CN101734907B - Transition element doped barium-strontium titanate based composite ceramic and preparation method thereof - Google Patents

Transition element doped barium-strontium titanate based composite ceramic and preparation method thereof Download PDF

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CN101734907B
CN101734907B CN 200910242480 CN200910242480A CN101734907B CN 101734907 B CN101734907 B CN 101734907B CN 200910242480 CN200910242480 CN 200910242480 CN 200910242480 A CN200910242480 A CN 200910242480A CN 101734907 B CN101734907 B CN 101734907B
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strontium titanate
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董桂霞
崔建东
杨志民
宋占永
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GRIMN Engineering Technology Research Institute Co Ltd
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Beijing General Research Institute for Non Ferrous Metals
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Abstract

The invention relates to a transition element doped barium-strontium titanate based composite ceramic, which comprises 40 weight percent of xM-Ba0.6Sr0.4TiO3 and 60 weight percent of MgO, wherein M is a transition metal, and x is the molar ratio of the transition metal M to Ba0.6Sr0.4TiO3 and ranges from 0.25 to 1.25 percent. Because of the doping of the transition element, the pressure control adjustable rate of the M-Ba0.6Sr0.4TiO3/MgO composite ceramic is improved, the microwave dielectric loss is greatly reduced, and meanwhile the breakdown field strengths of ceramic blocks are more than 28 kV/mm and can meet the using requirements of microwave dielectric materials.

Description

Transition element doped barium-strontium titanate based composite ceramic and preparation method thereof
Technical field
The present invention relates to a kind of transition element doped barium-strontium titanate based composite ceramic and preparation method thereof, particularly a kind of transition element doped low damage, barium-strontium titanate based composite ceramic of the voltage-controlled adjustability of high microwave and preparation method thereof, this material is specially adapted to the phased array phase shifter, adjustable filter, retarding line, vibrator, the microwave devices such as syntonizer.
Background technology
Phased array radar is that a kind of novel active electricity is swept the array multi-function array radar.It not only has the function of traditional radar, and has other radio-frequency enabled.The most important characteristics that active electricity is swept array are can be directly to aerial radiation and received RF energy.It is compared with the mechanical scanning antenna system, many significant advantages are arranged: phased array has been omitted whole antenna driving system, when wherein individual component breaks down, still keep higher reliability, the mean free error time of this radar scanner is more than the mean free error time long (growing approximately 10 times) of mechanical scanning radar antenna.Typical phased array is that the phase distribution of utilizing robot calculator control phase shifter to change on the antenna aperture realizes wave beam at spacescan, i.e. electronic scanning.
The advantages such as phased array antenna is many because of its function, mobility strong, sweep velocity is fast, reliability is high are widely used in all kinds of detections and tracking radar system.Phase shifter is the core component of phased array antenna most critical, and the performance of phased array antenna, volume, weight, cost and reliability all depend on employed phase shifter to a great extent.The phase shifter of at present phased array antenna use is mainly ferrite phase shifter and PIN diode phase shifter, these two kinds of phase shifters all have weak point separately, be difficult to satisfy the requirement that miniaturization, lighting, high reliability, high band that modern electronic technology proposes phased array antenna of new generation use, the generally use aspect military and civilian is limited by very large.Ferroelectric phase shifter is considered to the novel phase shifter that is expected to address these problems.The microwave dielectric material that is applied to ferroelectric phase shifter should satisfy following performance requriements: the adjustable rate of dielectric that (1) is high; (2) moderate specific inductivity; (3) low dielectric loss; (4) good temperature stability; (5) high dielectric strength.
The strontium-barium titanate ferroelectric ceramic(s) has stronger non-linear effect, can be by changing extra electric field obtaining different dielectric constant values, thus realize electromagnetic phase shift.This material at room temperature has non-linear strong, polarization speed is fast, leakage current is little, anti-disruptive strength high, Curie temperature is adjustable characteristics, thereby has a wide range of applications at aspects such as dielectric phase shifter, voltage controlled filters.But the microwave dielectric loss of strontium-barium titanate is too high, needs to be optimized.From the documents and materials of having published at present, the method that the overwhelming majority can reduce the strontium-barium titanate dielectric loss often makes its voltage-controlled adjustability reduce simultaneously.Therefore, how to guarantee the material of developing still to keep higher dielectric, nonlinear be to be badly in need of at present the technical bottleneck of capturing having under low-loss prerequisite.
Summary of the invention
The object of the present invention is to provide a kind of transition element doped barium-strontium titanate based composite ceramic, this composite ceramics dielectric loss is low, and simultaneously voltage-controlled adjustability is high.
For achieving the above object, the present invention takes following technical scheme:
A kind of transition element doped barium-strontium titanate based composite ceramic, its composition comprises the xM-Ba of 40wt% 0.6Sr 0.4TiO 3With the MgO of 60wt%, wherein M is transition metal, and x is transition metal M and Ba 0.6Sr 0.4TiO 3Mol ratio, span is 0.25%～1.25%.
A kind of optimal technical scheme is characterized in that: described transition metal is Fe, Co or Mn.
Another object of the present invention is to provide a kind of preparation method of above-mentioned transition element doped barium-strontium titanate based composite ceramic.
For achieving the above object, the present invention takes following technical scheme:
A kind of preparation method of transition element doped barium-strontium titanate based composite ceramic comprises the steps:
(1) presses Ba 0.6Sr 0.4TiO 3Chemical dosage ratio takes by weighing an amount of BaCO 3, SrCO 3And TiO 2Pack in the agate mixing tank, add agate ball and alcohol, at three roller mixer mixing 24h, the volume ratio of agate ball, alcohol and powder is 6: 2: 1, the gained mixed slurry is dried in 100 ℃ baking oven, carries out afterwards pre-burning in the 1100 ℃ * 4h atmospheric air, obtains Ba 0.6Sr 0.4TiO 3Powder;
(2) with the oxide compound of transition metal M and the Ba of step (1) gained 0.6Sr 0.4TiO 3Powder is packed in the agate mixing tank, makes mole number and the Ba of transition metal M in the oxide compound of transition metal M 0.6Sr 0.4TiO 3The mol ratio of powder is 0.25%～1.25%, according to the technique of step (1), mixes, oven dry, pre-burning, obtains M-Ba 0.6Sr 0.4TiO 3Powder;
(3) with the M-Ba of step (2) gained 0.6Sr 0.4TiO 3Powder and MgO powder be respectively in the ratio weighing of 40wt% and 60wt%, in the agate mixing tank of packing into, according to the technique of step (1), mixes, oven dry, pre-burning, obtains M-Ba 0.6Sr 0.4TiO 3/ MgO mixed powder;
(4) with the M-Ba of step (3) gained 0.6Sr 0.4TiO 3/ MgO mixed powder is through pressure single shaft cold-press process, and pressing pressure 25MPa is pressed into the test piece of diameter 20mm, thick 7～8mm, and then adopts isostatic cool pressing technique, and pressing pressure 200MPa is pressed into ceramic body;
(5) with the ceramic body of step (4) gained sintering 4 hours in air atmosphere, under the normal pressure, 1420 ℃ of high temperature, obtain M-Ba 0.6Sr 0.4TiO 3/ MgO composite ceramics.
A kind of optimal technical scheme is characterized in that: in the step (1), and described BaCO 3, SrCO 3Or TiO 2Purity be more than or equal to 99.5%.
A kind of optimal technical scheme is characterized in that: in the step (2), the oxide compound of described transition metal M is MnO 2, Fe 2O 3Or Co 2O 3
A kind of optimal technical scheme is characterized in that: in the step (2), and described MnO 2, Fe 2O 3Or Co 2O 3The granularity of powder is 0.3～0.5 μ m, purity 〉=99%.
A kind of optimal technical scheme is characterized in that: in the step (3), the granularity of described MgO powder is 0.3～0.5 μ m, purity 〉=99%.
1, compositional selecting of the present invention and composition proportion
Ba 1-ySr yTiO 3(BST) voltage-controlled adjustable rate and dielectric loss consumption all reduce along with the increase of y, in order to coordinate above two performance index, make material have higher voltage-controlled adjustable rate and lower dielectric loss, and the present invention is decided to be 0.4 with y.In addition, Ba 1-ySr yTiO 3The specific inductivity of pottery is too high, and when y=1, it is minimum that dielectric constant values reaches, and is 200～250, but the voltage-controlled adjustable rate of material is very low at this moment; Ba 0.6Sr 0.4TiO 3The specific inductivity of pottery is about 1500.Too high specific inductivity is difficult to satisfy the service requirements of dielectric phase shifter, so the present invention passes through Ba 0.6Sr 0.4TiO 3Compound moderate specific inductivity (about 100) and the higher temperature stability of obtaining of pottery and MgO.The present invention is with Ba 0.6Sr 0.4TiO 3Ba in the/MgO composite ceramics 0.6Sr 0.4TiO 3Be decided to be respectively 40wt% and 60wt% with the content of MgO.
2, Preparation Technique of Powders
Select purity greater than 99.5% BaCO 3, SrCO 3, TiO 2Powder adopts solid reaction process to prepare Ba 0.6Sr 0.4TiO 3Ceramic powder; Respectively with MnO 2, Fe 2O 3And Co 2O 3With Ba 0.6Sr 0.4TiO 3Mix, adopt solid reaction process to make respectively the M-Ba of Fe, Mn, Co doping 0.6Sr 0.4TiO 3Powder.With M-Ba 0.6Sr 0.4TiO 3Powder and superfine Mg O mix and obtain M-Ba 0.6Sr 0.4TiO 3/ MgO mixed powder is in order to moulding and sintering.
3, forming technique
With 2) in prepared M-Ba 0.6Sr 0.4TiO 3/ MgO composite ceramic material is through two-step approach compression moulding: at first be pressed into the test piece of diameter 20mm, thick 7～8mm through pressure single shaft cold-press process (pressing pressure 25MPa), and then adopt isostatic cool pressing technique (pressing pressure 200MPa) press ceramic base substrate, with density and the elimination base substrate internal stress that improves ceramic body.
4, densification technology
The gained base substrate places high temperature silicon molybdenum bar sintering oven, and sintering is 4 hours in air atmosphere, under the normal pressure, 1420 ℃ of high temperature, makes M-Ba 0.6Sr 0.4TiO 3/ MgO composite ceramics.Described sintering process as shown in Figure 1.
5, M-Ba 0.6Sr 0.4TiO 3The structural analysis of/MgO composite ceramics and performance test
Adopt the phase structure of MSAL XD2 type X-ray diffractometer (XRD) analysis of material, BEIF WCT-2C type differential thermal balance is analyzed Ba 1-ySr yTiO 3-Mg 1-xZn xThe thermodynamic property of O composite granule, Hitachi S-4800 type field emission scanning electron microscope (FE-SEM) is observed the ceramics sample microscopic appearance; AixaCCT TF2000 Ferroelectric analyser carries out the test of C-V (capacitance-voltage) curve and ferroelectric hysteresis loop; Adopt high-frequency dielectric constant and the dielectric loss of Agilent E8363A test material; Adopt the dielectric strength of Trek 30/20 type high voltage amplifier system testing stupalith.
The invention has the advantages that:
1) selects xM-Ba 0.6Sr 0.4TiO 3/ MgO (M=Fe, Co, Mn) matrix material has improved traditional B a 1-ySr yTiO 3The sintering character of the voltage-controlled adjustable pottery of/MgO.
XM-Ba 0.6Sr 0.4TiO 3X is M and Ba in/the MgO formula 0.6Sr 0.4TiO 3Mol ratio (x=0.25%～1.25%).At present, be Ba for the ferroelectric ceramic(s) overwhelming majority who makes phase shifter 1-ySr yTiO 3-MgO composite ceramics.Wherein, the effect of MgO is to reduce Ba 1-ySr yTiO 3Specific inductivity and high frequency (〉=1GHz) dielectric loss.The present invention adopts M doping Ba 0.6Sr 0.4TiO 3Ba in the acceleration of sintering process 0.6Sr 0.4TiO 3Crystal grain grow, adopt simultaneously superfine Mg O powder to reduce sintering temperature.
2) to Ba 0.6Sr 0.4TiO 3Carrying out M mixes and can not reduce (even increasing) xM-Ba 0.6Sr 0.4TiO 3Under the prerequisite of the voltage-controlled adjustable rate of/MgO pottery, the dielectric loss of decrease material.
M mixes can improve Ba 0.6Sr 0.4TiO 3Intrinsic oxygen room characteristic and Ba in/the MgO composite ceramics 0.6Sr 0.4TiO 3The lattice parameter of pottery, thereby the extrinsic dielectric loss of reduction composite ceramics.In addition, M mixes to being in paraelectric state Ba 0.6Sr 0.4TiO 3The impact of the anharmonic coefficient of/MgO pottery is little, therefore the voltage-controlled adjustable rate of material is obviously reduced, even when M doping value is in a certain suitable scope, also can one the non-true coefficient of writing of composite ceramics is improved, thus the voltage-controlled adjustable rate of raising material.Can satisfy the service requirements of microwave dielectric material fully
The present invention will be further described below by the drawings and specific embodiments, but and do not mean that limiting the scope of the invention.
Description of drawings
Fig. 1 M-Ba 0.6Sr 0.4TiO 3The sintering process of/MgO pottery;
Fig. 2 Mn-Ba 0.6Sr 0.4TiO 3The XRD analysis result of pottery;
Fig. 3 Mn-Ba 0.6Sr 0.4TiO 3The Fe-SME pattern of pottery;
Fig. 4 Fe-Ba 0.6Sr 0.4TiO 3The XRD analysis result of pottery;
Fig. 5 Fe-Ba 0.6Sr 0.4TiO 3The Fe-SEM pattern of pottery;
Fig. 6 Co-Ba 0.6Sr 0.4TiO 3The XRD analysis result of pottery;
Fig. 7 Co-Ba 0.6Sr 0.4TiO 3The Fe-SEM pattern of pottery.
Embodiment
Embodiment 1
Press Ba 0.6Sr 0.4TiO 3(BST) chemical dosage ratio takes by weighing an amount of BaCO 3, SrCO 3And TiO 2In powder (purity all 〉=99.5%) the agate mixing tank of packing into, add agate ball and alcohol, at the mixed 24h of three roller mixers, the volume ratio of agate ball, alcohol and powder is 6: 2: 1.Above-mentioned mixed slurry is dried in 100 ℃ baking oven, carry out afterwards pre-burning in the 1100 ℃ * 4h atmospheric air, obtain Ba 0.6Sr 0.4TiO 3Powder.
Press above-mentioned mixing procedure with MnO 2Powder (granularity is 0.3～0.5 μ m, purity 〉=99%) and Ba 0.6Sr 0.4TiO 3Powder mixes, MnO 2With Ba 0.6Sr 0.4TiO 3The mol ratio of powder gets respectively 0.0%, 0.25%, 0.50%, 0.75%, 1.00% and 1.25%.With mixed powder oven dry, carry out afterwards pre-burning in the 1100 ℃ * 4h atmospheric air, make Mn doping Ba 0.6Sr 0.4TiO 3Powder (Mn-Ba 0.6Sr 0.4TiO 3), the XRD analysis result of this powder is as shown in Figure 2.As seen, all M-BST powder have all formed single cubic perovskite structure, do not find the diffraction peak of other dephasign.
With Mn-Ba 0.6Sr 0.4TiO 3Powder and MgO powder (granularity is 0.3～0.5 μ m, purity 〉=99%) in the ratio weighing of 40wt% and 60wt%, with same mixing procedure mixing and oven dry, obtain Mn-Ba respectively 0.6Sr 0.4TiO 3/ MgO mixed powder.With Mn-Ba 0.6Sr 0.4TiO 3/ MgO mixed powder is through pressure single shaft cold-press process, and pressing pressure 25MPa is pressed into the test piece of diameter 20mm, thick 7～8mm, and then adopts isostatic cool pressing technique, and pressing pressure 200MPa is pressed into ceramic body; The ceramic body of gained places high temperature silicon molybdenum bar sintering oven, and sintering carried out densification in 4 hours in air atmosphere, under the normal pressure, 1420 ℃ of high temperature, and sintering process obtains Mn-Ba as shown in Figure 1 0.6Sr 0.4TiO 3/ MgO composite ceramics.
The section SEM pattern of this composite ceramic material as shown in Figure 3, (a)-(f) among Fig. 3 is respectively x=0.0%, 0.25%, 0.50%, 0.75%, 1.00%, 1.25% Mn-Ba 0.6Sr 0.4TiO 3The section SEM pattern of/MgO composite ceramics.As seen all ceramics samples all show the dense non-porous two phase structure, and the more shallow zone of color is Mn-BST phase (being the BST phase among a) in the photo, and the darker zone of color then is the MgO phase.The grain-size of Mn-BST phase is about 1～2 μ m, and the grain-size of MgO then is 2～4 μ m.The grain-size of all samples is basically identical, and the change with transition element doped content does not have considerable change.It should be noted that and can find some sizes less than the abundant BST particle of growth of 500nm in the sample that do not mix, and along with the increasing of Mn doping, tiny BST particle reduces or disappears, crystal grain is grown and is become better and better.This shows that the Mn doping can improve the sintering character of BST.
With Mn-Ba 0.6Sr 0.4TiO 3/ MgO composite ceramics block is processed into the sequin of φ 15mm * 0.5mm, adopts the mode of silk screen printing to be coated with upper temperature silver paste at two ends, then carries out 600 ℃ * 15min sintering, is prepared into the ceramics sample of coating silver electrode.Utilize the ferroelectric analyser of TF-2000 to test the C-V curve of above-mentioned sample, the voltage-controlled adjustable rate that calculates is as shown in table 1.As seen Mn mixes and can improve Mn-Ba 0.6Sr 0.4TiO 3The voltage-controlled adjustable rate of/MgO composite ceramics.With Mn-Ba 0.6Sr 0.4TiO 3/ MgO ceramic block is processed into the small column of φ 10mm * 5mm, carries out the test of microwave frequency band dielectric properties at Agilent E8363A network analyzer afterwards, and the result who records is as shown in table 1.As seen, Mn mixes and can make the microwave dielectric loss decrease of material.Mn-Ba 0.6Sr 0.4TiO 3The breaking down field strength test result of/MgO ceramic block is as shown in table 1, and as seen, the breaking down field strength of sample can satisfy service requirements fully all greater than 30kV/mm.
Embodiment 2
Press Ba 0.6Sr 0.4TiO 3Chemical dosage ratio takes by weighing an amount of BaCO 3, SrCO 3And TiO 2In (purity difference 〉=99.5%) the agate mixing tank of packing into, add agate ball and alcohol, at the mixed 24h of three roller mixers, the volume ratio of agate ball, alcohol and powder is 6: 2: l.Above-mentioned mixed slurry is dried in 100 ℃ baking oven, carry out afterwards pre-burning in the 1100 ℃ * 4h atmospheric air, obtain Ba 0.6Sr 0.4TiO 3Powder.Press above-mentioned mixing procedure with Fe 2O 3Powder (granularity is 0.3～0.5 μ m, purity 〉=99%) and Ba 0.6Sr 0.4TiO 3Powder mixes, Fe 2O 3Middle Fe and Ba 0.6Sr 0.4TiO 3The mol ratio of powder gets respectively 0.0%, 0.25%, 0.50%, 0.75%, 1.00% and 1.25%.With mixed powder oven dry, carry out afterwards pre-burning in the 1100 ℃ * 4h atmospheric air, make Fe doping Ba 0.6Sr 0.4TiO 3Powder (Fe-Ba 0.6Sr 0.4TiO 3), the XRD analysis result of this powder is as shown in Figure 4.As seen, all Fe-BST powder have all formed single cubic perovskite structure, do not find the diffraction peak of other dephasign.
With Fe-Ba 0.6Sr 0.4TiO 3Powder and MgO powder (granularity is 0.3～0.5 μ m, purity 〉=99%) in the ratio weighing of 40wt% and 60wt%, with same mixing procedure mixing and oven dry, obtain Fe-Ba respectively 0.6Sr 0.4TiO 3/ MgO mixed powder.Carry out afterwards axial compression and cold isostatic compaction.Place high temperature silicon molybdenum bar sintering oven to carry out densification by sintering process shown in Figure 1 ceramic blank after the moulding, make Fe-Ba 0.6Sr 0.4TiO 3/ MgO composite ceramics.The section SEM pattern of this composite ceramic material as shown in Figure 5, (a)-(f) among Fig. 5 is respectively x=0.0%, 0.25%, 0.50%, 0.75%, 1.00%, 1.25% Fe-Ba 0.6Sr 0.4TiO 3The section SEM pattern of/MgO composite ceramics.As seen all ceramics samples all show the dense non-porous two phase structure, and the more shallow zone of color is Fe-BST phase (being the BST phase among a) in the photo, and the darker zone of color then is the MgO phase.The grain-size of Fe-BST phase is about 1～2 μ m, and the grain-size of MgO then is 2～4 μ m.The grain-size of all samples is basically identical, and the change with transition element doped content does not have considerable change.It should be noted that and can find some sizes less than the abundant BST particle of growth of 500nm in the sample that do not mix, and along with the increasing of Fe doping, tiny BST particle reduces or disappears, crystal grain is grown and is become better and better.This shows that the Fe doping can improve the sintering character of BST.
With Fe-Ba 0.6Sr 0.4TiO 3/ MgO composite ceramics block is processed into the sequin of φ 15mm * 0.5mm, adopts the mode of silk screen printing to be coated with upper temperature silver paste at two ends, then carries out 600 ℃ * 15min sintering, is prepared into the ceramics sample of coating silver electrode.Utilize the ferroelectric analyser of TF-2000 to test the C-V curve of above-mentioned sample, the voltage-controlled adjustable rate that calculates is as shown in table 2.As seen Fe-Ba after Fe mixes 0.6Sr 0.4TiO 3The voltage-controlled adjustable rate of/MgO composite ceramics with mix before do not compare change little.With Fe-Ba 0.6Sr 0.4TiO 3/ MgO ceramic block is processed into the small column of φ 10mm * 5mm, carries out the test of microwave frequency band dielectric properties at Agilent E8363A network analyzer afterwards, and the result who records is as shown in table 2.As seen, Fe mixes and can make the microwave dielectric loss decrease of material.Fe-Ba 0.6Sr 0.4TiO 3The breaking down field strength test result of/MgO ceramic block is as shown in table 2, and as seen, the breaking down field strength of sample can satisfy the service requirements of dielectric phase shifter fully all greater than 32kV/mm.
Embodiment 3
Press Ba 0.6Sr 0.4TiO 3Chemical dosage ratio takes by weighing an amount of BaCO 3, SrCO 3And TiO 2In (purity all 〉=99.5%) agate mixing tanks of packing into, add agate ball and alcohol, at the mixed 24h of three roller mixers, the volume ratio of agate ball, alcohol and powder is 6: 2: 1.Above-mentioned mixed slurry is dried in 100 ℃ baking oven, carry out afterwards pre-burning in the 1100 ℃ * 4h atmospheric air, obtain Ba 0.6Sr 0.4TiO 3Powder.Press above-mentioned mixing procedure with Co 2O 3Powder (granularity is 0.3～0.5 μ m, purity 〉=99%) and Ba 0.6Sr 0.4TiO 3Powder mixes, Co 2O 3Middle Co and Ba 0.6Sr 0.4TiO 3The mol ratio of powder gets respectively 0.0%, 0.25%, 0.50%, 0.75%, 1.00% and 1.25%.With mixed powder oven dry, carry out afterwards pre-burning in the 1100 ℃ * 4h atmospheric air, make Co doping Ba 0.6Sr 0.4TiO 3Powder (Co-Ba 0.6Sr 0.4TiO 3), the XRD analysis result of this powder is as shown in Figure 6.As seen, all Co-BST powder have all formed single cubic perovskite structure, do not find the diffraction peak of other dephasign.
With Co-Ba 0.6Sr 0.4TiO 3Powder and MgO powder (granularity is 0.3～0.5 μ m, purity 〉=99%) in the ratio weighing of 40wt% and 60wt%, with same mixing procedure mixing and oven dry, obtain Co-Ba respectively 0.6Sr 0.4TiO 3/ MgO mixed powder.Carry out afterwards axial compression and cold isostatic compaction.Place high temperature silicon molybdenum bar sintering oven to carry out densification by sintering process shown in Figure 1 ceramic blank after the moulding, make Co-Ba 0.6Sr 0.4TiO 3/ MgO composite ceramics.The section SEM pattern of this composite ceramic material as shown in Figure 7, (a)-(f) among Fig. 7 is respectively x=0.0%, 0.25%, 0.50%, 0.75%, 1.00%, 1.25% Co-Ba 0.6Sr 0.4TiO 3The section SEM pattern of/MgO composite ceramics.As seen all ceramics samples all show the dense non-porous two phase structure, and the more shallow zone of color is Co-BST phase (being the BST phase among a) in the photo, and the darker zone of color then is the MgO phase.The grain-size of Co-BST phase is about 1～2 μ m, and the grain-size of MgO then is 2～4 μ m.The grain-size of all samples is basically identical, and the change with transition element doped content does not have considerable change.It should be noted that and can find some sizes less than the abundant BST particle of growth of 500nm in the sample that do not mix, and along with the increasing of Co doping, tiny BST particle reduces or disappears, crystal grain is grown and is become better and better.This shows that the Co doping can improve the sintering character of BST.
With Co-Ba 0.6Sr 0.4TiO 3/ MgO composite ceramics block is processed into the sequin of φ 15mm * 0.5mm, adopts the mode of silk screen printing to be coated with upper temperature silver paste at two ends, then carries out 600 ℃ * 15min sintering, is prepared into the ceramics sample of coating silver electrode.Utilize the ferroelectric analyser of TF-2000 to test the C-V curve of above-mentioned sample, the voltage-controlled adjustable rate that calculates is as shown in table 3.As seen Co-Ba after Co mixes 0.6Sr 0.4TiO 3The voltage-controlled adjustable rate of/MgO composite ceramics with mix before do not compare slightly and reduce, generally speaking change little.With Co-Ba 0.6Sr 0.4TiO 3/ MgO ceramic block is processed into the small column of φ 10mm * 5mm, carries out the test of microwave frequency band dielectric properties at Agilent E8363A network analyzer afterwards, and the result who records is as shown in table 3.As seen, Co mixes and can make the microwave dielectric loss decrease of material.Co-Ba 0.6Sr 0.4TiO 3The breaking down field strength test result of/MgO ceramic block is as shown in table 3, and as seen, the breaking down field strength of sample can satisfy the service requirements of dielectric phase shifter fully all greater than 28kV/mm.
Table 1, Mn-Ba 0.6Sr 0.4TiO 3The dielectric properties of pottery
Mn doping mol.% Dielectric constant Dielectric loss tan δ Test frequency GHz Voltage-controlled adjustable rate % Disruptive strength kV/mm
0.00 108.797 0.008 3.988 22.38 25
0.25 136.147 0.0055 3.574 27.30 30
0.50 131.777 0.0045 3.645 27.27 32
0.75 112.286 0.0047 3.922 27.22 31.5
1.0 111.801 0.0047 3.935 27.31 30.5
1.25 111.142 0.0047 3.982 25.15 31
Table 2, Fe-Ba 0.6Sr 0.4TiO 3The dielectric properties of pottery
Fe doping mol.% Dielectric constant Dielectric loss tan δ Test frequency GHz Voltage-controlled adjustable rate % Disruptive strength kV/mm
0.00 108.797 0.008 3.988 22.38 25
0.25 107.875 5.4 4.023 21.07 32.2
0.50 105.882 4.7 4.064 23.24 32
0.75 103.554 4.5 4.11 23.74 33.5
1.0 105.667 4.2 4.076 21.91 31.5
1.25 114.919 5.3 3.906 23.95 31
Table 3, Co-Ba 0.6Sr 0.4TiO 3The dielectric properties of pottery
Co doping mol.% Dielectric constant Dielectric loss tan δ Test frequency GHz Voltage-controlled adjustable rate % Disruptive strength kV/mm
0.00 108.797 0.008 3.988 22.38 25
0.25 126.128 0.0034 3.721 21.03 30
0.50 122.851 0.0051 3.794 20.28 29.5
0.75 127.096 0.0053 3.767 24.33 30
1.0 113.014 0.0049 3.946 20.15 29
1.25 123.442 0.0051 3.767 22.51 28.3

Claims (4)

1. the preparation method of a transition element doped barium-strontium titanate based composite ceramic comprises the steps:
(1) presses Ba 0.6Sr 0.4TiO 3Chemical dosage ratio takes by weighing an amount of BaCO 3, SrCO 3And TiO 2Pack in the agate mixing tank, add agate ball and alcohol, at three roller mixer mixing 24h, the volume ratio of agate ball, alcohol and powder is 6: 2: 1, the gained mixed slurry is dried in 100 ℃ baking oven, carries out afterwards pre-burning in the 1100 ℃ * 4h atmospheric air, obtains Ba 0.6Sr 0.4TiO 3Powder;
(2) with the oxide compound of transition metal M and the Ba of step (1) gained 0.6Sr 0.4TiO 3Powder is packed in the agate mixing tank, makes mole number and the Ba of transition metal M in the oxide compound of transition metal M 0.6Sr 0.4TiO 3The mol ratio of powder is 0.25%～1.25%, according to the technique of step (1), mixes, oven dry, pre-burning, obtains M-Ba 0.6Sr 0.4TiO 3Powder; The oxide compound of described transition metal M is MnO 2, Fe 2O 3Or Co 2O 3
(3) with the M-Ba of step (2) gained 0.6Sr 0.4TiO 3Powder and MgO powder be respectively in the ratio weighing of 40wt% and 60wt%, in the agate mixing tank of packing into, according to the technique of step (1), mixes, oven dry, pre-burning, obtains M-Ba 0.6Sr 0.4TiO 3/ MgO mixed powder;
(4) with the M-Ba of step (3) gained 0.6Sr 0.4TiO 3/ MgO mixed powder is through pressure single shaft cold-press process, and pressing pressure 25MPa is pressed into the test piece of diameter 20mm, thick 7～8mm, and then adopts isostatic cool pressing technique, and pressing pressure 200MPa is pressed into ceramic body;
(5) with the ceramic body of step (4) gained sintering 4 hours in air atmosphere, under the normal pressure, 1420 ℃ of high temperature, obtain M-Ba 0.6Sr 0.4TiO 3/ MgO composite ceramics.
2. the preparation method of transition element doped barium-strontium titanate based composite ceramic according to claim 1 is characterized in that: in the step (1), and described BaCO 3, SrCO 3Or TiO 2Purity be more than or equal to 99.5%.
3. the preparation method of transition element doped barium-strontium titanate based composite ceramic according to claim 2 is characterized in that: described MnO 2, Fe 2O 3Or Co 2O 3The granularity of powder is 0.3～0.5 μ m, purity 〉=99%.
4. the preparation method of transition element doped barium-strontium titanate based composite ceramic according to claim 1, it is characterized in that: in the step (3), the granularity of described MgO powder is 0.3～0.5 μ m, purity 〉=99%.
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Ran-Young Kim et al..Dielectric properties of Mn-Doped BST thin films for microwave application.《Integrated Ferroelectrics》.2004,第66卷摘要. *
Wontae Chang et al..MgO-mixed Ba0.6Sr0.4TiO3 bulk ceramics and thin films for tunable microwave applications.《Journal of Applied Physics》.2002,第92卷(第7期),第3941页实验部分,及第3942页结果与讨论部分. *

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