EP0705230A1 - NOUVEAU MATERIAU COMPOSITE CERAMIQUE FERROELECTRIQUE A BASE DE BSTO/MgO - Google Patents

NOUVEAU MATERIAU COMPOSITE CERAMIQUE FERROELECTRIQUE A BASE DE BSTO/MgO

Info

Publication number
EP0705230A1
EP0705230A1 EP94920023A EP94920023A EP0705230A1 EP 0705230 A1 EP0705230 A1 EP 0705230A1 EP 94920023 A EP94920023 A EP 94920023A EP 94920023 A EP94920023 A EP 94920023A EP 0705230 A1 EP0705230 A1 EP 0705230A1
Authority
EP
European Patent Office
Prior art keywords
bsto
magnesia
dielectric constant
materials
strontium titanate
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP94920023A
Other languages
German (de)
English (en)
Other versions
EP0705230A4 (fr
Inventor
Louise C. Sengupta
Eric Ngo
Steven Stowell
Michelina E. O'day
Robert Lancto
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
US Department of Health and Human Services
United States Department of the Army
Original Assignee
US Department of Health and Human Services
United States Department of the Army
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from US08/076,291 external-priority patent/US5312790A/en
Application filed by US Department of Health and Human Services, United States Department of the Army filed Critical US Department of Health and Human Services
Publication of EP0705230A1 publication Critical patent/EP0705230A1/fr
Publication of EP0705230A4 publication Critical patent/EP0705230A4/fr
Withdrawn legal-status Critical Current

Links

Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q1/00—Details of, or arrangements associated with, antennas
    • H01Q1/36—Structural form of radiating elements, e.g. cone, spiral, umbrella; Particular materials used therewith
    • H01Q1/38—Structural form of radiating elements, e.g. cone, spiral, umbrella; Particular materials used therewith formed by a conductive layer on an insulating support
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/01—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics
    • C04B35/46—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on titanium oxides or titanates
    • C04B35/462—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on titanium oxides or titanates based on titanates
    • C04B35/465—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on titanium oxides or titanates based on titanates based on alkaline earth metal titanates

Definitions

  • the present invention deals with novel ceramic ferroelectric materials having ideal properties for use, for example, in phased array antenna systems.
  • the ferroelectric materials are a replacement for the more expensive current driven ferrites which are currently used in phased array antennas.
  • the invention outlines ferroelectric materials which provide adequate phase shift with a minimal insertion loss.
  • the present invention provides for improved materials which exhibit electronic properties which can be adjusted for use, for example, in any discrete element phase shifter design — i.e. planar microstrip, wave guide geometries or parallel plate structure.
  • the invention herein is superior to other currently used ferroelectric materials in the art.
  • the invention is designed to provide tunable materials with an extremely minimal insertion loss. Therefore, these materials can be used in millimeter wave applications with 77 GHz frequency range.
  • the subject matter of the present invention relates to the fabrication of specific ceramic materials which have sought after properties in, for example, phased array antenna systems.
  • the sought after properties include (1) a moderate dielectric constant; (2) a low loss; and (3) high tunability.
  • Dielectric constant is related to the energy storage in the material; whereas, the loss tangent is related to the power dissipation in the same material.
  • Tunability may be defined as ( (dielectric constant with no applied voltage) - (dielectric constant with an applied voltage) )/(dielectric constant with no applied voltage) .
  • tunability can be represented as T
  • X (dielectric constant with no applied voltage)
  • Y (dielectric constant with an applied voltage)
  • KV/c can range from 1-60% depending upon the composition of the materials employed.
  • the materials herein combine Barium Strontium Titanate (BaTiO--SrTiO_) with Magnesium Oxide (MgO) . These materials, encompassed by the present invention, are superior in that they are homogeneous, extremely dense, easily machinable, and possess superior electronic proper ⁇ ties at both dc and microwave operating frequencies. Moreover, the materials herein have low water absorptivity. Typically these materials will absorb less than 2% by weight of water therein. Hence, the materials within the scope of the present invention are environmentally stable - - for example, they have good moisture and temperature stability.
  • the present invention is the first teaching wherein BSTO is combined with magnesia in order to adjust the electronic properties and phase shifting ability of a material. Specifically, nowhere has BSTO been combined with magnesia to adjust the electronic properties of the material for use in a phase array antenna system. Aside from the combination of BSTO with magnesia being novel, its application in phase array antenna systems is an applica ⁇ tion never suggested in the prior art.
  • the present invention encompasses the fabrication of novel ceramic materials having enhanced electronic properties. These materials are superior to other currently employed ferroelectric materials.
  • Dielectric Constant Ideally the dielectric constant should be low, ranging from approximately 30 to 1,200. This dielectric constant range does not decrease the phase shifting ability of the material if a sufficient length of material is used (then a high dielectric constant is not needed). As insertion loss (loss of energy getting into the ceramic) does not depend upon the dielectric constant, it is not effected by lowering the dielectric constant. Also, since the loss tangent (tan S ) increases with increasing dielectric constant (for these ferroelec ⁇ tric materials) , lower dielectric constant materials tend to have lower loss tangents and therefore, less insertion loss.
  • the loss tangent (intrinsic to the material) serves to dissipate or absorb the incident micro ⁇ wave energy and therefore is most effective in this device when the loss tangent is in the range of 0.001 or less.
  • the low loss tangent serves to decrease the insertion loss and hence increase the phase shifter per decibel of loss.
  • the operating frequency is controlled by the loss tangent.
  • Extremely low loss materials (0.0007) can be used at millimeter wave range frequencies.
  • High Tunability The tunability of a particular material effects the material's electronic properties by how much the dielectric constant changes with applied voltage. The amount of phase shifting ability is directly related to the tunability; therefore, higher tunabilities are desired. The tunability can be increased to some extent by decreasing the sample thickness.
  • the insertion loss is inversely related to the tunability so that the larger the tunability, the smaller the insertion loss. Optimum electronic properties would have tunabilities ranging from 4 to 50% (depending upon other factors, dielectric constant and loss tangent) .
  • the materials within the scope of the present invention fall within the optimum characteristics outlined above. These materials are Ba, Sr TiO -MgO, wherein x is greater than 0.0 but less than or equal to 0.75.
  • This formulation may be referred to as Barium Strontium Titanate and magnesia.
  • the weight ratios of Barium Strontium Titanate (BSTO) to magnesia may range from 99% wt. - 40% wt. BSTO to 1% wt. - 60% wt. magnesia.
  • Magnesia is used herein to adjust the electronic properties of BSTO. Magnesia at low doping levels (1-10% wt.) lowers the Curie temperature (temperature at which the peak dielectric constant occurs) . At higher levels, it lowers the material's dielectric constant and loss to meet the requirements for various applications — for example, in the antenna arts.
  • the electronic properties of the formulation herein can be adjusted for use in any discrete element phase shifter design, such as planar microstrip, wave guide geometries or for use in a parallel plate structure.
  • the preparation of BSTO magnesia may be accomplished by obtaining powders of Barium Titanate and Strontium Titanate. These powders are ball milled in a conventional manner in an organic solvent. This particular mixture is then air-dried and calcined at approximately 200 degrees below the sintering temperature for several hours. The resultant BSTO is then mixed with magnesia in the desired weight percentage and re-ball milled in an organic solvent with a binder. The final mixture is then air-dried, once again, and dry-pressed at approximately 7,000 p.s.i. The final samples are sintered in air. Proper electroding of the composite ceramics must be done.
  • the samples were screen printed with a FERRO #3350 (Electronic Materials Division, Santa Barbara, California) silver conductive ink. They were subsequently fired at 450 for ten (10) minutes. The samples were then dipped in a bath of 2% silver (Ag) , 62% tin (Sn) and 36% lead (Pb) solder with lead clips attached.
  • FERRO #3350 Electro Materials Division, Santa Barbara, California
  • Table 1 sets forth the various properties of BSTO magnesia, wherein the formulation is represented by
  • the compositions with lower dielectric constants are probably likely to produce less impedance mismatch and may possess lower loss tangents.
  • EXAMPLE 1 Powder forms of Barium Titanate and Strontium Titanate were obtained from Ferro Corp., Transelco Division, Pen Yan, N.Y. (product nos. 219-6 and 218, respectively). The powders were stoichiometrically mixed in a slurry of ethanol and ball-milled using alumina 3/16" grinding media. This was performed for 24 hours. The mixture was subse ⁇ quently air dried and calcined for 5 hours at approximately 1100°C. The resulting BSTO was mixed with powder Magnesia (Johnson Malthey Electronics, Ward Hill, MA, product number 12287) in the proper weight percent. This mixture was then re-ball milled in a slurry of ethanol using a 3/16" alumina grinding media for an additional 24 hours.
  • Rhoplex B-60A (Rohm and Haas Co., Philadelphia, Pennsylvania), which is a 3% wt. organic binder consisting of an aqueous emulsion of acrylic polymer, was added to improve green body strength and to permit sample fabrication in greater dimensions.
  • Green body strength refers to the ability of unfired material to remain intact and to withstand handling; it also implies better densities in the unfired pieces.
  • Other binders and plasticizers may be added at this point to allow extrusion molding or for fabrication of tape-cast sheets of material.
  • the mixture is then air-dried and dry-pressed to a pressure of approximately 7,000 p.s.i.
  • Sintering schedules are ascertained by employing a deflectometer such as a Mitutoyo digimatic indicator and miniprocessor (Mitutoyo Corp., Paramus, N.J.).
  • the final samples were fired in various furnaces and the densities of the samples were found to be reproducible to within 1 to 2%.
  • BSTO - Magnesia samples are set forth in Table 1, above. While particular embodiments of the present invention have been shown and described, it will be obvious to those skilled in the art that changes and modifications may be made without departing from this invention.
  • the invention may be modified to include ceramic-ceramic composites of BSTO and other low dielectric constant materials depending upon the particular requirements of the intended application.
  • the other low dielectric constant materials which may be combined with BSTO are zirconia, alumina microballoons, alumina fibers or fabric, silicon dioxide and other low dielectric constant, low dielectric loss oxides.
  • Alumina microballoons are hollow spheres of approximately 1-5 microns in diameter and are already sintered components (BSTO/ceramic) — the electronic properties of a composite employing alumina microballoons will most likely differ from composites employing alumina powder.
  • Alumina fibers or fabric when employed in the composite within the scope of the present invention, may possess electronic properties different from composites which employ alumina powder. This is due to the fact that this form of alumina is most likely to be in sintered form; and the fibers or fabric alumina produce different connectivity between the BSTO particles.) It is, therefore, intended that the claims herein are to include all such obvious changes and modifications as fall within the true spirit and scope of this invention.

Landscapes

  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Ceramic Engineering (AREA)
  • Manufacturing & Machinery (AREA)
  • Materials Engineering (AREA)
  • Structural Engineering (AREA)
  • Organic Chemistry (AREA)
  • Inorganic Insulating Materials (AREA)
  • Compositions Of Oxide Ceramics (AREA)

Abstract

Nouveaux matériaux céramiques ferroélectriques présentant une faible constante diélectrique, de très faibles pertes et une accordabilité élevée. Il s'agit de composites de titanate de baryum/strontium (BSTO) et d'un matériau céramique à faible constante diélectrique. Le composite préféré est du type Ba1-xSrxTiO3-MgO où x est compris entre 0,00 et 0,75, et où les proportions en poids de Ba1-xSrxTiO3 et de MgO sont respectivement comprises entre 99 et 40 % et 1 et 60 %. Ces nouveaux matériaux aux excellentes propriétés électroniques peuvent s'utiliser dans différents systèmes d'antennes pour longueurs d'ondes micrométriques et millimétriques.
EP94920023A 1993-06-09 1994-05-24 NOUVEAU MATERIAU COMPOSITE CERAMIQUE FERROELECTRIQUE A BASE DE BSTO/MgO Withdrawn EP0705230A4 (fr)

Applications Claiming Priority (5)

Application Number Priority Date Filing Date Title
US76291 1993-06-09
US08/076,291 US5312790A (en) 1993-06-09 1993-06-09 Ceramic ferroelectric material
US08/207,446 US5427988A (en) 1993-06-09 1994-03-07 Ceramic ferroelectric composite material - BSTO-MgO
US207446 1994-03-07
PCT/US1994/005649 WO1994029236A1 (fr) 1993-06-09 1994-05-24 NOUVEAU MATERIAU COMPOSITE CERAMIQUE FERROELECTRIQUE A BASE DE BSTO/MgO

Publications (2)

Publication Number Publication Date
EP0705230A1 true EP0705230A1 (fr) 1996-04-10
EP0705230A4 EP0705230A4 (fr) 1996-07-17

Family

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Family Applications (1)

Application Number Title Priority Date Filing Date
EP94920023A Withdrawn EP0705230A4 (fr) 1993-06-09 1994-05-24 NOUVEAU MATERIAU COMPOSITE CERAMIQUE FERROELECTRIQUE A BASE DE BSTO/MgO

Country Status (5)

Country Link
EP (1) EP0705230A4 (fr)
JP (1) JPH08511502A (fr)
AU (1) AU7095194A (fr)
CA (1) CA2164594A1 (fr)
WO (1) WO1994029236A1 (fr)

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR101018291B1 (ko) * 2009-03-18 2011-03-04 한국과학기술연구원 강유전체 박막 및 산화물이 첨가된 강유전체 박막을 포함하는 적층 구조체 및 그 제조 방법
CN101870581A (zh) * 2010-06-25 2010-10-27 华中科技大学 一种制备Ba1-xSrxTiO3-MgO铁电陶瓷坯体的方法
CN112174198A (zh) * 2020-09-30 2021-01-05 湖南先导电子陶瓷科技产业园发展有限公司 一种高纯超细纳米钛酸锶钡材料的合成方法

Family Cites Families (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS6386319A (ja) * 1986-09-30 1988-04-16 太陽誘電株式会社 誘電体磁器組成物
JPH0821266B2 (ja) * 1987-03-11 1996-03-04 株式会社村田製作所 誘電体ペ−スト
JPH0692268B2 (ja) * 1988-06-03 1994-11-16 日本油脂株式会社 還元再酸化型半導体セラミックコンデンサ素子
JPH038765A (ja) * 1989-06-06 1991-01-16 Matsushita Electric Ind Co Ltd 電圧依存性非直線抵抗体磁器組成物およびバリスタの製造方法
DE4200356C2 (de) * 1991-01-11 2000-05-18 Murata Manufacturing Co Verfahren zur Herstellung einer nicht-reduzierbaren dielektrischen keramischen Zusammensetzung
JP2761690B2 (ja) * 1992-02-04 1998-06-04 太陽誘電株式会社 磁器コンデンサ及びその製造方法

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
DATABASE WPI Week 9339 Derwent Publications Ltd., London, GB; AN 93-306543 XP002000889 & JP-A-05 217 795 (TAIYO YUDEN) , 27 August 1993 *
See also references of WO9429236A1 *

Also Published As

Publication number Publication date
EP0705230A4 (fr) 1996-07-17
CA2164594A1 (fr) 1994-12-22
WO1994029236A1 (fr) 1994-12-22
AU7095194A (en) 1995-01-03
JPH08511502A (ja) 1996-12-03

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