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EP0994823A1 - Procede de preparation de composes de titanate zirconate de plomb - Google Patents

Procede de preparation de composes de titanate zirconate de plomb

Info

Publication number
EP0994823A1
EP0994823A1 EP98932376A EP98932376A EP0994823A1 EP 0994823 A1 EP0994823 A1 EP 0994823A1 EP 98932376 A EP98932376 A EP 98932376A EP 98932376 A EP98932376 A EP 98932376A EP 0994823 A1 EP0994823 A1 EP 0994823A1
Authority
EP
European Patent Office
Prior art keywords
aqueous solution
salt
combining
lead
precipitate
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Withdrawn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
EP98932376A
Other languages
German (de)
English (en)
Inventor
Ian Davidson Marshall
David Henry Bennett
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.)
UK Secretary of State for Defence
Original Assignee
UK Secretary of State for Defence
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
Application filed by UK Secretary of State for Defence filed Critical UK Secretary of State for Defence
Publication of EP0994823A1 publication Critical patent/EP0994823A1/fr
Withdrawn legal-status Critical Current

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
    • C01G25/00—Compounds of zirconium
    • C01G25/006—Compounds containing zirconium, with or without oxygen or hydrogen, and containing two or more other elements
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2002/00—Crystal-structural characteristics
    • C01P2002/30—Three-dimensional structures
    • C01P2002/34—Three-dimensional structures perovskite-type (ABO3)

Definitions

  • This invention relates to a process for the preparation of lead zirconate titanate compounds. More specifically this invention relates to a process for the preparation of lead zirconate titanate compounds which are doped with either niobia, or niobia and stannic oxide.
  • PZT Lead zirconate titanate
  • D, M are dopants and at least one of a,b are none zero.
  • Common dopants, used for PZT compounds include donor additives such as Nb 5+ , acceptor additives such as Fe 3+ , and isovalent additives such as Sn 4+ .
  • PZT compounds are ceramic materials that, when poled, exhibit valuable piezoelectric and electrooptic properties; they are commonly used for capacitor and piezoelectric transducer applications.
  • a number of processes have been developed for the synthesis of lead zirconate titanate compounds.
  • the choice of a process depends upon a number of factors, including the purity, homogeneity, and yield of the product required.
  • the process chosen may also depend upon scale of the process required; safety and waste disposal being particularly important factors for large scale syntheses.
  • lead zirconate titanate compounds have been synthesised by mixing metal oxide powders, followed by calcination and sintering of the mixture. Such processes usually call for high sintering temperatures and can adversely affect the properties of the product.
  • More recently lead zirconate titanate compounds have been synthesised from a mixture of appropriate metal alkoxides, as described in Japanese Laid-Open patent application No. 86022/85.
  • metal alkoxides can result in traces of carbon in the product, having an adverse effect upon the product quality.
  • metal alkoxides are inflammable and hydrophilic, and the use of these precursors can result in processing and safety problems for large scale syntheses of lead zirconate titanate compounds.
  • the presence of carbon impurities can result in reduction of the lead component of lead zirconate titanate compounds to free lead. It is therefore desirable to reduce residual carbon content in the product by minimising the use of organic precursors, and by minimising the use of organic solvents such as alcohols. Co-precipitation processes have been developed that minimise the use of organic precursors.
  • co- precipitation processes involve the addition of oxalic acid to an aqueous solution of metal ions to produce a oxalate precipitate.
  • Ammonia usually in the form of an aqueous solution, is often used to reduce the solubility of the oxalate precipitate in the mother liquor.
  • the oxalate precipitate is then filtered, washed and calcined to generate the lead zirconate titanate compound.
  • TiC is one source of titanium that can be used in such co-precipitation processes, though this source can lead to undesirable chloride impurities in the product.
  • a further problem with the co-precipitation processes is the solubility of the oxalate precipitate in the mother liquor, which can reduce yields.
  • EP 280033 Bl describes a co-precipitation process that involves the use of ethanol or other alcohols to reduce the solubility of the mixed oxalate.
  • the source of the titanium ions for the process disclosed in EP 280033 B 1 is titanium isopropoxide.
  • the titanium isopropoxide is reacted with water to yield a titanium hydroxide precipitate.
  • the titanium hydroxide precipitate is then filtered off, washed, and then dissolved in concentrated nitric acid.
  • the EP 280033 Bl method requires a relatively large amount of concentrated nitric acid and this has an adverse effect upon the product quality and yield.
  • a process for producing a lead zirconate titanate compound which comprises the following steps:
  • step (b) combining the products from step (a) with concentrated nitric acid;
  • step (c) combining the products from step (b) with an aqueous solution of a zirconium salt;
  • step (d) combining the products from step (c) with an excess of oxalic acid to produce a mixture that includes an oxalate precipitate, and adjusting the pH of the solution containing the oxalate precipitate with ammonia or an amine until the pH is between 8.5 and 9.5; and
  • An advantage of this process is that a relatively small amount of concentrated nitric acid is required to dissolve the titanium hydroxide, which is produced when the alkoxide is combined with the water.
  • the small amount of concentrated nitric acid results in improved product quality and yield. Only a relatively small amount of concentrated nitric acid is required because the titanium alkoxide is combined with water in the presence of the lead salt.
  • a further advantage of this process is that the titanium hydroxide does not need to be filtered off before the addition of the concentrated nitric acid.
  • a yet further advantage of this process is that no ethanol or other alcohol is required to reduce the solubility of the mixed oxalate, though such use is not precluded.
  • step (c) comprises the following steps:
  • step (i) combining the products from step (b) with an aqueous solution of a zirconium salt;
  • step (ii) combining the products from step (i) with an aqueous solution of a niobium salt.
  • this process is used as a means for producing a lead zirconate titanate compound characterised in that the aqueous solution of the niobium salt is an aqueous solution of hydrated niobium oxide. More advantageously this process is characterised in that the aqueous solution of the hydrated niobium oxide is prepared by a process that comprises the steps:
  • step (ii) combining the precipitate produced in step (i) with an aqueous solution of oxalic acid.
  • the titanium alkoxide is a titanium propoxide. More preferably the titanium alkoxide is titanium n-propoxide.
  • the optimum choice of titanium alkoxide depends upon a number of factors.
  • the alkoxide should have a relatively small carbon content to reduce carbon impurities in the lead zirconate titanate compond. However, the carbon content should not be so small as to make the alkoxide too reactive.
  • Example 1 The present invention will now be described by way of example only.
  • Example 1 The present invention will now be described by way of example only.
  • aqueous solution of zirconium nitrate hydrate is prepared by dissolving commercially available concentrated nitric acid (10 ml) in deionised water (2 litre); commercially available white grade zirconyl nitrate hydrate (1100 g) is then dissolved in this nitric acid solution. The resulting solution is then heated to aid dissolution and further deionised water is added until the total volume is 3 litres. Once any particulate has been minimised, by heating and stirring, the particulate matter is allowed to settle and the aqueous solution of zirconium nitrate hydrate is siphoned off. This method can also be used to prepare other aqueous solutions of zirconium salts.
  • An aqueous solution of ammonia is prepared by combining analar grade 25% aqueous ammonia solution (200 ml) and deionised water (200 ml).
  • the aqueous solution of ammoma is combined with niobium pentachloride (99% purity), resulting in the formation of a hydrated niobium oxide precipitate.
  • the supernatant liquid is siphoned off once the hydrated niobium oxide precipitate has settled out.
  • the precipitate is then vacuum filter washed with deionised water using a Watman No. 541 filter paper, until the conductivity of the filtrate is less than 0.2 mS and is then filter dried.
  • An aqueous solution of oxalic acid is prepared by dissolving analar grade hydrated oxalic acid (336 g) in deionised water (3 litres). The dried precipitate is then added to this aqueous solution of oxalic acid. The resulting aqueous solution of hydrated niobium oxide is then vacuum filtered using Whatman No. 542 filter paper. This method can also be used to prepare other aqueous solutions of niobium salts.
  • analar grade lead nitrate (717.00g) is dissolved in 3.55 litres of deionised water. This aqueous solution of lead nitrate is then added to commercially available titanium n-propoxide (28.94g) to produce a suspension of hydrated titanium oxide. 30 minutes after the addition of the lead nitrate solution, concentrated Analar grade nitric acid (10 ml) is added to dissolve the hydrated titamum oxide. This addition of concentrated nitric acid (10ml) is repeated a further five times, with stirring, each addition being separated by a ten minute interval.
  • a second solution of oxalic acid is prepared by dissolving analar grade oxalic acid dihydrate (914.93g) in deionised water (9.76 litre).
  • a portion (2294g) of the aqueous solution of zirconium nitrate hydrate prepared above, is then added to the solution containing lead and titanium ions.
  • a portion (470.45g) of the aqueous solution of hydrated niobium oxide prepared above is added and the resulting solution is stirred for 1 hour.
  • the solution of lead, zirconium, titamum and niobium ions is then added to an excess of oxalic acid and the oxalate precipitate, thus produced, is stirred for 1 hour.
  • the excess of oxalic acid is in the form of the second solution of oxalic acid prepared above and is approximately 1.1 times that amount required to convert all the metal ions to the corresponding oxalates.
  • 25% aqueous ammonia (approximately 2.5 litres) is then added to the solution containing the oxalate precipitate, with continuous stirring over a period of 2.5 hours.
  • the temperature is controlled by controlling the rate of addition of the aqueous ammonia; and should not be allowed to exceed 40°C.
  • the addition of the ammoma is stopped once the pH of the solution reaches 9, but stirring continues for 2 hours after the ammonia addition has ceased.
  • the supernate is siphoned off and the residual slurry is filtered through a buchner funnel fitted with a Whatman No. 3 filter paper.
  • the oxalate precipitate is then vacuum filter washed with deionised water until the conductivity of the filtrate is less than 3 mS.
  • the precipitate Once the precipitate has been washed it is air dried, however, it should not be allowed to dry out or crack during the washing process.
  • the air dried precipitate is mixed with 4.5 litres of deionised water and the resulting slurry is spay dried.
  • the dried oxalate precipitate is then calcined using the following shedule: (i) 30°C/hour to 300°C for a dwell of 1 hour, (ii) 10°C/hour to 400°C for a dwell of 1 hour, (iii) 60°C/hour to 600°C for a dwell of 2 hours, (iv) 60°C/hour to 775°C for a dwell of 16 hours. This is followed by natural cooling down to ambient temperature, to yield a lead zirconate titnate compound having niobia as a dopant.
  • the compound has the formula: Pbo. 9 ⁇ (Zro.9 5 Tio.o 5 )o.
  • a first solution prepared by combining analar grade 25% aqueous ammoma solution (250ml) and deionised water (800 ml) is added to a second solution, prepared by adding GPR grade tin (IV) chloride (200 g) to deionised water (600 ml).
  • GPR grade tin (IV) chloride 200 g
  • the resulting mixture which includes a precipitate, is stirred for thirty minutes and is left to stand.
  • the precipitate is vacuum filter washed with deionised water using a buchner funnel fitted Whatman No. 541 filter paper. The precipitate is then vacuum dried until it is dry enough to remove from the filter paper.
  • This semi-dry precipitate is dissolved in an aqueous solution of oxalic acid, prepared by dissolving analar grade hydrated oxalic acid (200 g) in deionised water (1.944 litres). Once the precipitate has completely dissolved, a process that may take several days, the solution is vacuum filtered using a Whatman no. 542 filter paper / 0.2 micron cellulose nitrate membrane filter. The filtered solution is a tin stock solution used in the subsequent steps of the process.
  • analar grade lead nitrate (710.00g) is dissolved in 3.52 litres of deionised water. This aqueous solution of lead nitrate is then added to commercially available titamum n-propoxide (28.9228g) to produce a suspension of hydrated titanium oxide. 30 minutes after the addition of the lead nitrate solution, concentrated Analar grade nitric acid (10 ml) is added, to dissolve the hydrated titanium oxide precipitate. This addition of concentrated nitric acid (10ml) is repeated a further five times, with stirring, each addition being separated by a ten minute interval.
  • a first solution of oxalic acid is prepared by dissolving analar grade oxalic acid dihydrate (892g) in deionised water (9.84 litre).
  • a portion (317.9643 g) of the aqueous solution of hydrated niobium oxide, prepared in example 1 is added and the resulting solution is stirred for 1 hour.
  • a portion (433g) of the tin stock solution is added to the first solution of oxalic acid (9.84 litre), which was prepared while the hydrated tianium oxide was dissolving, to produce a second solution of oxalic acid.
  • the solution of lead, zirconium, titamum and niobium ions is then added to the second solution of oxalic acid, and the oxalate precipitate thus produced is stirred for 1 hour.
  • An excess of oxalic acid is used to produce the oxalate and the excess is in the form of the second solution of oxalic acid. The excess is approximately 1.1 times that amount required to convert the metal ions to the corresponding oxalates.
  • 25% aqueous ammonia (approximately 2.5 litres) is then added to the solution containing the oxalate precipitate, with continuous stirring over a period of 2.5 hours.
  • the temperature is controlled by controlling the rate of addition of the aqueous ammonia; the temperature should not be allowed to exceed 40°C.
  • the addition of the ammonia is stopped once the pH of the solution reaches 9, but the mixture continues to be stirred for 2 hours after the ammonia addition has ceased.
  • the supernate is siphoned off and the residual slurry is filtered through a buchner funnel fitted with a Whatman No. 3 filter paper.
  • the precipitate is then vacuum filter washed with deionised water until the conductivity of the filtrate is less than 3 mS.
  • the precipitate Once the precipitate has been washed it is air dried, however, it should not be allowed to dry out or crack during the washing process.
  • the air dried precipitate is mixed with 4.5 litres of deionised water and the resulting slurry is spray dried.
  • the dried oxalate is then calcined using the same schedule as described in example 1 followed by natural cooling down to ambient temperature, to yield lead zirconate titanate compound having niobia as a first dopant and stannic oxide as a second dopant.
  • the compound has the formula:
  • This method is also suitable for the preparation of other lead zirconate titanate compounds, for example compounds having the formula Pb x Zr y Ti z D a M b O 3 where D, M are dopants and at least one of a,b are none zero.

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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Inorganic Chemistry (AREA)
  • Inorganic Compounds Of Heavy Metals (AREA)

Abstract

L'invention concerne un procédé permettant de produire un composé de titanate zirconate de plomb et consistant à combiner une solution aqueuse d'un sel de plomb à un composé alcoxyde de titane, puis à ajouter de l'acide nitrique concentré, une solution aqueuse d'un sel de zirconium et un excédent d'acide oxalique et ce, dans le but de produire un oxalate. Le pH de la solution renfermant cet oxalate est régulé grâce à l'utilisation d'ammoniaque ou d'une amine, avant que l'oxalate ne soit calciné et ce, dans le but de former le composé de titanate zirconate de plomb.
EP98932376A 1997-07-05 1998-07-03 Procede de preparation de composes de titanate zirconate de plomb Withdrawn EP0994823A1 (fr)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
GB9714150 1997-07-05
GBGB9714150.1A GB9714150D0 (en) 1997-07-05 1997-07-05 Process for the preparation of lead zirconate titanate compounds
PCT/GB1998/001979 WO1999001379A1 (fr) 1997-07-05 1998-07-03 Procede de preparation de composes de titanate zirconate de plomb

Publications (1)

Publication Number Publication Date
EP0994823A1 true EP0994823A1 (fr) 2000-04-26

Family

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EP98932376A Withdrawn EP0994823A1 (fr) 1997-07-05 1998-07-03 Procede de preparation de composes de titanate zirconate de plomb

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EP (1) EP0994823A1 (fr)
GB (1) GB9714150D0 (fr)
WO (1) WO1999001379A1 (fr)

Families Citing this family (1)

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Publication number Priority date Publication date Assignee Title
ES2187320B1 (es) * 2000-07-20 2004-09-16 Jesus Consejo Superior De Investigaciones Cientificas Peptido cationico anfipatico y su aplicacion en vectores de transferencia genica.

Family Cites Families (5)

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Publication number Priority date Publication date Assignee Title
JPS6355118A (ja) * 1986-08-22 1988-03-09 Natl Inst For Res In Inorg Mater Ｐｌｚｔ透明焼結体の製造法
JPH07115873B2 (ja) * 1986-11-26 1995-12-13 日本セメント株式会社 圧電性酸化物微粉末の製造方法
JPS63156057A (ja) * 1986-12-19 1988-06-29 科学技術庁無機材質研究所長 高密度ペロブスカイトセラミックスの製造法
JPH01294529A (ja) * 1988-05-20 1989-11-28 Mitsubishi Petrochem Co Ltd Ａｂｏ↓３型ペロブスカイト型酸化物の製造方法
JPH0656425A (ja) * 1992-07-31 1994-03-01 Nok Corp Ｐｌｚｔ粉体の製造方法

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO9901379A1 *

Also Published As

Publication number Publication date
WO1999001379A1 (fr) 1999-01-14
GB9714150D0 (en) 1997-09-10

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