CN103073285A - Microwave dielectric ceramic with low loss and medium dielectric constant and a preparation technology thereof - Google Patents

Abstract

The invention relates to a microwave dielectric ceramic with low loss and a medium dielectric constant and a preparation technology thereof. xCaTiO3*yLa2O3*zAl2O3+awt%Al2O3 serves as a principal component, Al2O3 is an auxiliary component, a suitable parameter is used, and the technical difficulty that the sintering temperature is high and the material Q is low in a process of La replacing Nd is successfully solved. The microwave dielectric ceramic with low loss and the medium dielectric constant and the preparation technology thereof have the advantages that the cost can be remarkably reduced by replacing La2O3 with Nd2O3; Q*f0 is improved; and the sintering temperature is decreased, and energy is saved.

Description

A kind of low-loss microwave dielectric ceramic with medium dielectric constant and preparation technology thereof

Technical field

The invention belongs to microwave-medium ceramics prescription of a kind of high quality factor and preparation method thereof, particularly a MTiO ₃-LnAlO ₃It is composite perofskite microwave dielectric material and preparation method thereof.Be widely used in the systems such as mobile telephone, automobile telephone, telestar receptor, Global Positioning System, wireless local access and various radars.

Background technology

Microwave-medium ceramics is the core material of microwave device.Because microwave technology equipment is to miniaturization and integrated, especially civilian in enormous quantities, low price direction develop rapidly, have developed large quantities of microwave dielectric ceramic materials for various microwave frequency bands at present.Be applied to the media ceramic of microwave circuit, must satisfy following dielectric characterization and require: 1) higher relative permittivity Er, the general size of determining the medium ceramic material relative permittivity according to applying frequency.When applying frequency is 0.8 ~ 4GHz (low side), Er＞50; During 4 ~ 8GHz (middle-end), 30≤Er≤50; During 8 ~ 18GHz (middle-end), Er≤30; 2) high quality factor q is to improve selecting frequency characteristic, general requirement Q * f ₀〉=5000; 3) approaching zero frequency-temperature coefficient τ f has good temperature stability to guarantee device, and the dielectric resonance device generally all is that the frequency of certain vibration modes of microwave-medium ceramics is as its mid-frequency.If τ f is large, then show the variation that the mid-frequency of device will Yin Wendu and produce large drift, device can't high stable work.In the microwave dielectric ceramic with medium dielectric constant system, MTiO ₃-LnAlO ₃(M:Sr, Ca; Ln:La, Nd, Sm) CaTiO in being ₃-NdAlO ₃Excellent microwave dielectric property is arranged, be widely used in middle-dielectric constant microwave-medium ceramic material, relatively practicality microwave CaTiO ₃-NdAlO ₃Have the following disadvantages: 1) CaTiO ₃-NdAlO ₃The based material sintering temperature is higher, 1600 ℃ of ability densification potteries; 2) CaTiO ₃-NdAlO ₃System, Q * f ₀≤ 30000; 3) price along with rare earth element nd rises steadily, and does not meet the developing direction of microwave dielectric ceramic materials low price.

Summary of the invention

The present invention is directed to defects, purpose is catered to the miniaturization of tracking exchage microwave frequency, high frequencyization needs, aims to provide one and has microwave-medium ceramics prescription of high quality factor and preparation method thereof, with CaTiO ₃-LnAlO ₃Be that system is research object, adopt Al ₂O ₃Be sintering aid, the collaborative sintering temperature that reduces pottery is adjusted principal crystalline phase and is formed the microwave dielectric property of comprehensive regulation material.

The technical solution used in the present invention is for this reason: the present invention is with xCaTiO3yLa ₂O ₃Z Al ₂O ₃+ awt% Al ₂O ₃For becoming main minute, Al ₂O ₃Be minor component, 0.6≤x≤0.8,0. 1≤y≤0.2,0. 1≤z≤0.2,0.04≤a≤0.16 wherein, wherein x, y, z are that mol ratio is added, a adds with mass percent, awt% is for accounting for x CaTiO ₃YLa ₂O ₃Z Al ₂O ₃Mass percent.

Described x is 0.664, y is 0.168, z is 0.168, a is 0.12.

A kind of preparation technology of low-loss microwave dielectric ceramic with medium dielectric constant may further comprise the steps:

1) first calcium titanate, analytical pure lanthanum oxide, spectroscopically pure alchlor are pressed xCaTiO ₃YLa ₂O ₃Z Al ₂O ₃The chemical formula batching is mixed, at 1200-1280 ℃ of pre-burning 3.5-4.5h, and synthetic principal constituent x CaTiO ₃YLa ₂O ₃Z Al ₂O ₃, wherein: 0.6≤x≤0.8,0. 1≤y≤0.2,0.1≤z≤0.2,0.04≤a≤0.16;

2) with synthetic principal constituent x CaTiO ₃YLa ₂O ₃Z Al ₂O ₃And minor component Al ₂O ₃Raw material is pressed x CaTiO ₃YLa ₂O ₃Z Al ₂O ₃+ awt% Al ₂O ₃Synthetic, wherein: 0.6≤x≤0.8,0. 1≤y≤0.2,0.1≤z≤0.2,0.04≤a≤0.16, awt% is for accounting for xCaTiO ₃YLa ₂O ₃Z Al ₂O ₃Mass percent, obtain the powder for the preparation of the low-loss microwave dielectric ceramic with medium dielectric constant after the mixing, powder pressing is become circle sheet, at 1420 ℃ of-1600 ℃ of sintering, the insulation 5-7h.

1) in the step, each material is placed polyurethane ball-milling pot, add berkelium oxide ball and deionization water mill, material wherein: deionized water: the berkelium ball weight is than being 1:1.5:2 ~ 4.5, mixing and ball milling post-drying in the QM-BP planetary ball mill, 1200-1280 ℃ of pre-burning 3.5-4.5h in box-type furnace synthesizes principal constituent xCaTiO afterwards ₃YLa ₂O ₃ZAl ₂O ₃

2) in the step, with synthetic principal constituent x CaTiO ₃YLa ₂O ₃Z Al ₂O ₃And awt% Al ₂O ₃Raw material is pressed porcelain and is formed batching, places polyurethane ball-milling pot, adds berkelium oxide ball and deionization water mill post-drying, adds the poly (vinyl alcohol) binder granulation, after make circle sheet, at 1420 ℃ of-1600 ℃ of sintering, insulation 5-7h.

The present invention who adopts above-mentioned prescription and preparation method to form can obtain Er=44.2-45.1, high quality factor, and the microwave-medium ceramics of low resonant frequency coefficient τ f, performance index can satisfy the microwave dielectric ceramic materials requirement.

The present invention and the existing CaTiO that generally adopts ₃-NdAlO ₃Medium dielectric constant microwave medium system compares, and successfully solve La and replace in the Nd process, the Q technological difficulties on the low side of sintering temperature height and material, advantage of the present invention is following three advantages: 1) La ₂O ₃Replace Nd ₂O ₃Can be significantly reduced to this; 2) improve Q * f ₀3) reduce sintering temperature, saved the energy.

Description of drawings

Fig. 1,2,3 is the trial curve figure of each characteristic parameter of the present invention.

Embodiment

The present invention at first presses x CaTiO with calcium titanate, analytical pure lanthanum oxide, spectroscopically pure alchlor ₃YLa ₂O ₃Z Al ₂O ₃Chemical formula batching places polyurethane ball-milling pot, adds berkelium oxide ball and deionization water mill post-drying, after the oven dry in box-type furnace 1200-1280 ℃ of pre-burning 3.5-4.5h, synthetic principal constituent xCaTiO ₃YLa ₂O ₃ZAl ₂O ₃

With synthetic principal constituent x CaTiO ₃YLa ₂O ₃Z Al ₂O ₃And awt% Al ₂O ₃Raw material is pressed porcelain and is formed batching, places polyurethane ball-milling pot, adds berkelium oxide ball and deionization water mill post-drying, add the granulation of 12wt% polyvinyl alcohol (PVA) tackiness agent, then be pressed into diameter 15mm, the circle sheet of thickness 7.5mm, at 1420 ℃ of-1600 ℃ of sintering, insulation 5-7h.

For the dielectric properties of measure sample, at first the cylindrical ceramic sample is polished at 1200 order silicon carbide papers, then it is cleaned in alcohol with ultrasonic wave.Adopt Ailment E5071B network analyzer, according to the transverse electric field (TE of cavity method with microwave frequency ₀₁₁Mould) dielectric properties of analytic sample, test frequency is at 4～5GHz.Obtain the temperature coefficient of resonance frequency of sample by the resonant frequency variation with temperature rate of measuring media resonator, the temperature range of measurement is-40 ℃～85 ℃.Al ₂O ₃Adding effectively promoted the densification of matrix, the sintering structure that obtains in 1420 ℃～1500 ℃ sintering ranges is fine and close, pore is few.Make the pore decline of matrix along with the gradually rising of sintering temperature, pore is disappeared in the rising of temperature and the crystal boundary moving hormany carries out, but acceleration of sintering matrix densification, raising system specific inductivity, the weak contact ion of the sintering matrix inside of high densification is few, the sintered compact loss is also less, and relevant each characteristic parameter is tested diagram referring to each, sees Fig. 1,2,3.

The present invention adopts parameters, the performance that obtains such as following table:

Numbering	x	Y	z	a	Best sintering temperature	Er:	Q*f0	τf
									1	0.674	0.163	0.163	0	1600℃	45.1	37643	+15.5
2	0.664	0.168	0.168	0	1600℃	44.4	38246	+4.5
									3	0.654	0.173	0.173	0	1600℃	44.2	40976	-10.5
4	0.664	0.170	0.166	0	1600℃	44.5	37536	+5.2
									5	0.664	0.168	0.168	0.04	1540℃	44.2	43707	6.4
6	0.664	0.168	0.168	0.08	1480℃	44.4	45308	2.8
									7	0.664	0.168	0.168	0.12	1450℃	44.5	46258	4.5
8	0.664	0.168	0.168	0.16	1420℃	44.3	43781	4.8

By table as seen, along with x increases, the Er of ceramics sample increases, quality factor q * f ₀Value reduces, and τ f moves to the positive temperature coefficient direction.The addition of x can be regulated τ f and the Er of material, can be at Q*f ₀In the value allowed band, regulate τ f and Er.Al mixes after principal crystalline phase is synthetic and reduces the sintering warm area, when Al content increases, and Q*f ₀Value increases afterwards first and lowers.Sintering temperature progressively reduces.

As seen from table, in this enforcement properties optimal components, x=0.664, y=0.168, z=0.168 a=0.12, component o'clock have best microwave dielectric property at 1450 ℃ of sintering: Er=44.5, Q*f ₀=46258GHz, τ f=4.8PPm.

Claims (5)

1. a low-loss microwave dielectric ceramic with medium dielectric constant is characterized in that, with xCaTiO3yLa ₂O ₃Z Al ₂O ₃+ awt% Al ₂O ₃For becoming main minute, Al ₂O ₃Be minor component, 0.6≤x≤0.8,0. 1≤y≤0.2,0. 1≤z≤0.2,0.04≤a≤0.16 wherein, wherein x, y, z are that mol ratio is added, a adds with mass percent, awt% is for accounting for x CaTiO ₃YLa ₂O ₃Z Al ₂O ₃Mass percent.

2. a kind of low-loss microwave dielectric ceramic with medium dielectric constant according to claim 1 is characterized in that, described x is 0.664, y is 0.168, z is 0.168, a is 0.12.

3. the preparation technology of a low-loss microwave dielectric ceramic with medium dielectric constant is characterized in that, may further comprise the steps:

1) first calcium titanate, analytical pure lanthanum oxide, spectroscopically pure alchlor are pressed xCaTiO ₃YLa ₂O ₃Z Al ₂O ₃The chemical formula batching is mixed, at 1200-1280 ℃ of pre-burning 3.5-4.5h, and synthetic principal constituent x CaTiO ₃YLa ₂O ₃Z Al ₂O ₃, wherein: 0.6≤x≤0.8,0. 1≤y≤0.2,0.1≤z≤0.2,0.04≤a≤0.16;

2) with synthetic principal constituent x CaTiO ₃YLa ₂O ₃Z Al ₂O ₃And minor component Al ₂O ₃Raw material is pressed x CaTiO ₃YLa ₂O ₃Z Al ₂O ₃+ awt% Al ₂O ₃Synthetic, wherein: 0.6≤x≤0.8,0. 1≤y≤0.2,0.1≤z≤0.2,0.04≤a≤0.16, awt% is for accounting for xCaTiO ₃YLa ₂O ₃Z Al ₂O ₃Mass percent, obtain the powder for the preparation of the low-loss microwave dielectric ceramic with medium dielectric constant after the mixing, powder pressing is become circle sheet, at 1420 ℃ of-1600 ℃ of sintering, the insulation 5-7h.

4. the preparation technology of a kind of low-loss microwave dielectric ceramic with medium dielectric constant according to claim 3, it is characterized in that, 1) in the step, each material is placed polyurethane ball-milling pot, add berkelium oxide ball and deionization water mill, wherein material: deionized water: the berkelium ball weight is than being 1:1.5:2 ~ 4.5, mixing and ball milling post-drying in the QM-BP planetary ball mill, 1200-1280 ℃ of pre-burning 3.5-4.5h in box-type furnace synthesizes principal constituent xCaTiO afterwards ₃YLa ₂O ₃ZAl ₂O ₃

5. the preparation technology of a kind of low-loss microwave dielectric ceramic with medium dielectric constant according to claim 3 is characterized in that,

2) in the step, with synthetic principal constituent x CaTiO ₃YLa ₂O ₃Z Al ₂O ₃And awt% Al ₂O ₃Raw material is pressed porcelain and is formed batching, places polyurethane ball-milling pot, adds berkelium oxide ball and deionization water mill post-drying, adds the poly (vinyl alcohol) binder granulation, after make circle sheet, at 1420 ℃ of-1600 ℃ of sintering, insulation 5-7h.

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