CN1331807C - Low temperature sintered microwave dielectric ceramic with high dielectric constant and its prepn process - Google Patents

Abstract

The invention relates to a high dielectric constant low-temperature sintered microwave dielectric ceramic and a preparation method thereof. The raw materials Li ₂ CO ₃ , Nb ₂ O ₅ , and TiO ₂ are mixed in ethanol, dried and calcined, and V ₂ O ₅ and ZnO-B ₂ O ₃ -SiO ₂ (ZBS for short) glass made by sol-gel method, mixed, dried, pressed into small discs, and fired to obtain the material of the present invention. The characteristics of the present invention: use V ₂ O ₅ and ZBS to synergistically reduce the sintering temperature of the material, and adjust the frequency temperature coefficient of the material; the specific process improves the characteristics of the powder and slurry, and achieves a better co-firing match with the silver electrode ; Sintering at around 900°C has good microwave dielectric properties: ε=50~70; Q·f>4000GHz, frequency temperature coefficient τ _f =-10~+10ppm/°C; material process is stable and reproducible . The material of the invention is a very valuable low-temperature sintered microwave dielectric ceramic material, which can be applied to the design and production of multi-layer microwave frequency devices such as multi-layer band-pass filters, high-pass filters, low-pass filters, duplexers, antennas, and baluns. .

Description

A low-temperature sintered microwave dielectric ceramic with high dielectric constant and its preparation method

technical field

The invention relates to a low-temperature sintered microwave dielectric ceramic with high dielectric constant and a preparation method thereof, belonging to the technical field of material science.

Background technique

After more than 30 years, modern mobile communication has become increasingly popular all over the world, and is developing in the direction of miniaturization, high frequency, integration, high reliability and low cost. In order to meet the needs of portability and miniaturization of mobile communication terminals, the initial effort was to reduce the size of the resonant circuit. Searching for high dielectric constant microwave dielectric materials is a research hotspot, but the degree of miniaturization is limited. Advanced multilayer integrated circuit technology (MLIC) has made the miniaturization of devices develop rapidly. At present, companies such as TDK and MURATA use stacked co-firing technology to integrate several Ls and Cs together to produce stacked chip LC assemblies, such as low-pass filters, high-pass filters, band-pass filters, and notch waves. devices, delay lines, etc. The size of the band-pass filter produced by MURATA's multi-layer technology can be reduced to 2.0mm×1.25mm×1.0mm; recently launched the LDAG2 type laminated antenna specially used for Bluetooth high-frequency modules, the working frequency band is 0.8-2.4GHZ, The size is reduced to 9.5mm x 2.0mm x 2.0mm. It is under the premise of the miniaturization of microwave devices that the development of low-temperature sintered microwave materials that can be co-sintered with high-conductivity metals has become increasingly important. From the perspective of economy and environmental protection, the use of Ag(t A base metal such as _d =960°C) or Cu (t _d =1060°C) is ideal as an electrode material. Therefore, the research and development of low-temperature sintered microwave dielectric ceramics that can be co-fired with Ag or Cu or Ni have been put on the agenda.

At present, domestic and foreign scientific and technical personnel have carried out a lot of research work on low temperature, such as using low melting point sintering aids, wet chemical methods, reducing the fineness of raw materials and other methods to reduce the firing temperature of materials. Chen-Liang Huang et al used CuO flux to form CuO-Cu ₂ O-TiO ₂ (Cu ₃ TiO ₄ ) for 1% ZST ceramics doped with W(ZnO), which can be fired at 1220°C. is 5.12g/cm ³ , ε _r =38, Qf =5×10 ⁴ GHz; Jean and Lin used ZnO-B ₂ O ₃ -SiO ₂ and BCC (BaCO ₃ +CuO) as sintering aids to obtain ε _r = 35～38, Qf=2800～5000GHz. While studying low temperature, materials with lower sintering temperature, such as ZnTiO ₃ system, BiNbO ₄ system and (Pb, Ca)(Fe _1/2 Nb _1/2 )O ₃ system, have aroused people's interest. Wen-Cheng Tzou et al. used CuO, V ₂ O ₅ and compound addition of BiNbO ₄ to obtain dense ceramics at a low temperature of 875 ° C. In addition, La ³⁺ and Nb ³⁺ plasmas were used to replace part of Bi ³⁺ , and Ta ⁵⁺ was used to replace part of Nb ⁵⁺ , discussed the effect of substitution amount on lattice distortion, orthorhombic phase and triclinic phase transition process and dielectric properties; Jong-Yoon et al used Ca to replace Pb(Fe _1/2 Nb _1/2 )O ₃ to make it The ferroelectric phase of the material is transformed into a paraelectric phase, and a small amount of CuO-Bi ₂ O ₃ is added to reduce the sintering temperature of the material to 1000°C.

Most of the existing microwave dielectric ceramics have the problem of high sintering temperature. Although the sintering temperature of some materials is lowered to below 900°C, there are few practical low-temperature sintered microwave dielectric ceramic materials due to the large temperature coefficient of frequency, low quality factor, and interface reaction with silver electrodes, which hinders many Development of multilayer microwave devices.

Contents of the invention

The purpose of the present invention is to provide a high dielectric constant low-temperature sintered microwave dielectric ceramic material and its preparation method based on the miniaturization requirements of microwave devices for microwave dielectric ceramic materials. _Li2O -Nb with excellent microwave dielectric properties is selected _{The 2} O ₅ -TiO ₂ system uses V ₂ O ₅ and ZBS as sintering aids to reduce the sintering temperature while maintaining good microwave dielectric properties and can be co-fired with silver electrodes. This material is a promising material and has been put into industrial production.

A low-temperature sintered microwave dielectric material and a preparation method proposed by the present invention include the following:

①According to the following ratio for ingredients:

Li _(1+ab) Nb _(1-a-3b) Ti _(a+4b) O ₃ , where a=0.05～0.2; b=0.05～0.15

Based on the weight sum of _the required raw materials _Li2CO3 , _Nb2O5 and _TiO2 being 100%, the weight percentage _of the additive is:

V ₂ O ₅ : 1～5wt%

Zinc borosilicate glass (ZnO-B ₂ O ₃ -SiO ₂ , ZBS for short): 0-8 wt%.

② Weigh the raw materials Li ₂ CO ₃ , Nb ₂ O ₅ , TiO ₂ according to the above formula composition, according to the weight ratio of the mixed raw materials and ethanol as 1:1.5, add ethanol, and mix 16~ 24h, dry at 60-100°C, put it into a high-alumina crucible, and pre-fire at 800°C-900°C for 2-8h;

③After pre-burning, add 1~5wt% V ₂ O ₅ , 0~8wt% ZBS to the powder, according to the weight ratio of mixture and ethanol is 1:1.5, add ethanol, and mix 16 ~24h, dry at 60~100°C, add 5% PVA solution, press into small discs under a pressure of 4~10MPa, sinter at 850°C~950°C, and keep warm for 1~6h.

A method for preparing high dielectric constant low-temperature sintered microwave dielectric ceramics, comprising the following contents:

① Raw materials are prepared according to the following proportions:

Li _(1+ab) Nb _(1-a-3b) Ti _(a+4b) O ₃ , where a=0.15, b=0.075;

② Weigh the raw materials Li ₂ CO ₃ , Nb ₂ O ₅ , TiO ₂ according to the above formula composition, according to the weight ratio of the mixed raw materials and ethanol as 1:1.5, add ethanol, and mix in a rolling mill at a speed of 300r/min for 24h, 60～ Dry at 100°C, put it into a high-alumina crucible, and pre-fire at 850°C-900°C for 3-6 hours;

③After pre-burning, add 2wt% V ₂ O ₅ to the powder, according to the weight ratio of the mixture and ethanol is 1:1.5, add ethanol, mix in a rolling mill at a speed of 300r/min for 24 hours, dry at 60-100°C, add 5 %PVA solution, pressed into small discs under a pressure of 4-10MPa, sintered at 850°C-950°C, and kept for 1-6h.

A method for preparing high dielectric constant low-temperature sintered microwave dielectric ceramics, comprising the following contents:

① Raw materials are formulated according to the following ingredients:

Li _(1+ab) Nb _(1-a-3b) Ti _(a+4b) O ₃ , where a=0.15, b=0.1;

② Weigh the raw materials Li ₂ CO ₃ , Nb ₂ O ₅ , TiO ₂ according to the above formula composition, according to the weight ratio of the mixed raw materials and ethanol as 1:1.5, add ethanol, and mix in a rolling mill at a speed of 300r/min for 24h, 60～ Dry at 100°C, put it into a high-alumina crucible, and pre-fire at 850°C-900°C for 3-6 hours;

③After pre-burning, add 2wt% V ₂ O ₅ to the powder, according to the weight ratio of the mixture and ethanol is 1:1.5, add ethanol, mix in a rolling mill at a speed of 300r/min for 24 hours, dry at 60-100°C, add 5 %PVA solution, pressed into small discs under a pressure of 4-10MPa, sintered at 850°C-950°C, and kept for 1-6h.

The present invention composed of the above formula and process can obtain ε adjustable between 50～70, Q f>4000～6000GHz (resonant frequency f=2.0～3.0GHz), microwave dielectric ceramic material with adjustable frequency temperature coefficient , the performance has reached the level of similar low-temperature sintered microwave dielectric materials abroad, can replace imported materials, and promote the development process of multilayer microwave frequency devices in my country. The present invention has the following characteristics:

① Use V ₂ O ₅ and ZBS to reduce the sintering temperature synergistically, and comprehensively control the frequency temperature coefficient of the material;

②The specific process system improves the characteristics of the slurry and has a better co-firing match with the silver electrode;

③Sintering at around 900°C has good microwave dielectric properties: ε=50~70; Q.f>4000GHz, frequency temperature coefficient within -10~+10ppm/°C;

④ Higher dielectric constant reduces the design size of multilayer microwave devices and meets the purpose of device miniaturization; higher quality factor greatly reduces the insertion loss of microwave frequency devices;

⑤ The material process is stable and reproducible, and has been put into industrial production of multilayer microwave ceramic filters.

Detailed ways

The present invention will be further described below in conjunction with embodiment.

Table 1 is four ratio formulas of the present invention

serial number Component  Basic raw materials a, b (according to the amount of substance) Sintering aid (by weight percentage wt%) composition A b V ₂ O ₅ (c)   ZBS glass (d) 1 0.15 0.075 2 0 2 0.15 0.075 1 0 3 0.15 0.1 1 2 4 0.15 0.1 1 5

In the formula shown in Table 1, high-purity raw materials are required.

1. According to the above ratio formula, weigh LiCO ₃ , Nb ₂ O ₅ , TiO ₂ , according to the weight ratio of mixture and ethanol is 1:1.5, add ethanol, mix in rolling mill at 300r/min for 24h, dry, Put it into a corundum crucible, calcinate at 850°C for 4 hours, add 2wt% V ₂ O ₅ to the calcined material, and add ethanol according to the weight ratio of the mixture to ethanol at 1:1.5, and mix it in a rolling mill at a speed of 300r/min for 24 hours. Drying, ball milling to an average particle size of <1um, pressing under a pressure of 4MPa to form small discs with a diameter of 25mm and a thickness of 10-13mm, and sintering at 900°C for 4h to obtain the material of the present invention.

2. According to the above ratio formula, weigh LiCO ₃ , Nb ₂ O ₅ , TiO ₂ , according to the weight ratio of mixture and ethanol is 1:1.5, add ethanol, mix in rolling mill at 350r/min for 24h, dry, Put it into a corundum crucible, calcinate at 850°C for 4 hours, add 1wt% V ₂ O ₅ to the calcined material, and add ethanol according to the weight ratio of the mixture to ethanol at 1:1.5, and mix at a rolling mill at a speed of 350r/min for 24 hours. Drying, ball milling to an average particle size of <1um, pressing under a pressure of 4MPa to form small discs with a diameter of 25mm and a thickness of 10-13mm, and sintering at 895°C for 2 hours to obtain the material of the present invention.

3. According to the above ratio formula, weigh LiCO ₃ , Nb ₂ O ₅ , TiO ₂ , according to the weight ratio of mixture and ethanol is 1:1.5, add ethanol, mix in rolling mill at 300r/min for 18h, dry, Put it into a corundum crucible and calcinate at 850°C for 6 hours. Add 1wt% V ₂ O ₅ and 2wt% ZBS to the calcined material. According to the weight ratio of the mixture to ethanol is 1:1.5, add ethanol and roll at a speed of 300r/min. Mix for 18 hours, dry, ball mill until the average particle size is less than 1um, press under a pressure of 4MPa to form small discs with a diameter of 25mm and a thickness of 10-13mm, and sinter at 915°C for 2 hours to obtain the material of the present invention.

4. According to the above ratio formula, weigh LiCO ₃ , Nb ₂ O ₅ , TiO ₂ , according to the weight ratio of mixture and ethanol is 1:1.5, add ethanol, mix in rolling mill at 300r/min for 24h, dry, Put it into a corundum crucible, calcinate at 850°C for 4 hours, add 1wt% V ₂ O ₅ , 5wt% ZBS to the calcined material, and add ethanol according to the weight ratio of the mixture to ethanol at 1:1.5, and roll at a speed of 300r/min Mix for 24 hours, dry, ball mill until the average particle size is <1um, press under a pressure of 4MPa to form small discs with a diameter of 25mm and a thickness of 10-13mm, and sinter at 896°C for 4 hours to obtain the material of the present invention.

The dielectric properties of the discs pressed by the four formulations of the present invention are shown in the table below.

serial number f(GHz) ε Q f(GHz) τ _f (ppm/℃)/(25℃～85℃) 1 2.4368 66.31 4805 0.4 2 2.5472 65.54 4702 -18.9 3 2.7008 59.72 5304 31.3 4 2.6659 56.86 5070 3.0

Claims (4)

1. A low-temperature sintered microwave dielectric ceramic with high dielectric constant, characterized in that its formula consists of: Li _(1+ab) Nb _(1-a-3b) Ti _(a+4b) O ₃ , where a=0.05～0.2; b=0.05～0.15 Based on the weight sum of _the required raw materials _Li2CO3 , _Nb2O5 and _TiO2 being 100%, the weight percentage _of the additive is: V ₂ O ₅ : 1～5wt% Zinc borosilicate glass: 0-8wt%. 2. A method for preparing high dielectric constant low-temperature sintered microwave dielectric ceramics, characterized in that the preparation process comprises the following steps: ①According to the formula, the composition formula is Li _(1+ab) Nb _(1-a-3b) Ti _(a+4b) O ₃ , where a=0.05～0.2, b=0.05～0.15 Weigh raw materials Li ₂ CO ₃ , Nb ₂ O ₅ and TiO ₂ , according to the weight ratio of the mixed raw material and ethanol is 1:1.5, add ethanol, mix at a rolling mill at a speed of 200-400r/min for 16-24h, dry at 60-100°C, and put it into a high-alumina crucible Inside, pre-fire at 800℃～900℃ for 2～8h; ②After pre-burning, add 1~5wt% V ₂ O ₅ , 0~8wt% zinc borosilicate glass to the powder, according to the weight ratio of mixture and ethanol is 1:1.5, add ethanol, and the speed is 200~400r/min Roll mill and mix for 16-24 hours, dry at 60-100°C, add 5% PVA solution, press into small discs under a pressure of 4-10MPa, sinter at 850°C-950°C, and keep warm for 1-6h. 3. A method for preparing high dielectric constant low-temperature sintered microwave dielectric ceramics according to claim 2, characterized in that: ① Raw materials are prepared according to the following proportions: Li _(1+ab) Nb _(1-a-3b) Ti _(a+4b) O ₃ , where a=0.15, b=0.075; ② Weigh the raw materials Li ₂ CO ₃ , Nb ₂ O ₅ , TiO ₂ according to the above formula composition, according to the weight ratio of the mixed raw materials and ethanol as 1:1.5, add ethanol, and mix in a rolling mill at a speed of 300r/min for 24h, 60～ Dry at 100°C, put it into a high-alumina crucible, and pre-fire at 850°C-900°C for 3-6 hours; ③After pre-burning, add 2wt% V ₂ O ₅ to the powder, according to the weight ratio of the mixture and ethanol is 1:1.5, add ethanol, mix in a rolling mill at a speed of 300r/min for 24 hours, dry at 60-100°C, add 5 %PVA solution, pressed into small discs under a pressure of 4-10MPa, sintered at 850°C-950°C, and kept for 1-6h. 4. A method for preparing high dielectric constant low-temperature sintered microwave dielectric ceramics according to claim 2, characterized in that: ① Raw materials are formulated according to the following ingredients: Li _(1+ab) Nb _(1-a-3b) Ti _(a+4b) O ₃ , where a=0.15, b=0.1; ② Weigh the raw materials Li ₂ CO ₃ , Nb ₂ O ₅ , TiO ₂ according to the above formula composition, according to the weight ratio of the mixed raw materials and ethanol as 1:1.5, add ethanol, and mix in a rolling mill at a speed of 300r/min for 24h, 60～ Dry at 100°C, put it into a high-alumina crucible, and pre-fire at 850°C-900°C for 3-6 hours; ③After pre-burning, add 2wt% V ₂ O ₅ to the powder, according to the weight ratio of the mixture and ethanol is 1:1.5, add ethanol, mix in a rolling mill at a speed of 300r/min for 24 hours, dry at 60-100°C, add 5 %PVA solution, pressed into small discs under a pressure of 4-10MPa, sintered at 850°C-950°C, and kept for 1-6h.