EP1532083A1 - Keramik mit perovskit-struktur und deren verwendung als ph-elektrode - Google Patents

Keramik mit perovskit-struktur und deren verwendung als ph-elektrode

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Publication number
EP1532083A1
EP1532083A1 EP03758260A EP03758260A EP1532083A1 EP 1532083 A1 EP1532083 A1 EP 1532083A1 EP 03758260 A EP03758260 A EP 03758260A EP 03758260 A EP03758260 A EP 03758260A EP 1532083 A1 EP1532083 A1 EP 1532083A1
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Withdrawn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
EP03758260A
Other languages
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
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 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 EP1532083A1 publication Critical patent/EP1532083A1/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Withdrawn legal-status Critical Current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
    • 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
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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
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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
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    • 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
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    • G01N27/30—Electrodes, e.g. test electrodes; Half-cells
    • G01N27/302—Electrodes, e.g. test electrodes; Half-cells pH sensitive, e.g. quinhydron, antimony or hydrogen electrodes
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    • G01N27/26—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrochemical variables; by using electrolysis or electrophoresis
    • G01N27/416—Systems
    • G01N27/4166—Systems measuring a particular property of an electrolyte
    • G01N27/4167—Systems measuring a particular property of an electrolyte pH
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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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    • C04B2235/3231—Refractory metal oxides, their mixed metal oxides, or oxide-forming salts thereof
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Definitions

  • the present invention relates to a ceramic with a perovskite structure, as well as its use as a pH measurement electrode.
  • a frequently used measuring electrode is an electrode of said glass electrode, constituted by the electrochemical chain Ag / AgCl / internal solution at pH 7 / glass.
  • 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
  • the object of the present invention is to provide a ceramic with a perovskite structure having a particular structure which makes it sensitive to variations in pH of a medium, a method for preparing it, and a measuring electrode comprising said ceramic as active element.
  • 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 ) - 2x E0 3 , in which:
  • 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 d state '+5 or +6 oxidation;
  • 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 one 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 ) - ⁇ Li 3x ( ⁇ / 3) - 2x 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 of less than 5 ⁇ m; the powder is compacted under a pressure of 251 to 740 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 l-30 ° C / min.
  • the sintering time is advantageously between 5 and 12 hours. A duration of 10 hours is generally suitable.
  • the initial ceramic powder used is obtained by grinding a ceramic having the desired composition, in a planetary mill of the ball mill type or of the disc mill type.
  • a ceramic having the desired composition in a planetary mill of the ball mill type or of the disc mill type.
  • the P7 type zirconia ball mill marketed by the company Fritsch.
  • Fritsch By grinding for a period of 45 min carried out on a starting powder having a specific surface of the order of 3700 cm 2 / g and of which 50% of the grains have a dimension of less than 18.25 ⁇ m, we obtains a powder of which 75% of the grains have a dimension of less than 5.5 ⁇ m, the specific surface (21,361 cm 2 / g) being multiplied by about 5.5 compared to the initial powder.
  • the ceramic powder is obtained by a sol-gel process.
  • a compound La ( / 3 ) _ x Li 3x (_ / 3 ) -_ x Ti0 3 can be prepared from a solution A obtained by dissolving nitrate or acetate in a minimum of anhydrous ethanol lithium and nitrate or lanthanum acetate in stoichiometric proportions, and a solution B obtained by dissolving the titanium isopropoxide in anhydrous methanol.
  • the mixture of solutions A and B in stoichiometric proportions causes a hydrolysis which gives a gel. Heating the gel to a temperature of 150 ° C gives a dry product. Said dry product is then heated to a temperature of the order of 400 ° C to remove the organic part.
  • the ceramic is then obtained by heating at 1000 ° C for about 12 hours.
  • the other ceramics of the invention can be obtained in a similar manner.
  • a measuring 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 metal and ceramic can be achieved using an adhesive. It can also be obtained by vacuum deposition of the metal on the ceramic, this process being particularly suitable when the ceramic is obtained in the form of a thin film by a sol-gel process.
  • a pH measurement device comprises a reference electrode insensitive to variations in pH, and a measurement electrode having a high sensitivity to variations in pH in a medium, the two electrodes being connected by a millivoltmeter with high input impedance.
  • the electrode according to the present invention is particularly well suited for be used as a measuring electrode in such a device.
  • FIG. 1 represents the diagram of a pH measuring device in which the measuring electrode has the "membrane" configuration.
  • This device is constructed according to the electrochemical chain "reference electrode / buffer solution / M / MX / X " / ceramic ". It comprises a measurement electrode according to the invention (1), a reference electrode (2), a millivoltmeter (3) (for example of the MINISIS 8000 type marketed by the company Tacussel, or of the pHm210 type marketed by the company Radiometer), a device (4) for signal processing (for example an Agilent acquisition center). electrodes are immersed in the same thermostated solution, not shown, for which it is desired to determine the pH or the concentration of alkaline ions.
  • the reference electrode (2) can be of the REDROD type sold by the company Radiometer.
  • (1) comprises a glass tube (5) closed at its lower part by a ceramic membrane (6) according to the invention
  • the tube contains a buffer solution (7) consisting of an aqueous solution saturated with KC1 and having a pH kept constant during the measurement (for example a saturated solution of KC1 at pH 1).
  • An internal electrode (8) is immersed in the buffer solution (7).
  • the internal electrode (8) can be of the Pt / Hg / Hg 2 Cl 2 type .
  • the reference electrode (2) is connected directly to the millivoltmeter (3).
  • the indicator electrode is connected to the millivoltmeter via the internal electrode (8).
  • FIG. 2 represents the diagram of a device for measuring pH in which the measurement electrode is of the "all solid" type.
  • This device is constructed according to the electrochemical chain "reference electrode / metal / ceramic".
  • the measuring device comprises a measuring electrode according to the invention (1 '), a reference electrode (2') (for example a said Redrod electrode) and a millivoltmeter with high input impedance (3 ').
  • the measuring electrode is constituted by a tube closed at its lower part by a ceramic disc (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 ').
  • a measurement electrode according to the invention is associated, in a measurement device, with a reference electrode, the sensitive element of which is a ceramic with a perovskite structure, which may have the same chemical composition as the element. active of the present reference electrode, but a different structure and specific surface.
  • a reference electrode can be constructed in the form of a membrane electrode or in the "all solid" form, in the same way as the measurement electrode according to the invention.
  • the ceramic membrane forming the reference electrode has a perovskite structure and exhibits the following properties: its composition corresponds to the formula L ⁇ 2/3) - ⁇ A '3 ⁇ ( ⁇ / 3) 3 -2 ⁇ E'0 , in which :
  • L ' represents at least one element chosen from Sb, Bi, lanthanides and non-toxic and non-radioactive alkaline earth 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;
  • * 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.
  • 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 dimension greater than 18 ⁇ m, compacting the powder under a pressure of 251 to 500 Mpa, then sintering said compacted powder at a temperature between 1050 and 1350 ° C.
  • the use of a measurement electrode, and possibly of a reference electrode comprising a ceramic membrane according to the invention 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.
  • the pH measuring devices in which the measuring electrode according to the invention is in the "all solid" configuration is particularly advantageous in environments requiring high temperatures and / or pressures, which is common in the 'food industry.
  • Particular preference will be given to devices in which the reference 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 distribution of particle size is given in the tables in which the percentage of particles shown in a column is the percentage of grains having a dimension less than the value in the 2nd row of the same column.
  • the powder was subjected to grinding in a Fritsch P7 planetary mill using zirconia beads in ethanol, for a period of 105 min.
  • the specific surface of said powder is 28,392 cm 2 / g.
  • the particle size distribution is given in Table 2. It is noted that 75% of the grains have a dimension of less than 3 ⁇ m. Table 2
  • Said 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. 3 represents a photograph (magnification ⁇ 3000) with a Hitachi 2300 electron microscope of the sintered pellet.
  • the grains have an octahedral geometry with well-drawn edges and homogeneous dimensions
  • Sintered pellets obtained by the method of Example 1 were used as membranes of the measurement electrode of a pH measurement device as shown in FIG. 1.
  • Thermostated solutions, the pH of which was determined at 1 using the measuring electrode according to the invention are solutions at different pHs sold by the company Carlo Erba.
  • Measurements of variation of the potential difference (ddp) as a function of the variation of the pH were made on the one hand at 25 ° C, and on the other hand at 60 ° C, using a Redrod electrode from the company Radiometer as a reference electrode.
  • FIG. 4 represents the variation of the ddp at 25 ° C. as a function of the variation of the pH of the medium, for 4 samples obtained according to the method described in example 1.
  • FIG. 5 represents the variation of the ddp at 60 ° C. as a function of the variation of the pH of the medium, for 2 samples obtained according to the method of example 1.
  • FIG. 6 represents the variations of the ddp as a function of time, when the electrodes are passed successively through various buffer solutions having different pHs, for an electrode comprising a ceramic membrane manufactured according to example 1, and for an electrode Radiometer XC100 glass from the company Radiometer.
  • the curve in solid lines corresponds to the electrode of the invention.
  • the dotted curve corresponds to the glass electrode.
  • the time t is given in seconds on the abscissa axis
  • the ddp with respect to a reference electrode E / Eref is given in mV on the ordinate axis. It appears that performances similar to those of the glass electrode can be obtained with the electrode of the invention which does not have the abovementioned drawbacks of the glass electrode.
  • a sintered ceramic pellet was prepared by a process identical to that described in Example 1, only modifying the duration of the grinding of the initial powder before sintering. For a grinding time of 45 min, a powder was obtained whose specific surface is 21,361 cm 2 / g. The particle size distribution of said powder is given in Table 3. It is noted that 50% of the particles have a size less than about 3 ⁇ m.
  • Example 2 The sintered pellet obtained according to a process similar to that of Example 1 was used to make a measuring electrode which was tested in a device similar to that of Example 2. Similar results were obtained.
  • 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 is a sintered ceramic obtained by the method of Example 1.
  • 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. 7 represents a photograph (magnification ⁇ 3000) with a Hitachi 2300 electron microscope of the sintered pellet. 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.
  • the measuring device was tested by immersing the two electrodes, connected to a high input impedance millivoltmeter, successively in solutions at pH 4, pH 7, pH 10 and again at pH 4.
  • the variation of the ddp and of the temperature over time as a function of the placement of the electrodes in the different solutions is represented in FIG. 8.
  • the upper curve represents the variation of the ddp (expressed in mV) as a function of time according to the pH.
  • the bottom curve represents the variation of temperature T (expressed in ° C) as a function of time t

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EP03758260A 2002-08-29 2003-08-22 Keramik mit perovskit-struktur und deren verwendung als ph-elektrode Withdrawn EP1532083A1 (de)

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FR0210730A FR2843959B1 (fr) 2002-08-29 2002-08-29 Ceramique a structure perovskite, son utilisation comme electrode de mesure de ph
FR0210730 2002-08-29
PCT/FR2003/002562 WO2004020360A1 (fr) 2002-08-29 2003-08-22 Ceramique a structure perovskite, son utilisation comme electrode de mesure ph.

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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)

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Title
CHANG WAN BAN, GYEONG MAN CHOI: "The effect of sintering on the grain boundary conductivbity of lithium lanthanum titanates", SOLID STATE IONICS, vol. 140, no. 3-4, 17 December 2000 (2000-12-17), 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 MATERIAL SCIENCE LETTERS, vol. 18, no. 6, 31 December 1999 (1999-12-31), pages 493 - 496, XP000853023, ISSN: 0261-8028, DOI: doi:10.1023/A:1006606817633 *
O. BOHNKE, C. BOHNKE, J.L. FOURQUET: "Mechanism of ionic conductivity 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, 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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FR2843959B1 (fr) 2006-01-20
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WO2004020360A1 (fr) 2004-03-11
AU2003274273A8 (en) 2004-03-19

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