EP1532084A1 - Keramik mit perovskit-struktur, dessen verwendung als referenzelektrode - Google Patents

Keramik mit perovskit-struktur, dessen verwendung als referenzelektrode

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Publication number
EP1532084A1
EP1532084A1 EP03758261A EP03758261A EP1532084A1 EP 1532084 A1 EP1532084 A1 EP 1532084A1 EP 03758261 A EP03758261 A EP 03758261A EP 03758261 A EP03758261 A EP 03758261A EP 1532084 A1 EP1532084 A1 EP 1532084A1
Authority
EP
European Patent Office
Prior art keywords
ceramic
electrode
powder
grains
chosen
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Withdrawn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
EP03758261A
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English (en)
French (fr)
Inventor
Claude Bohnke
Odile Bohnke
Jean-Louis Fourquet
Huguette Duroy
André LEBLE
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.)
Centre National de la Recherche Scientifique CNRS
Le Mans Universite
University of Maine System
Original Assignee
Centre National de la Recherche Scientifique CNRS
Le Mans Universite
University of Maine System
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Filing date
Publication date
Application filed by Centre National de la Recherche Scientifique CNRS, Le Mans Universite, University of Maine System filed Critical Centre National de la Recherche Scientifique CNRS
Publication of EP1532084A1 publication Critical patent/EP1532084A1/de
Withdrawn legal-status Critical Current

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    • 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
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
    • B01D71/02—Inorganic material
    • B01D71/024—Oxides
    • B01D71/0271—Perovskites
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    • C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/622—Forming processes; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/626—Preparing or treating the powders individually or as batches ; preparing or treating macroscopic reinforcing agents for ceramic products, e.g. fibres; mechanical aspects section B
    • C04B35/62605—Treating the starting powders individually or as mixtures
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    • C04B35/626—Preparing or treating the powders individually or as batches ; preparing or treating macroscopic reinforcing agents for ceramic products, e.g. fibres; mechanical aspects section B
    • C04B35/62605—Treating the starting powders individually or as mixtures
    • C04B35/62625—Wet mixtures
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
    • G01N27/26—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrochemical variables; by using electrolysis or electrophoresis
    • G01N27/28—Electrolytic cell components
    • G01N27/30—Electrodes, e.g. test electrodes; Half-cells
    • G01N27/301—Reference electrodes
    • H—ELECTRICITY
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    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
    • H01M4/8636—Inert electrodes with catalytic activity, e.g. for fuel cells with a gradient in another property than porosity
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
    • H01M4/88—Processes of manufacture
    • H01M4/8878—Treatment steps after deposition of the catalytic active composition or after shaping of the electrode being free-standing body
    • H01M4/8896—Pressing, rolling, calendering
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
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    • C04B2235/30—Constituents and secondary phases not being of a fibrous nature
    • C04B2235/32—Metal oxides, mixed metal oxides, or oxide-forming salts thereof, e.g. carbonates, nitrates, (oxy)hydroxides, chlorides
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    • C04B2235/32—Metal oxides, mixed metal oxides, or oxide-forming salts thereof, e.g. carbonates, nitrates, (oxy)hydroxides, chlorides
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    • C04B2235/32—Metal oxides, mixed metal oxides, or oxide-forming salts thereof, e.g. carbonates, nitrates, (oxy)hydroxides, chlorides
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    • C04B2235/32—Metal oxides, mixed metal oxides, or oxide-forming salts thereof, e.g. carbonates, nitrates, (oxy)hydroxides, chlorides
    • C04B2235/3231—Refractory metal oxides, their mixed metal oxides, or oxide-forming salts thereof
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    • C04B2235/54—Particle size related information
    • C04B2235/5418—Particle size related information expressed by the size of the particles or aggregates thereof
    • C04B2235/5436—Particle size related information expressed by the size of the particles or aggregates thereof micrometer sized, i.e. from 1 to 100 micron
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    • C04B2235/70—Aspects relating to sintered or melt-casted ceramic products
    • C04B2235/74—Physical characteristics
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    • C04B2235/768—Perovskite structure ABO3
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    • C04B2235/78—Grain sizes and shapes, product microstructures, e.g. acicular grains, equiaxed grains, platelet-structures
    • C04B2235/786—Micrometer sized grains, i.e. from 1 to 100 micron
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
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    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/30—Hydrogen technology
    • Y02E60/50—Fuel cells

Definitions

  • Ceramic with perovskite structure its use as a reference electrode
  • the present invention relates to a ceramic with a perovskite structure, as well as its use as a reference electrode in a pH measuring device.
  • a frequently used measurement electrode is an electrode called glass electrode, constituted by the electrochemical chain Ag / AgCl / internal solution at pH 7 / glass. [Cf. F. Haber, Z. Klemencewitz, Z. Phys. Chem. 67 (1909) 385].
  • Electrodes for measuring pH are based on redox reactions involving protons. It is, for example, an antimony oxide electrode usable for industrial or food environments, which is based on the reaction
  • These measurement electrodes are generally associated with internal reference electrodes of the M / MX / X "type in aqueous solution, M being a metal and MX a poorly soluble compound of said metal, for example an oxide or a halide other than a fluoride.
  • a particularly preferred internal reference electrode is of the Pt / Hg / Hg 2 Cl 2 type .
  • the glass reference electrodes In the presence of such internal reference electrodes, the glass reference electrodes have some disadvantages In order to keep the concentration of halide ions constant or hydroxides, it is necessary to use saturated or very concentrated solutions. Because a sintered glass allows electrolytic continuity between the reference electrode and the measurement solution, it is necessary to periodically readjust the concentration of the solution, due to the diffusion of the ions from the saturated or concentrated solution to the measurement solution. In addition, when the measuring devices are used in viscous media or highly concentrated in proteins (for example in dairy products), the sintered glass becomes clogged, which leads to a discontinuity in the electrolytic measuring chain.
  • Perovskites are also known and their use for the development of electrodes, in particular in batteries.
  • the present inventors have now found that the method of preparation of perovskites could have an important influence on their properties and that, depending on the properties, perovskites had different applications.
  • the aim of the present invention is to provide a ceramic with a perovskite structure having a particular structure which makes it insensitive to variations in pH in a medium, a method for preparing it, and a reference electrode comprising said ceramic as active element, usable in particular in a pH measuring device.
  • a ceramic according to the present invention is characterized in that it has a perovskite structure and that it has the following properties: its composition corresponds to the formula L (2/3 ) - x A 3x ( ⁇ / 3) - 2 ⁇ E0 3 , in which:
  • L represents at least one element chosen from Sb, Bi, lanthanides and non-toxic and non-radioactive alkaline earth metals;
  • A represents at least one element chosen from Ag and alkali metals
  • * E represents a transition metal which can be oxidized up to the +5 oxidation state, alone or associated with at least one other element chosen from Al and the transition metals which can be oxidized up to the +5 or +6 oxidation state; * represents a gap; * 0.03 ⁇ x ⁇ 0.16; it consists of grains having a dimension of the order of 3 to 5 ⁇ m, said grains having an irregular parallelepipedic structure or an irregular octahedral structure; - it has a specific surface of the order of 2,000 to 4,000 cm 2 / g.
  • L is a lanthanide chosen from La, Nd, Sm or Pr, an alkaline earth metal chosen from Mg, Sr, Ba and Ca, or bismuth
  • A represents at least element chosen from Li, Na and Ag
  • E represents a transition metal chosen from Ti, V, Ta and Nb, possibly associated with Mo or W.
  • Specific examples are constituted by the ceramics corresponding to one of the formulas La (2 3) - x Li 3x ( ⁇ / 3 ) - 2 ⁇ Ti0 3 or Nd (2/3) - x Li 3x ( ⁇ / 3) - 2x Ti0 3 .
  • a ceramic according to the present invention can be obtained by a method consisting in sintering an initial powder of a ceramic having the composition
  • L (2/3 ) - ⁇ A 3x ( ⁇ / 3 ) - 2 ⁇ E0 3 in which L, A, and E have the meaning given above.
  • the method is characterized in that: an initial ceramic powder is used, at least 50% of the grains of which have a dimension greater than 18 ⁇ m; the powder is compacted under a pressure of 251 to 500 Mpa; the compacted powder is subjected to sintering at a temperature between 1050 and 1350 ° C.
  • a unidirectional press or an isostatic press can be used for the compacting step of the ground powder. Compaction is almost immediate.
  • the compacted powder is brought to the sintering temperature, preferably at a speed of 20-30 ° C / min.
  • the sintering time is advantageously between 5 and 12 hours. A duration of 10 hours is generally suitable.
  • the initial powder is obtained by subjecting a coarse-grained powder of a ceramic having the desired composition to low-energy grinding, for example in a mortar grinder of the "RM 100" type sold by the Retsch company.
  • a ceramic according to the present invention is insensitive to the variation in pH when it is used as an active element of an electrode. This is why another object of the present invention consists of an electrode insensitive to the variation in pH, usable as a reference electrode.
  • a reference electrode according to the present invention comprises a ceramic according to the invention as a sensitive element. It can be of the membrane type, or of the all-solid type.
  • a membrane type electrode comprises a tube closed at its lower part by a ceramic membrane according to the invention.
  • the tube is made of a material having good mechanical strength and chemical inertness with respect to the medium whose pH is sought to be determined.
  • the tube contains a buffer solution, into which an internal electrode, for example of the M / MX / X " type, is immersed in aqueous solution, M being a metal and MX a poorly soluble compound of said metal, for example an oxide or a halide other than
  • a particularly preferred internal reference electrode is of the Pt / Hg / Hg 2 Cl 2 type .
  • An electrode of the "all solid” type consists of the metal / ceramic electrochemical chain, the ceramic being a ceramic according to the invention. Contact between the metal and the ceramic can be obtained by bonding or by any other means, in particular by vacuum deposition of the metal on the ceramic.
  • the metal is chosen from Ag or a transition metal.
  • a pH measurement device comprises a reference electrode insensitive to variations in pH and a measurement electrode having a high sensitivity to such variations in a medium, the two electrodes being connected by a millivoltmeter with high input impedance.
  • An electrode according to the present invention is particularly well suited for use as a reference electrode in such a device.
  • FIG. 1 represents the diagram of a pH measuring device in which the reference electrode has the "membrane" configuration.
  • This device comprises a reference electrode according to the invention (1), a measurement electrode (2), a millivoltmeter (3) with high input impedance (for example of the MINISIS 8000 type sold by the company Tacussel, or of the type pHm210 marketed by the company Radiometer), a device (4) for signal processing (for example an Agilent acquisition center).
  • the two electrodes are immersed in the same thermostated solution, not shown, for which it is desired to determine the pH.
  • the measuring electrode (2) can be of the commercially available "glass electrode” type.
  • the reference electrode (1) comprises a tube (5) closed at its lower part by a ceramic membrane (6) according to the invention.
  • the tube contains a buffer solution (7) constituted for example by an aqueous solution saturated with KC1 and having a pH kept constant during the measurement (for example a saturated solution with KCl at pH 1).
  • An electrode internal reference (8) immersed in the buffer solution (7).
  • the internal reference electrode (8) can be of the Pt / Hg / Hg 2 Cl 2 type .
  • the measuring electrode (2) is connected directly to the millivoltmeter (3).
  • the reference electrode (1) is connected to the millivoltmeter via the internal reference electrode (8).
  • FIG. 2 represents the diagram of a pH measurement device in which the reference electrode is of the "all solid” type constructed along the "metal / ceramic” electrochemical chain.
  • This device comprises a reference electrode according to the invention (1 ′), a measurement electrode
  • the reference electrode consists of a tube closed at its lower part by a ceramic pellet (6 ') according to the invention, a wire (9) of transition metal fixed to the ceramic by an adhesive (10) and connected with a millivoltmeter (3 ').
  • an electrode comprising a ceramic according to the invention as a reference electrode has many advantages. Materials of the ceramic type do not present any danger in food or the environment. They have high thermal stability, up to 600 ° C. The cost of manufacturing the material itself and the electrodes, as well as maintaining the electrodes is low.
  • a reference electrode according to the invention is associated, in a pH measurement device, with a measurement electrode whose sensitive element is a ceramic with a perovskite structure which may have a chemical composition similar to that of the active element of the present reference electrode, but whose structure and specific surface are different.
  • Such a measuring electrode can be constructed in the form of a membrane electrode or in the form "all solid ", in the same way as the reference electrode according to the invention.
  • the ceramic forming the membrane of the measurement electrode has a perovskite structure and it has the following properties: - its composition corresponds to the formula
  • L represents at least one element chosen from Sb, Bi, lanthanides and non-toxic and non-radioactive alkaline earth metals
  • A represents at least one element chosen from Ag and alkali metals
  • E ' represents a transition metal which can be oxidized to the oxidation state +5, alone or associated with at least one other element chosen from Al and the transition metals which can be oxidized to the state +5 or +6 oxidation;
  • Such a ceramic can be obtained by a process consisting in preparing an initial powder of a ceramic having the composition L '( 2/3 ) - ⁇ A' 3x ( ⁇ / 3 ) - 2 ⁇ E'0 3 and of which at least 50% grains have a size of less than 5 ⁇ m, compact the powder under a pressure of 251 to 740 Mpa, then subject the compacted powder to sintering at a temperature between 1050 and 1350 ° C.
  • the pH measurement devices in which the reference electrode according to the invention is in the "all solid" configuration is particularly advantageous in environments requiring temperatures and / or high pressures, which is common in the food industry. Particular preference will be given to devices in which the measurement electrode is also an electrode in the "all solid” configuration having a ceramic as an active element.
  • the present invention is described in more detail below, with reference to the following examples which are given by way of illustration, but to which the invention is not limited.
  • the specific surface and the grain size distribution of the different ceramic powders were determined using an LS laser granulometer from the company Coulter.
  • the particle size distribution is given in tables in which the percentage of particles indicated in a column corresponds to the percentage of grains having a size less than the value indicated in the 2nd row of the same column.
  • This powder was obtained by grinding a coarse-grained ceramic powder in a Retsch RM100 mortar mill for a period of 10 min. It is noted that 50% of the grains have a dimension less than 18.25 ⁇ m.
  • Said powder was subjected to compaction under a pressure of 251 Mpa.
  • the compacted pellet formed was heated to raise its temperature from 25 ° C per min, to 1300 ° C and this temperature was maintained for 10 hours.
  • FIG. 3 represents a photograph (magnification ⁇ 3000) with a Hitachi 2300 electron microscope of the sintered pellet obtained.
  • the presence of poorly crystallized grains is noted, the size of which is of the order of 3 ⁇ m for the smallest and 5 ⁇ m for the largest. We observe the presence of gaps between the grains.
  • This powder was obtained by grinding a coarse-grained ceramic powder in a Retsch mortar grinder RM100 for a period of 10 minutes It is noted that 50% of the grains have a size less than 18.25 ⁇ m.
  • Said powder was subjected to compaction under a pressure of 251 Mpa.
  • the compacted pellet formed was heated to raise its temperature from 25 ° C per min, to 1150 ° C and this temperature was maintained for 10 hours.
  • FIG. 4 represents a photograph (magnification ⁇ 3000) with a Hitachi 2300 electron microscope of the sintered pellet obtained. The presence of poorly crystallized grains is noted, the size of which is of the order of 3 ⁇ m for the smallest and 5 ⁇ m for the largest. We observe the presence of gaps between the grains.
  • Example 2 Six samples of the sintered ceramic obtained in Example 2 were used as a membrane for an electrode and installed in an electrochemical cell containing a buffer solution. A measurement of the variation of the potential difference (ddp) between this electrode and a commercial reference electrode (Redrod, marketed by the company Radiometer) for different buffer solutions was carried out at 25 ° C for three samples and at 60 ° C for the other three samples. The results are shown in FIG. 5.
  • the potential difference E / Eref (in mV) is given on the ordinate and the pH is given on the abscissa.
  • the curves materialized respectively by the signs ⁇ , and O correspond to the measurements carried out at 60 ° C.
  • a pH measuring device has been produced in which the reference electrode and the pH indicator electrode comprise a ceramic with a perovskite structure as an active element.
  • Each of the two electrodes is constituted by a glass tube closed at its lower part by a ceramic membrane, said tube contains a buffer solution, in which an internal electrode of the Pt / Hg / Hg 2 Cl 2 type is immersed.
  • the ceramic membrane consists of a sintered ceramic obtained by a method according to Example 2.
  • the percentage of particles indicated in a column corresponds to the percentage of grains having a size less than the value indicated in the second row of the same column.
  • the powder was subjected to grinding in a Fritsch P7 planetary mill using zirconia balls in ethanol, for a period of 105 min.
  • the powder obtained after grinding has a specific surface of 143,682 cm 2 / cm 3 .
  • the particle size distribution is given in Table 4. Table 4
  • ground powder was subjected to compaction under a pressure of 488 Mpa, - the compacted pellet formed was heated to raise its temperature by 5 ° C per min, to 1150 ° C and this temperature was maintained for 10 hours.
  • FIG. 6 represents a photograph (magnification ⁇ 3000) with a Hitachi 2300 electron microscope of the sintered pellet thus obtained.
  • the grains have an octahedral geometry with well-drawn edges and homogeneous dimensions (approximately 1 ⁇ m for small grains and approximately 3 ⁇ m for large grains. There is no vacuum between the grains.
  • We tested the measuring device by immersing the two electrodes, connected to a millivoltmeter with high input impedance, successively in solutions at pH 4, pH 7, pH 10 and pH 4. The variation of the ddp and the temperature over time depending on the placement of the electrodes in the different solutions is represented in FIG. 7.
  • the upper curve represents the variation of the ddp (expressed in mV) as a function of time according to the pH.
  • the lower curve represents the variation of the temperature T (expressed in ° C) as a function of time t (expressed in seconds), that is to say as a function of the variation in pH.

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EP03758261A 2002-08-29 2003-08-22 Keramik mit perovskit-struktur, dessen verwendung als referenzelektrode Withdrawn EP1532084A1 (de)

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FR0210734A FR2843960B1 (fr) 2002-08-29 2002-08-29 Ceramique a structure perovskite, son utilisation comme electrode de reference
FR0210734 2002-08-29
PCT/FR2003/002563 WO2004020361A1 (fr) 2002-08-29 2003-08-22 Ceramique a structure perovskite, son utilisation comme electrode de reference.

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NL1028264C2 (nl) * 2005-02-14 2006-08-15 Hydrion Membraanmodule voor toepassing in een referentie-elektrode, een referentie-elektrode en werkwijze voor het vervaardigen van een membraanmodule.

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WO1989010813A1 (en) * 1988-05-13 1989-11-16 Research Corporation Technologies, Inc. Ceramic electrode material and electrical devices formed therewith
JP3838284B2 (ja) * 1996-10-11 2006-10-25 株式会社ジーエス・ユアサコーポレーション 非水電解質二次電池

Non-Patent Citations (4)

* Cited by examiner, † Cited by third party
Title
CHANG WAN BAN, GYEONG MAN CHOI: "The effect of sintering on the grain boundary conductivity of lithium lanthanum titanates", SOLID STATE IONICS, vol. 140, no. 3-4, 1 April 2001 (2001-04-01), pages 285 - 292, XP004240074, DOI: doi:10.1016/S0167-2738(01)00821-9 *
J.-G. KIM, H.-G. KIM, H.-T. CHUNG: "Microstructure-ionic conductivity relationships in perovskite lithium lanthanum titanate", JOURNAL OF MATERIALS SCIENCE LETTERS, vol. 18, no. 6, 1 March 1999 (1999-03-01), XP000853023, ISSN: 0261-8028, DOI: doi:10.1023/A:1006606817633 *
O. BOHNKE, CL. BOHNKE, J.L. FOURQUET: "Mechanism of ionic conduction and electrochemical intercalation of lithium into the perovskite lanthanum lithium titanate", SOLID STATE IONICS, vol. 91, no. 1-2, 21 June 1996 (1996-06-21), pages 21 - 31, XP004071602, ISSN: 0167-2738, DOI: doi:10.1016/S0167-2738(96)00434-1 *
SAMUEL J. SCHNEIDER, JR. (VOLUME CHAIRMAN): "Ceramics and glasses", vol. 4, 1 January 1992, ASM INTERNATIONAL, US, ISBN: 0-87170-282-7 *

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AU2003274274A8 (en) 2004-03-19

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