CN103864424B - A kind of preparation method of microwave dielectric ceramic materials - Google Patents
A kind of preparation method of microwave dielectric ceramic materials Download PDFInfo
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- CN103864424B CN103864424B CN201210544200.4A CN201210544200A CN103864424B CN 103864424 B CN103864424 B CN 103864424B CN 201210544200 A CN201210544200 A CN 201210544200A CN 103864424 B CN103864424 B CN 103864424B
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Abstract
The invention discloses a kind of preparation method of microwave dielectric ceramic materials.Method comprises: nitrate of baryta, magnesium nitrate, niobium oxalate and citric acid are dissolved in respectively in the aqueous solution, forms mixing solutions; In mixing solutions, add ammonia soln and constantly stir, until form vitreosol; Vitreosol drying is obtained xerogel; Xerogel is carried out high-temperature calcination, obtains the precursor powder of pottery.On the basis of this powder body material, thus can utilize Microwave Sintering Techniques that this microwave dielectric nano-ceramic powder material sintering is obtained nano ceramics.By the way, the present invention can make to prepare in the process of microwave dielectric ceramic materials, reduces sintering temperature, improves the performance of this material simultaneously, effectively reduces industrial energy consumption and the production cost of this material system.
Description
Technical field
The present invention relates to stupalith field, particularly relate to a kind of preparation method of microwave dielectric ceramic materials.
Background technology
Microwave-medium ceramics is being applied in microwave frequency band (mainly ultra-high frequency UHF and ultra-high frequency SHF) circuit as dielectric material of growing up over nearly 30 years and completes the new function electron ceramic material of one or more functions, in the modern communicationses such as mobile communication, satellite communications, military radar, global positioning system (GPS), Bluetooth technology, WLAN (wireless local area network), be widely used as the components and parts such as resonator, wave filter, dielectric substrate, medium wave circuit, be the key foundation material of modern communication technology.
Barium magnesium niobium system pottery (Ba (Mg
1/3nb
2/3) O
3, BMN) and there is complex perovskite structure, be a kind of microwave-medium ceramics very high in X-band Q value, it is extremely important dielectric material in the microwave high-frequency fields such as satellite communication.But this ceramic post sintering is but very difficult, sintering temperature is usually more than 1300 DEG C.Because BMN ceramic post sintering is poor, seriously constrain scale operation and the application of this system.
Summary of the invention
The technical problem that the present invention mainly solves is to provide a kind of preparation method of microwave dielectric ceramic materials, can in the process preparing microwave dielectric ceramic materials, reduce sintering temperature, improve the performance of this material simultaneously, effectively reduce industrial energy consumption and the production cost of this material system.
For solving the problems of the technologies described above, the technical scheme that the present invention adopts is: the preparation method providing a kind of microwave dielectric ceramic materials, comprising: nitrate of baryta, magnesium nitrate, niobium oxalate and citric acid are dissolved in respectively in the aqueous solution, forms mixing solutions; In described mixing solutions, add ammonia soln and constantly stir, until form vitreosol; Described vitreosol drying is obtained xerogel;
Described xerogel is carried out high-temperature calcination, obtains the precursor powder of pottery.
Wherein, the described ammonia soln that adds in mixing solutions also constantly stirs, and the step forming vitreosol comprises: at 60-80 DEG C, slowly ammoniacal liquor is added in described mixing solutions, and constantly stir, until the pH of mixing solutions reaches between 5-8, form vitreosol.
Wherein, described xerogel is carried out high-temperature calcination, the step obtaining the precursor powder of pottery comprises: xerogel is calcined 1-2 hour at 600-800 DEG C, obtains the precursor powder of pottery.
Wherein, described in obtain pottery precursor powder step after, also comprise: in the precursor powder of described pottery, add caking agent, fluidizer and organic solution, by granulation for powders, the precursor powder of described pottery made powder granule.
Wherein, the described precursor powder by pottery also comprises after making the step of powder granule: the blank described powder granule being made desired shape.
Wherein, described powder granule is made the step of the blank of desired shape after, also comprise: described blank is obtained microwave-medium ceramics through microwave sintering.
Wherein, described the step that blank obtains microwave-medium ceramics through microwave sintering to be comprised: described blank is carried out in retort furnace binder removal and just burn, temperature is 600-800 DEG C, and soaking time is 1-2 hour, and temperature rise rate is 0.5-1 DEG C/min; Sintered in microwave agglomerating furnace by described blank after just burning through binder removal, microwave frequency is 2.45GHz, and power is 1.5-3.0KW, and sintering temperature is 900-1200 DEG C, and sintering time is 1-2 hour.
Wherein, described nitrate of baryta, magnesium nitrate, niobium oxalate feed intake according to mol ratio 3:0.8 ~ 1.2:1.8 ~ 2.2, and total mol ratio of described citric acid and metal-salt is 1.5 ~ 2.0:1, and wherein, the purity of described nitrate of baryta, magnesium nitrate, niobium oxalate is all more than 99%.
Wherein, described nitrate of baryta, magnesium nitrate, niobium oxalate feed intake according to the mol ratio of chemical formula Ba (Mg1/3Nb2/3) O3-xMO, M represents at least one of 2/3La, 2/3B, Cu, the at least one of lanthanum nitrate, boric acid and cupric nitrate is added to the described aqueous solution according to the amount of mol ratio x=0.006-0.06, total mol ratio of described citric acid and the described all metal-salts added is 1.5 ~ 2.0:1, wherein, the purity of described nitrate of baryta, magnesium nitrate, niobium oxalate, lanthanum nitrate, boric acid and cupric nitrate is all more than 99%.
Wherein, described step vitreosol drying being obtained xerogel comprises: vitreosol drying in 120 DEG C of baking ovens is obtained xerogel.
The invention has the beneficial effects as follows: the situation being different from prior art, the present invention with nitrate of baryta, magnesium nitrate, niobium oxalate and citric acid for raw material, adopt the mode of solution method obtain atom level or only at least more than molecular level have high microscopic uniformity vitreosol, obtained the microwave dielectric nano-ceramic powder material of chemical composition and even particle size distribution by drying and calcining.On the basis of this powder body material, thus can utilize Microwave Sintering Techniques that this microwave dielectric nano-ceramic powder material sintering is obtained nano ceramics.By the method, the sintering temperature prepared in ceramic process is reduced greatly, improve again the quality factor of stupalith simultaneously, effectively reduce industrial energy consumption and the production cost of stupalith system.
Accompanying drawing explanation
Fig. 1 is the schema of preparation method's embodiment of microwave dielectric ceramic materials of the present invention;
Fig. 2 is the schema of another embodiment of preparation method of microwave dielectric ceramic materials of the present invention;
Fig. 3 is the XRD figure spectrum of the ceramic forerunner powder that embodiment of the present invention four prepares;
Fig. 4 is the SEM figure of the ceramic forerunner powder that embodiment of the present invention four prepares;
Fig. 5 is the XRD figure spectrum of the microwave-medium ceramics that embodiment of the present invention four prepares;
Fig. 6 is the SEM figure of the microwave-medium ceramics that embodiment of the present invention four prepares.
Embodiment
Embodiment one
Refer to Fig. 1, preparation method's embodiment of microwave dielectric ceramic materials of the present invention, comprises the following steps:
Step S101: nitrate of baryta, magnesium nitrate, niobium oxalate and citric acid are dissolved in respectively in the aqueous solution, forms mixing solutions;
With nitrate of baryta Ba (NO
3)
2, magnesium nitrate Mg (NO
3)
26H
2o, niobium oxalate C
10h
5nbO
20with citric acid C
6h
8o
7h
2o is starting raw material, is dissolved in deionized water solution.Wherein, can according to Ba (NO
3)
2: Mg (NO
3)
26H
2o:C
10h
5nbO
20the molar ratio of=3:0.8 ~ 1.2:1.8 ~ 2.2 feeds intake, and citric acid is 1.5 ~ 2.0:1 with the ratio of the integral molar quantity of metal-salt.Wherein, the purity of nitrate of baryta, magnesium nitrate and niobium oxalate is all more than 99%.All original raw materials are all dropped in the aqueous solution, carries out stirring all raw materials are all dissolved, form mixing solutions.
In another embodiment, in above-mentioned formation mixing solutions process, a small amount of properties-correcting agent and sintering aid can also be added.Wherein, can with lanthanum nitrate La (NO
3)
36H
2o adds as properties-correcting agent, with boric acid H
3bO
3and cupric nitrate Cu (NO
3)
26H
2at least one of O adds as sintering aid.
Step S102: add ammoniacal liquor and constantly stir in mixing solutions, until form vitreosol;
By slowly adding ammoniacal liquor in the solution and constantly stirring, until form transparent colloidal sol.Usually, be heated to 60-80 DEG C by aobvious for mixing solutions, then add ammoniacal liquor, control the pH of mixing solutions between 5 ~ 8, namely stop adding ammoniacal liquor, stir and make mixing solutions form vitreosol.
Because original raw material mixes in the form of a solution, atom level can be obtained or be at least the vitreosol that more than molecular level has high microscopic uniformity.
Step S103: vitreosol drying is obtained xerogel;
By dry for vitreosol to obtain xerogel.Such as can by vitreosol as dry in baking oven.Wherein, dry temperature should control at 120 DEG C.
Step S104: precursor powder xerogel high-temperature calcination being obtained pottery;
Xerogel is obtained in retort furnace the precursor powder of pottery through high-temperature calcination.The temperature of usual control calcining is 600 ~ 800 DEG C, and soaking time is 1 ~ 2 hour.
By above-mentioned embodiment, can prepare the precursor powder of microwave-medium ceramics, powder is the nanometer powder of 50 ~ 500nm.
Embodiment two
Refer to Fig. 2, another embodiment of the preparation method of microwave dielectric ceramic materials of the present invention, comprises the following steps:
Step S201: nitrate of baryta, magnesium nitrate, niobium oxalate and citric acid are dissolved in respectively in the aqueous solution, forms mixing solutions;
With nitrate of baryta Ba (NO
3)
2, magnesium nitrate Mg (NO
3)
26H
2o, niobium oxalate C
10h
5nbO
20with citric acid C
6h
8o
7h
2o is starting raw material, is dissolved in the aqueous solution.Wherein, can according to Ba (NO
3)
2: Mg (NO
3)
26H
2o:C
10h
5nbO
20the molar ratio of=3:1 ~ 1.2:2 ~ 2.2 feeds intake, and citric acid is 1.5 ~ 2.0:1 with the ratio of the integral molar quantity of metal-salt.Wherein, the purity of nitrate of baryta, magnesium nitrate and niobium oxalate is all more than 99%.All original raw materials are all dropped in the aqueous solution, carries out stirring all raw materials are all dissolved, form mixing solutions.
In another embodiment, in above-mentioned formation mixing solutions process, a small amount of properties-correcting agent and sintering aid can also be added.Wherein, can with lanthanum nitrate La (NO
3)
36H
2o adds as properties-correcting agent, with boric acid H
3bO
3and cupric nitrate Cu (NO
3)
26H
2at least one of O adds as sintering aid.
Step S202: add ammoniacal liquor and constantly stir in mixing solutions, until form vitreosol;
By slowly adding ammoniacal liquor in the solution and constantly stirring, until form transparent colloidal sol.Usually, be heated to 60-80 DEG C by aobvious for mixing solutions, then add ammoniacal liquor, control the pH of mixing solutions between 5 ~ 8, namely stop adding ammoniacal liquor, stir and make mixing solutions form vitreosol.
Because original raw material mixes in the form of a solution, atom level can be obtained or be at least the vitreosol that more than molecular level has high microscopic uniformity.
Step S203: vitreosol drying is obtained xerogel;
By dry for vitreosol to obtain xerogel.Such as can by vitreosol as dry in baking oven.Wherein, dry temperature should control at 120 DEG C.
Step S204: precursor powder xerogel high-temperature calcination being obtained pottery;
Xerogel is obtained in retort furnace the precursor powder of pottery through high-temperature calcination.The temperature of usual control calcining is 600 ~ 800 DEG C, and soaking time is 1 ~ 2 hour.
Step S205: add caking agent, fluidizer and organic solution in the precursor powder of pottery, makes powder granule by granulation for powders by the precursor powder of pottery;
On the basis of the precursor powder of the above-mentioned pottery prepared, granulation for powders technique can be carried out further, namely in the precursor powder of pottery, caking agent, fluidizer and organic solvent is added, uniformly mix, adopt the mode of conventional granulation for powders such as mist projection granulating that powder is made powder granule.
Step S206: blank powder granule being made desired shape;
By namely powder granule compression moulding being obtained the pressed compact of desired shape.Pressed compact carries out two-sided compression moulding by pressing machine in filler mode manually or automatically, or it is shaping to carry out a shot by shot forming technique.
Step S207: blank is obtained microwave-medium ceramics through microwave sintering;
Microwave sintering refers to and utilizes the dielectric loss of stupalith in microwave electromagnetic field to make material monolithic be heated to sintering temperature and realize sintering and densification.Microwave is a kind of frequency electromagnetic waves, and its range of frequency is 0.5 ~ 300GHz; In microwave sintering, frequency of utilization is mainly 2.45GHz.
Under microwave electromagnetic field action, stupalith can produce a series of dielectric polarization, as electronic polarization, atomic polarization, dipole pilot polarization and interfacial polarization etc.The microcosmic particle kind of participating in polarization is different, and the time cycle of setting up or eliminating polarization is also different.
Because the frequency of microwave electromagnetic field is very high, make the dielectric polarization process of material internal cannot follow the change of external electric field, polarized arrest P always lags behind electric field E, cause producing the electric current with electric field homophase, thus the dissipation of constituent material inside, in microwave region, the medium of the absorption current constituent material of mainly dipole polarization and interfacial polarization generation dissipates, and namely the interaction of material and microwave causes material for absorbing microwave energy and heated.
The principle of microwave sintering and conventional sintering process have the difference of essence: during normal sintering, heat is by showing to spread inwards by medium, microwave sintering then make use of the body heat characteristic of microwave, namely the micro-wave energy of absorbed is converted into kinetic energy and the potential energy of material internal molecule, make material monolithic homogeneous heating simultaneously, therefore its heating and sintering velocity are quickly; Due to simultaneously thermally equivalent inside and outside material, make the thermograde of sample inside very little, thus material internal thermal stresses can be made to reduce to minimum, this is highly beneficial for the medium ceramic material preparing high densification.
Such as to TiO
2the microwave sintering of nano ceramics, can make TiO at 950 DEG C
2reach the density of theoretical density 98%.For stoping the grain growth in sintering process, the method that rapid microwave sinters can be adopted.Such as, containing yttrium ZrO
2the sintering of nano powder (10 ~ 20nm) base substrate, if heat up, rate of temperature fall remains on 500 DEG C/min, 2min is incubated at 1200 DEG C, more than 95% of sintered density accessibility theory density, whole sintering process only needs 7min, and the grain-size in sintered compact can be controlled in below 120nm.
In embodiment of the present invention, the mode of microwave sintering is adopted to prepare nano ceramics.Before microwave sintering, binder removal can be carried out by retort furnace and just burn, the organic constituent in green compact is burnt, avoid the cracking causing goods in microwave sintering process, the defects such as warpage.The temperature range that binder removal just burns can be controlled in 600 ~ 800 DEG C, and temperature rise rate is 0.5 ~ 1 DEG C/min, is incubated 1 ~ 2 hour after arriving temperature.
During microwave sintering, control microwave frequency is 2.45GHz, and power is 1.5-3.0KW, and sintering temperature is 900 ~ 1200 DEG C, and sintering time is 1 ~ 2 hour.
By the way, can be implemented in less than 1200 DEG C densifications and burn till barium magnesium niobium microwave-medium nano ceramics, by the nano ceramics that embodiments of the present invention prepare, there is the specific inductivity of 32.1 ~ 35.2 through test, the quality factor (i.e. Q × f) of 90000 ~ 110000GHz, near-zero resonance frequency temperature coefficient τ
f(-10 ~ 10ppm/ DEG C).
Embodiment three
Present embodiment adopts Ba (Mg
1/3nb
2/3) O
3-0.06La
2/3o chemical constitution percentage, with the nitrate of baryta of purity 99%, magnesium nitrate, niobium oxalate, lanthanum nitrate for starting raw material, and is realized by following processing step.
1) with the nitrate of baryta of purity 99% (Ba (NO
3)
2), magnesium nitrate (Mg (NO
3)
26H
2o), niobium oxalate (C
10h
5nbO
20), lanthanum nitrate (La (NO
3)
36H
2and citric acid (C O)
6h
8o
7h
2o) be starting raw material.Be dissolved in a certain amount of deionized water by the mol ratio of above-mentioned chemical constitution by nitrate of baryta, magnesium nitrate, niobium oxalate and citric acid, form solution, total mol ratio of the citric acid wherein added and metal ion nitrate is 1.5:1.Then, lanthanum nitrate is added by above-mentioned chemical constitution mol ratio, dissolve and form mixing solutions;
2) ammoniacal liquor is slowly added in the mixing solutions that step 1 prepares, until pH value reaches 5.Mixing solutions is first heated to 60 DEG C, then adds ammoniacal liquor, and Keep agitation controls the pH of mixing solutions 5, forms vitreosol;
3) baking oven colloidal sol that step 2 is prepared being placed in 120 DEG C is dried, until form xerogel;
4) xerogel step 3 obtained carries out pre-burning (calcining temperature 780 DEG C, burn-in time 1 hour), obtains Ba (Mg
1/3nb
2/3) O
3the precursor powder (50 ~ 500 nanometer) of base media ceramic;
5) Ba (Mg step 4 synthesized
1/3nb
2/3) O
3base ceramic forerunner powder adds caking agent, fluidizer and organic solvent etc. and uniformly mixes, and utilizes traditional technology to carry out the compression moulding of granulation for powders and blank;
6) shaping blank in step 5 is carried out binder removal at traditional retort furnace just to burn, then at microwave sintering kiln roasting Ba (Mg
1/3nb
2/3) O
3base microwave dielectric ceramics.Wherein, it is 780 DEG C that the temperature that binder removal just burns controls, and is incubated 1 hour.Microwave frequency is 2.45GHz, power is 1.5KW, sintering temperature is 1150 DEG C, the integral sintered time is 1 hour.
The relative permittivity ε of microwave-medium ceramics that obtains of present embodiment after tested
rbe 33.7, quality factor (Q × f) value is 94300GHz, temperature coefficient of resonance frequency τ
ffor 8ppm/ DEG C.
Embodiment four
Present embodiment adopts Ba (Mg
1/3nb
2/3) O
3-0.06La
2/3o-0.006B
2/3o chemical constitution percentage, with the nitrate of baryta of purity 99%, magnesium nitrate, niobium oxalate, lanthanum nitrate and boric acid for starting raw material, and is realized by following processing step:
1) with the nitrate of baryta of purity 99% (Ba (NO
3)
2), magnesium nitrate (Mg (NO
3)
26H
2o), niobium oxalate (C
10h
5nbO
20), lanthanum nitrate (La (NO
3)
36H
2o), boric acid (H
3bO
3) and citric acid (C
6h
8o
7h
2o) be starting raw material.Be dissolved in a certain amount of deionized water by the mol ratio of above-mentioned chemical constitution by nitrate of baryta, magnesium nitrate, niobium oxalate and citric acid, form solution, total mol ratio of the citric acid wherein added and metal ion nitrate is 1.6:1.Then, nitric acid is calumniated and boric acid add by the mol ratio of above-mentioned chemical constitution, dissolve formed mixing solutions;
2) ammoniacal liquor is slowly added in the mixing solutions that step 1 prepares, at 80 DEG C, ammoniacal liquor is added above-mentioned mixing solutions and Keep agitation, until pH value reaches 7, form vitreosol;
3) baking oven colloidal sol that step 2 is prepared being placed in 120 DEG C is dried, until form xerogel;
4) xerogel step 3 obtained carries out pre-burning (calcining temperature 650 DEG C, burn-in time 1 hour), obtains Ba (Mg
1/3nb
2/3) O
3the precursor powder (50 ~ 500 nanometer) of base media ceramic;
5) Ba (Mg step 4 synthesized
1/3nb
2/3) O
3base ceramic forerunner powder adds caking agent, fluidizer and organic solvent etc. and uniformly mixes, and utilizes traditional technology to carry out the compression moulding of granulation for powders and blank;
6) shaping blank in step 5 is carried out binder removal at traditional retort furnace just to burn, then at microwave sintering kiln roasting Ba (Mg
1/3nb
2/3) O
3base microwave dielectric ceramics.Wherein, the temperature that binder removal just burns is 620 DEG C, and soaking time is 2 hours.Microwave frequency is 2.45GHz, power is 2.5KW, sintering temperature is 1050 DEG C, the integral sintered time is 1 hour.
The relative permittivity ε of microwave-medium ceramics for preparing of this embodiment after tested
rbe 35.2, quality factor (Q × f) value is 106900GHz, temperature coefficient of resonance frequency τ
ffor 3ppm/ DEG C.
The XRD figure spectrum of the precursor powder of the pottery prepared in present embodiment can consult Fig. 3, as seen from the figure, when calcining temperature is 650 DEG C, can obtain the BMN ceramic powder being bordering on pure phase.In figure, all diffraction peak intensities are moderate, and diffraction peak has obvious broadening phenomenon, and illustrate that the crystallinity of BMN ceramic powder is better, powder granule is small-sized, has good sintering activity.The SEM figure of precursor powder can consult Fig. 4, as seen from the figure, nano-powder presents good island pattern, although there is certain gathering at microcell in nano-powder, this is mainly because the specific surface area that nano-powder self is larger causes, but see that the island nano-powder that microcell is assembled is dispersed on the whole, show that nano-powder has good sintering activity.The mean diameter of nano-powder is 50nm, and particle shape is close to spherical.
The XRD figure spectrum of the microwave-medium ceramics prepared in present embodiment can consult Fig. 5, as seen from the figure, all diffraction peaks can both index change into the BMN(JCPDSfileno.17-0173 of hexagonal structure).In XRD figure spectrum, any assorted peak do not detected, interpret sample has high purity.What the asterisk (*) in figure represented is BMN pottery superstructure diffraction peak, illustrates that BMN pottery has good cation ordering.The SEM figure of microwave-medium ceramics can consult Fig. 6, and as seen from the figure, BMN pottery microstructure is even, and without the abnormal growth phenomenon of crystal grain, average grain size is 400nm.
Embodiment five
Present embodiment adopts Ba (Mg
1/3nb
2/3) O
3-0.06La
2/3o-0.06CuO-0.006B
2/3o chemical constitution percentage, with the nitrate of baryta of purity 99%, magnesium nitrate, niobium oxalate, lanthanum nitrate, boric acid and cupric nitrate for starting raw material, and is realized by following processing step:
1) with the nitrate of baryta of purity 99% (Ba (NO
3)
2), magnesium nitrate (Mg (NO
3)
26H
2o), niobium oxalate (C
10h
5nbO
20), lanthanum nitrate (La (NO
3)
36H
2o), cupric nitrate (Cu (NO
3)
26H
2and citric acid (C O)
6h
8o
7h
2o) be starting raw material.Be dissolved in a certain amount of deionized water by the mol ratio of above-mentioned chemical constitution by nitrate of baryta, magnesium nitrate, niobium oxalate and citric acid, form solution, total mol ratio of the citric acid wherein added and metal ion nitrate is 2:1.Then, lanthanum nitrate and cupric nitrate are added by the mol ratio of above-mentioned chemical constitution, dissolve and form mixing solutions;
2) ammoniacal liquor is slowly added in the mixing solutions that step 1 prepares, until pH value reaches 7, at 70 DEG C, ammoniacal liquor is slowly added above-mentioned mixing solutions and Keep agitation, form vitreosol;
3) baking oven colloidal sol that step 2 is prepared being placed in 120 DEG C is dried, until form xerogel;
4) xerogel step 3 obtained carries out pre-burning (calcining temperature 710 DEG C, burn-in time 2 hours), obtains Ba (Mg
1/3nb
2/3) O
3the precursor powder (50 ~ 500 nanometer) of base media ceramic;
5) Ba (Mg step 4 synthesized
1/3nb
2/3) O
3base ceramic forerunner powder adds caking agent, fluidizer and organic solvent etc. and uniformly mixes, and utilizes traditional technology to carry out the compression moulding of granulation for powders and blank;
6) shaping blank in step 5 is carried out binder removal at traditional retort furnace just to burn, then at microwave sintering kiln roasting Ba (Mg
1/3nb
2/3) O
3base microwave dielectric ceramics.Wherein, the temperature that binder removal just burns is 730 DEG C, and soaking time is 1 hour.Microwave frequency is 2.45GHz, power is 1.5KW, sintering temperature is 900 DEG C, the integral sintered time is 2 hours.
7) the relative permittivity ε of this microwave-medium ceramics after tested
rbe 32.5, quality factor (Q × f) value is 85700GHz, temperature coefficient of resonance frequency τ
ffor-5ppm/ DEG C.
Embodiment six
Present embodiment Raw nitrate of baryta, magnesium nitrate and niobium oxalate, according to mol ratio 3:1.2:2.2, with the nitrate of baryta of purity 99%, magnesium nitrate, niobium oxalate for starting raw material, and are realized by following processing step:
1) with the nitrate of baryta of purity 99% (Ba (NO
3)
2), magnesium nitrate (Mg (NO
3)
26H
2o), niobium oxalate (C
10h
5nbO
20), citric acid (C
6h
8o
7h
2o) be starting raw material.Be dissolved in a certain amount of deionized water by nitrate of baryta, magnesium nitrate, niobium oxalate and citric acid according to the above ratio, form mixing solutions, total mol ratio of the citric acid wherein added and metal ion nitrate is 1.6:1.
2) ammoniacal liquor is slowly added in the mixing solutions that step 1 prepares, at 80 DEG C, ammoniacal liquor is slowly added above-mentioned mixing solutions and Keep agitation, until pH value reaches 6, form vitreosol;
3) baking oven colloidal sol that step 2 is prepared being placed in 120 DEG C is dried, until form xerogel;
4) xerogel step 3 obtained carries out pre-burning (calcining temperature 730 DEG C, burn-in time 2 hours), obtains the precursor powder (50 ~ 500 nanometer) of barium magnesium niobium microwave-medium ceramics;
5) ceramic forerunner powder step 4 synthesized adds caking agent, fluidizer and organic solvent etc. and uniformly mixes, and utilizes traditional technology to carry out the compression moulding of granulation for powders and blank;
6) shaping blank in step 5 is carried out binder removal at traditional retort furnace just to burn, then at microwave sintering kiln roasting barium magnesium niobium microwave-medium ceramics.Wherein, the temperature that binder removal just burns is 800 DEG C, and soaking time is 1 hour.Microwave frequency is 2.45GHz, power is 1.7KW, sintering temperature is 1100 DEG C, the integral sintered time is 2 hours.
7) the relative permittivity ε of this microwave-medium ceramics after tested
rbe 34.2, quality factor (Q × f) value is 100200GHz, temperature coefficient of resonance frequency τ
ffor 7ppm/ DEG C.
Embodiment seven
Present embodiment raw material nitrate of baryta, magnesium nitrate and niobium oxalate, according to mol ratio 3:1.1:2.1, with the nitrate of baryta of purity 99%, magnesium nitrate, niobium oxalate for starting raw material, and are realized by following processing step:
1) with the nitrate of baryta of purity 99% (Ba (NO
3)
2), magnesium nitrate (Mg (NO
3)
26H
2o), niobium oxalate (C
10h
5nbO
20), citric acid (C
6h
8o
7h
2o) be starting raw material.Be dissolved in a certain amount of deionized water by nitrate of baryta, magnesium nitrate, niobium oxalate and citric acid according to the above ratio, form mixing solutions, total mol ratio of the citric acid wherein added and metal ion nitrate is 1.55:1.
2) ammoniacal liquor is slowly added in the mixing solutions that step 1 prepares, at 70 DEG C, ammoniacal liquor is added above-mentioned mixing solutions and Keep agitation, until pH value reaches 8, form vitreosol;
3) baking oven colloidal sol that step 2 is prepared being placed in 120 DEG C is dried, until form xerogel;
4) xerogel step 3 obtained carries out pre-burning (calcining temperature 600 DEG C, burn-in time 2 hours), obtains the precursor powder (50 ~ 500 nanometer) of barium magnesium niobium microwave-medium ceramics;
5) ceramic forerunner powder step 4 synthesized adds caking agent, fluidizer and organic solvent etc. and uniformly mixes, and utilizes traditional technology to carry out the compression moulding of granulation for powders and blank;
6) shaping blank in step 5 is carried out binder removal at traditional retort furnace just to burn, then at microwave sintering kiln roasting barium magnesium niobium microwave-medium ceramics.Wherein, the temperature that binder removal just burns is 700 DEG C, and soaking time is 2 hours.Microwave frequency is 2.45GHz, power is 3.0KW, sintering temperature is 1170 DEG C, the integral sintered time is 1 hour.
The relative permittivity ε of this microwave-medium ceramics after tested
rbe 32.8, quality factor (Q × f) value is 95600GHz, temperature coefficient of resonance frequency τ
ffor 7ppm/ DEG C.
Embodiment eight
Present embodiment raw material nitrate of baryta, magnesium nitrate and niobium oxalate, according to mol ratio 3:0.8:1.8, with the nitrate of baryta of purity 99%, magnesium nitrate, niobium oxalate for starting raw material, and are realized by following processing step:
1) with the nitrate of baryta of purity 99% (Ba (NO
3)
2), magnesium nitrate (Mg (NO
3)
26H
2o), niobium oxalate (C
10h
5nbO
20), citric acid (C
6h
8o
7h
2o) be starting raw material.Be dissolved in a certain amount of deionized water by nitrate of baryta, magnesium nitrate, niobium oxalate and citric acid according to the above ratio, form mixing solutions, total mol ratio of the citric acid wherein added and metal ion nitrate is 1.7:1.
2) ammoniacal liquor is slowly added in the mixing solutions that step 1 prepares, at 80 DEG C, ammoniacal liquor is added above-mentioned mixing solutions and Keep agitation, until pH value reaches 5, form vitreosol;
3) baking oven colloidal sol that step 2 is prepared being placed in 120 DEG C is dried, until form xerogel;
4) xerogel step 3 obtained carries out pre-burning (calcining temperature 750 DEG C, burn-in time 1 hour), obtains the precursor powder (50 ~ 500 nanometer) of barium magnesium niobium microwave-medium ceramics;
5) ceramic forerunner powder step 4 synthesized adds caking agent, fluidizer and organic solvent etc. and uniformly mixes, and utilizes traditional technology to carry out the compression moulding of granulation for powders and blank;
6) shaping blank in step 5 is carried out binder removal at traditional retort furnace just to burn, then at microwave sintering kiln roasting barium magnesium niobium microwave-medium ceramics.Wherein, the temperature that binder removal just burns is 780 DEG C, and soaking time is 1 hour.Microwave frequency is 2.45GHz, power is 2.0KW, sintering temperature is 1200 DEG C, the integral sintered time is 2 hours.
The relative permittivity ε of this microwave-medium ceramics after tested
rbe 34.8, quality factor (Q × f) value is 105600GHz, temperature coefficient of resonance frequency τ
ffor 4ppm/ DEG C.
By the elaboration of above-mentioned embodiment, be different from the situation of prior art, the present invention with nitrate of baryta, magnesium nitrate, niobium oxalate and citric acid for raw material, adopt the mode of solution method obtain atom level or only at least more than molecular level have high microscopic uniformity vitreosol, obtained the microwave dielectric nano-ceramic powder material of chemical composition and even particle size distribution by drying and calcining.On the basis of this powder body material, thus can utilize Microwave Sintering Techniques that this microwave dielectric nano-ceramic powder material sintering is obtained nano ceramics.By the method, the sintering temperature prepared in ceramic process is reduced greatly, improve again the quality factor of stupalith simultaneously, effectively reduce industrial energy consumption and the production cost of stupalith system.
The foregoing is only embodiments of the present invention; not thereby the scope of the claims of the present invention is limited; every utilize specification sheets of the present invention and accompanying drawing content to do equivalent structure or equivalent flow process conversion; or be directly or indirectly used in other relevant technical fields, be all in like manner included in scope of patent protection of the present invention.
Claims (4)
1. a preparation method for microwave dielectric ceramic materials, is characterized in that, comprising:
Nitrate of baryta, magnesium nitrate, niobium oxalate and citric acid are dissolved in the aqueous solution respectively, form mixing solutions;
At 60-80 DEG C, in described mixing solutions, slowly add ammoniacal liquor, and constantly stir, until the pH of mixing solutions reaches between 5-8, form vitreosol;
Described vitreosol drying is obtained xerogel;
Xerogel is calcined 1-2 hour at 600-800 DEG C, and obtain the precursor powder of pottery, powder is the nanometer powder of 50 ~ 500nm;
In the precursor powder of described pottery, add caking agent, fluidizer and organic solution, by granulation for powders, the precursor powder of described pottery is made powder granule;
Described powder granule is made the blank of desired shape;
Described blank is carried out in retort furnace binder removal just to burn, temperature is 600-800 DEG C, and soaking time is 1-2 hour, and temperature rise rate is 0.5-1 DEG C/min;
Sintered in microwave agglomerating furnace by described blank after just burning through binder removal and obtain microwave-medium ceramics, microwave frequency is 2.45GHz, and power is 1.5-3.0KW, and sintering temperature is 900-1200 DEG C, and sintering time is 1-2 hour.
2. method according to claim 1, it is characterized in that, described nitrate of baryta, magnesium nitrate, niobium oxalate feed intake according to mol ratio 3:0.8 ~ 1.2:1.8 ~ 2.2, total mol ratio of described citric acid and metal-salt is 1.5 ~ 2.0:1, wherein, the purity of described nitrate of baryta, magnesium nitrate, niobium oxalate is all more than 99%.
3. method according to claim 1, is characterized in that, described nitrate of baryta, magnesium nitrate, niobium oxalate are according to chemical formula Ba (Mg
1/3nb
2/3) O
3the mol ratio of-xMO feeds intake, M represents at least one of 2/3La, 2/3B, Cu, the at least one of lanthanum nitrate, boric acid and cupric nitrate is added to the described aqueous solution according to the amount of mol ratio x=0.006-0.06, total mol ratio of described citric acid and the described all metal-salts added is 1.5 ~ 2.0:1, wherein, the purity of described nitrate of baryta, magnesium nitrate, niobium oxalate, lanthanum nitrate, boric acid and cupric nitrate is all more than 99%.
4. method according to claim 1, is characterized in that, described step vitreosol drying being obtained xerogel comprises: vitreosol drying in 120 DEG C of baking ovens is obtained xerogel.
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| 合成Ba(Mg1/3Nb2/3)O3纳米粉末的溶胶凝胶工艺与电子结构表征方法;徐利华等;《稀有金属材料与工程》;20080531;第37卷(第增刊2期);273－276 * |
| 微波介质陶瓷制备技术研究进展;郑勇等;《材料导报》;20041130;第18卷(第11期);73－76 * |
| 烧结制度对Ba(Mg1/3Nb2/3)O3陶瓷品质因子的影响;田中青等;《武汉理工大学学报》;20050630;第27卷(第6期);5－7 * |
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