firing-aid ceramic; the main crystal ceramic is 0.65CaTiO3-0.35LaAlO3, the doping phase is CeO2, and the firing-aid ceramic powder is Li2ZnTi3O8 ceramic powder; the mass ratio of the doping phase to the main crystal ceramic is 1.5wt%, and the mass ratio of the firing-aid ceramic powder to the total mass of the CaTiO3-LaAlO3-based microwave dielectric ceramic is 3.5wt%.

[0098] This embodiment also provides a method for preparing a CaTiO3-LaAlO3-based microwave dielectric ceramic. The difference between the preparation method and that in Example 8 is that the mass ratio of the sintering-aid ceramic powder to the total mass of the CaTiO3-LaAlO3-based microwave dielectric ceramic in step S3 is 3.5wt%; the other steps and methods are the same as those in Example 8 and will not be repeated here.

[0099] Example 10

[0100] This embodiment provides a CaTiO3-LaAlO3-based microwave dielectric ceramic, including a main crystal ceramic, a doping phase and a firing-aid ceramic; the main crystal ceramic is 0.65CaTiO3-0.35LaAlO3, the doping phase is CeO2, and the firing-aid ceramic powder is Li2ZnTi3O8 ceramic powder; the mass ratio of the doping phase to the main crystal ceramic is 1.5wt%, and the mass ratio of the firing-aid ceramic powder to the total mass of the CaTiO3-LaAlO3-based microwave dielectric ceramic is 4wt%.

[0101] This embodiment also provides a method for preparing a CaTiO3-LaAlO3-based microwave dielectric ceramic. The difference between the preparation method and that in Example 8 is that the mass ratio of the sintering-aid ceramic powder to the total mass of the CaTiO3-LaAlO3-based microwave dielectric ceramic in step S3 is 4wt%; the other steps and methods are the same as those in Example 8 and will not be repeated here.

[0102] Example 11

[0103] This embodiment provides a CaTiO3-LaAlO3 based microwave dielectric ceramic, including a main crystal ceramic, a doping phase and a firing aid ceramic; the main crystal ceramic is 0.65CaTiO3-0.35LaAlO3, the doping phase is CeO2, and the firing aid ceramic powder is BaZn2Ti4O 11 Ceramic powder; the mass ratio of the doping phase to the main crystal ceramic is 1.5wt%, and the mass ratio of the sintering ceramic powder to the total mass of the CaTiO3-LaAlO3-based microwave dielectric ceramic is 2wt%.

[0104] This embodiment also provides a method for preparing CaTiO3-LaAlO3-based microwave dielectric ceramics. The difference between the preparation method and that in Example 8 is that the sintering-aid ceramic powder added in step S3 is BaZn2Ti4O 11 Ceramic powder, and BaZn2Ti4O 11 The mass ratio of the ceramic powder to the total mass of the CaTiO 3 -LaAlO 3 -based microwave dielectric ceramic is 2 wt %; the other steps and methods are the same as those in Example 8 and will not be repeated here.

[0105] Example 12

[0106] This embodiment provides a CaTiO3-LaAlO3 based microwave dielectric ceramic, including a main crystal ceramic, a doping phase and a firing aid ceramic; the main crystal ceramic is 0.65CaTiO3-0.35LaAlO3, the doping phase is CeO2, and the firing aid ceramic powder is BaZn2Ti4O 11 Ceramic powder; the mass ratio of the doping phase to the main crystal ceramic is 1.5wt%, and the mass ratio of the sintering ceramic powder to the total mass of the CaTiO3-LaAlO3-based microwave dielectric ceramic is 3wt%.

[0107] This embodiment also provides a method for preparing CaTiO3-LaAlO3-based microwave dielectric ceramics. The difference between the preparation method and that in Example 8 is that the sintering-aid ceramic powder added in step S3 is BaZn2Ti4O 11 Ceramic powder, and BaZn2Ti4O 11 The mass ratio of the ceramic powder to the total mass of the CaTiO 3 -LaAlO 3 -based microwave dielectric ceramic is 3 wt %; the other steps and methods are the same as those in Example 8 and will not be repeated here.

[0108] Comparative Example 1

[0109] This comparative example provides a CaTiO3-LaAlO3 ceramic, the preparation method of which comprises the following steps:

[0110] S1. Weigh the raw material powders of the main crystal ceramic, CaCO3, TiO2, La2O3, and Al2O3, at a molar ratio of 0.65:0.65:0.175:0.175, and add them to a nylon ball mill. Perform the first ball milling for 2 h (the mixing ball milling medium is deionized water, and the mass ratio of the mixed main material to the grinding balls and deionized water is 1:2:1). Then, dry them at 80°C for 8 h to obtain the mixed main material.

[0111] S2, the mixed main material was calcined in a muffle furnace at 1100 ° C for 4 hours, and then placed in a nylon ball mill for a second ball milling for 5 hours (the mixed ball milling medium was deionized water, and the mass ratio of the mixed main material to the grinding balls to the deionized water was 1:2:1), and then dried at 80 ° C for 8 hours to obtain a ceramic pre-synthetic powder;

[0112] S3. PVA was added to the ceramic pre-synthesized powder for granulation, and the mixture was pressed into a cylinder with a diameter of 15 mm and a height of 6 mm at 6 MPa. The pressed cylinder was then placed in a muffle furnace. The temperature was first increased from room temperature to 550°C at a heating rate of 2° / min in an air atmosphere, and kept at this temperature for 2 hours to remove organic matter in the sample. The temperature was then increased to 1500°C at a heating rate of 5° / min and kept at this temperature for 4 hours to obtain CaTiO3-LaAlO3 ceramics.

[0113] See Figure 5 、 Figure 6 Shown are SEM images of the surface and cross-section of the CaTiO3-LaAlO3-based microwave dielectric ceramic prepared in Comparative Example 1. There are no obvious pores on the ceramic surface, no second phase exists, and the grains are relatively coarse. However, there are many pores inside and the density is poor.

[0114] Performance Testing

[0115] The microwave dielectric properties of the CaTiO3-LaAlO3-based microwave dielectric ceramics in Examples 1 to 12 and the CaTiO3-LaAlO3 ceramic in Control Example 1 were evaluated using a cylindrical dielectric resonator method. The open cavity method according to GB / T7265.2-1987 was used to evaluate the microwave dielectric properties of the ceramics. The sintering temperature, dielectric constant, Q*f value, and resonant frequency temperature coefficient of each ceramic were obtained, as shown in Table 1.

[0116] Table 1. Evaluation results of microwave dielectric properties of CaTiO3-LaAlO3-based microwave dielectric ceramics in Examples 1 to 12

[0117]

[0118]

[0119] In summary, the present invention effectively improves Ti by introducing CeO2 into the main crystal ceramic (1-x)CaTiO3-xLaAlO3 4+ It is easily reduced to Ti during the sintering process 3+ The problem of oxygen vacancies is beneficial to improve the densification of ceramics; due to the sintering of ceramic powder Li2ZnTi3O8, Li2MgTi3O8 or BaZn2Ti4O 11 Ceramic powder has a low melting point and can promote the sintering of CaTiO3-LaAlO3 ceramics. In addition, Li2ZnTi3O8, Li2MgTi3O8 or BaZn2Ti4O 11 The ceramic powder and the main crystal ceramic produce a small amount of Al-rich secondary phase, which reduces the distribution range of the CaTiO3-LaAlO3 ceramic grains, further improves the ceramic densification, and thus increases the dielectric constant of the CaTiO3-LaAlO3 ceramic. Furthermore, the raw materials used to aid in firing the ceramic are all commonly available oxides, which are inexpensive, readily available, pollution-free, and simple to prepare. The CaTiO3-LaAlO3-based microwave dielectric ceramic of the present invention can be sintered at 1280-1400°C, exhibits good density, and exhibits excellent dielectric properties, with a dielectric constant of 40-48, a Q*f value of 20,000-38,000 GHz, and a resonant frequency temperature coefficient of -10-10 ppm / °C. This ceramic has practical application value in microwave devices in the communications field. Therefore, the present invention effectively overcomes the various shortcomings of the prior art and has high industrial application value.

[0120] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the present invention. Anyone skilled in the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by one of ordinary skill in the art without departing from the spirit and technical principles disclosed herein are intended to be covered by the claims of the present invention.

Claims

1. A CaTiO3-LaAlO3-based microwave dielectric ceramic, characterized in that: It includes a main crystal ceramic and also includes a combination of a doping phase and a firing-aid ceramic powder; The main crystal ceramic is (1-x)CaTiO3-xLaAlO3, 0.30≤x≤0.35; the doping phase is CeO2, and the sintering ceramic powder is Li2ZnTi3O8 ceramic powder, Li2MgTi3O8 ceramic powder, BaZn2Ti4O 11 A mixture of one or more ceramic powders; the mass ratio of the doped phase to the main crystal ceramic is 0~2wt%, the mass ratio of the sintering-aid ceramic powder to the total mass of the CaTiO3-LaAlO3-based microwave dielectric ceramic is 0~4wt%, and the addition amount of the sintering-aid ceramic powder is not 0.

2. The CaTiO3-LaAlO3-based microwave dielectric ceramic according to claim 1, characterized in that: The CaTiO3-LaAlO3-based microwave dielectric ceramic has a sintering temperature of 1280-1400°C, a dielectric constant of 40-48, a Q*f value of 20000-38000 GHz, and a resonant frequency temperature coefficient of -10-10 ppm / °C.

3. A method for preparing CaTiO3-LaAlO3-based microwave dielectric ceramics, characterized in that: The preparation method comprises the following steps: S1, weighing raw material powders of the main crystal ceramic, CaCO3, TiO2, La2O3, and Al2O3, adding them into a ball mill, then adding CeO2, performing a first ball milling and mixing, and drying to obtain a mixed main material; the raw material powders CaCO3, TiO2, La2O3, and Al2O3 in step S1 are weighed according to the molar ratio of the main crystal ceramic (1-x)CaTiO3-xLaAlO3, wherein 0.30≤x≤0.35; the amount of CeO2 added is 0-2wt% of the total mass of the main crystal ceramic; S2, calcining the mixed main material at high temperature, then putting it into a ball mill again for a second ball milling, and drying it to obtain (1-x)CaTiO3-xLaAlO3-CeO2 ceramic pre-synthetic powder; S3, the (1-x)CaTiO3-xLaAlO3-CeO2 ceramic pre-synthesized powder and the sintering ceramic powder are placed in a ball mill for ball milling and mixing, and then dried, granulated, and pressed into shape, and then calcined at high temperature in an air atmosphere to obtain CaTiO3-LaAlO3-based microwave dielectric ceramics; the sintering ceramic powder in step S3 is Li2ZnTi3O8 ceramic powder, Li2MgTi3O8 ceramic powder, BaZn2Ti4O 11 At least one of the ceramic powders; the amount of the sintering-aid ceramic powder added in step S3 is 0~4wt% of the total mass of the obtained CaTiO3-LaAlO3-based microwave dielectric ceramic, and the amount of the sintering-aid ceramic powder added is not 0.

4. The preparation method according to claim 3, wherein: Includes one or a combination of the following conditions: The preparation method of the Li2ZnTi3O8 ceramic powder comprises: weighing Li2CO3, ZnO, and TiO2 in a molar ratio of 1:1:3, ball-milling and mixing, drying, calcining at 850-950°C for 4-6 hours, and then ball-milling and drying to obtain the Li2ZnTi3O8 ceramic powder; The preparation method of the Li2MgTi3O8 ceramic powder comprises: weighing Li2CO3, MgO, and TiO2 in a molar ratio of 1:1:3, ball-milling and mixing, drying, calcining at 850-950°C for 4-6 hours, and then ball-milling and drying to obtain the Li2MgTi3O8 ceramic powder; The BaZn2Ti4O 11 The preparation method of ceramic powder comprises the following steps: weighing BaCO3, ZnO and TiO2 in a molar ratio of 1:2:4, mixing by ball milling, drying, calcining at 900-1000°C for 4-6 hours, and then ball milling and drying to obtain BaZn2Ti4O 11 Ceramic powder.

5. The preparation method according to claim 3, wherein: The high-temperature calcination in step S2 is performed at a temperature of 1100-1250° C. and for a time of 4-6 hours.

6. The preparation method according to claim 3, wherein: Step S3 includes one or a combination of the following conditions: An adhesive is added before granulation, and the adhesive is one of PVA, PVB or sodium polyacrylate; The compression molding pressure is 6~7Mpa; The high-temperature calcination step includes: first heating from room temperature to 550-650°C at a heating rate of 2°C / min, and keeping the temperature for 2 hours; then heating to 1280-1400°C at a heating rate of 5°C / min, and keeping the temperature for 4 hours.

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