Scandied zirconia fused product

Abstract

Polycrystalline molten product of formula (Sc2O3)yAx(ZrO2 + HfO2)1-xy, with 0.030 ≤ y ≤ 0.150, and 0.000 ≤ x ≤ 0.070, and x ≤ yA denoting an additive selected from Y2O3, Al2O3, CeO2, Yb2O3, Gd2O3, MnO, Bi2O3, La2O3, Pr2O3, Nd2O5, Sm2O3, Eu2O3, Tb4O7 and mixtures thereof, ZrO2 + HfO2 + Sc2O3 + A representing more than 98% of the mass of said molten product, MnO expressing the total content of manganese oxides expressed as MnO, Pr2O3 expressing the total content of oxides of Praseodymium expressed as Pr2O3,Nd2O5, representing the total content of neodymium oxides expressed as Nd2O5,Tb4O7, representing the total content of terbium oxides expressed as Tb4O7. No abbreviated figure.

Description

Title of the invention: Scandied zirconia molten product technical field

[0001] The present invention relates to a molten product of scandiated zirconia and a method for manufacturing such a product. The invention also relates to a device comprising a molten product according to the invention or a molten product manufactured or capable of being manufactured by a method according to the invention. State of the art

[0002] Scandied zirconia products are used in particular as an electrolyte and as an electrode material, especially anodes, in solid oxide electrochemical devices, in particular a solid oxide electrolysis cell (or "Solid Oxide Electrolysis Cell" or "SOEC" in English) or a solid oxide fuel cell (or "Solid Oxide Fuel Cell" or "SOFC" in English).

[0003] Scandied zirconia powders are generally produced by solid-phase sintering, coprecipitation, or sol-gel processes. However, these processes are complex and expensive to implement.

[0004] There is therefore a permanent need to reduce the complexity and manufacturing cost of a scandiated zirconia product suitable for use in the aforementioned applications.

[0005] One object of the invention is to satisfy, at least partially, this need. Summary of the invention

[0006] According to a first principal aspect of the invention, this goal is achieved by means of a polycrystalline molten product of formula (Sc2O3)yAx(ZrO2 + HfO2)ixy, with 0.030 < y < 0.150, and 0.000 < x < 0.070, and x < y A designating an additive chosen from Y2O3, Al2O3, CeO2, Yb2O3, Gd2O3, MnO, Bi2O3, La2O3, Pr2O3, Nd2O5, Sm2O3, Eu2O3, Tb4O7 and their mixtures, ZrO2 + HfO2 + Sc2O3 + A representing more than 98% of the mass of said molten product, MnO expressing the total content of manganese oxides expressed in the form of MnO, Pr2O3 expressing the total content of praseodymium oxides expressed in the form Pr2 O3, Nd2O5 expressing the total content of neodymium oxides expressed as Nd2O 5, Tb4O7 expressing the total content of terbium oxides expressed in the form Tb4O7.

[0007] Such a product has proven well suited to constitute an electrode, in particular an anode, and an electrolyte of a solid oxide electrochemical device, in particular a solid oxide electrolysis cell or a solid oxide fuel cell.

[0008] Unexpectedly, the inventors discovered that it was not necessary to implement a complex process to manufacture a product, in particular a powder, suitable for the manufacture of an electrode, in particular an anode, or an electrolyte, as according to the prior art. A simple melting process is sufficient.

[0009] Preferably, a molten product according to the invention further comprises one and preferably several of the following optional characteristics: - the additive is chosen from A12O3, CeO2, Yb2O3 and their mixtures, preferably from A12O3, CeO2 and their mixtures, preferably is CeO2; - the product comprises, in mass percentages based on the crystallized phases of zirconia and hafnia, an amount of (monoclinic zirconia + monoclinic hafnia) less than or equal to 30%, preferably less than or equal to 10%; - the product is in the form of a particle with a sphericity greater than 0.8; - 0.130 > y > 0.040 and / or x < 0.050; - 0.110 > y > 0.050 and / or x < 0.030; - x < 0.015; - y = 0.060 or y = 0.100; - x = 0.000 or x > 0.005; - x = 0.01 and the additive is CeO2 or is A12O3; - the product has an average zirconia crystallite size greater than or equal to 5 nm and less than or equal to 10 nm.

[0010] The invention also relates to a powder comprising more than 90%, preferably more than 95%, preferably 100% by mass of particles in a molten product according to the invention.

[0011] The powder preferably has a median size D50 greater than 0.2 pm and less than 50 pm, preferably less than 1 pm.

[0012] The invention also relates to a method for manufacturing a product according to the invention, said method comprising the following steps: a) mixing of raw materials so as to form a starting charge; b) melting of the starting charge until a molten material is obtained; c) cooling until complete solidification of said molten material, said starting charge being adapted, in step a), to obtain, at the end of step c) a molten product according to the invention; d) optionally, grinding said melted product, preferably until a powder is obtained; e) optionally, particle size selection of said melted product; f) before or after step d), optionally, annealing heat treatment of said melted product.

[0013] In step a), the starting charge preferably contains a scandiated zirconia.

[0014] The invention also relates to a molten product obtained or capable of having been obtained by a process according to the invention.

[0015] The invention further relates to an electrode, in particular an anode, and an electrolyte comprising, or even being constituted by, a molten product according to the invention or obtained or capable of having been manufactured by a process according to the invention, in particular obtained by sintering a particulate mixture comprising a powder according to the invention.

[0016] The invention finally relates to a solid oxide electrochemical device, in particular a solid oxide electrolysis cell or a solid oxide fuel cell, comprising a said electrode according to the invention, in particular an anode, and / or a said electrolyte according to the invention.

[0017] Furthermore, the inventor has observed that the molten product according to the invention has a surprisingly small average size of zirconia crystallites.

[0018] According to a second principal aspect, the invention also relates to a product of formula (Sc2O3)yAx(ZrO2 + HfO2)ixy, with 0.030 < y < 0.150, and 0.000 < x < 0.070, and x < y A designating an additive chosen from Y2O3, Al2O3, CeO2, Yb2O3, Gd2O3, MnO, Bi2O3, La2O3, Pr2O3, Nd2O5, Sm2O3, Eu2O3, Tb4O7 and their mixtures, ZrO2 + HfO2 + Sc2O3 + A representing more than 98% of the mass of said product, MnO expressing the total content of manganese oxides expressed in the form of MnO, Pr2O3 expressing the total content of praseodymium oxides expressed in the form Pr2 O3, Nd2O5 expressing the total content of neodymium oxides expressed as Nd2O

[0019] Tb4O7 expressing the total content of terbium oxides expressed in the form Tb4O 7, said product having an average zirconia crystallite size greater than or equal to 5 nm and less than or equal to 10 nm.

[0020] Except for technical incompatibility, all optional features of a product cast according to the first main aspect of the invention are optionally applicable to the product according to the second main aspect of the invention. Definitions

[0021] A "molten product" is a product directly obtained by solidification of a molten material resulting from the melting of a starting charge. "Directly obtained" means that the molten product is obtained immediately after said solidification.

[0022] A "molten material" is a mass made liquid by heating a starting charge, which may contain some solid particles, but in insufficient quantity for them to structure said mass. To maintain its shape, a molten material must be contained in a vessel.

[0023] A "polycrystalline" material is a solid material composed of a multitude of crystallites of varying sizes and orientations, as opposed to a single-crystal material consisting of a single crystal. The polycrystalline nature of a material can, for example, be demonstrated by X-ray diffraction and / or by scanning electron microscopy. Such observations reveal grain boundaries. Without special precautions, a molten product is polycrystalline.

[0024] By "particle" we mean a solid object whose dimensions are all less than 10 mm.

[0025] The sphericity of a particle is the ratio between its smallest dimension and its largest dimension.

[0026] By "block" we mean a solid object that is not a particle.

[0027] A “powder” is a collection of particles.

[0028] The percentiles or "percentiles" 10 (Di0), 50 (D50), 90 (D90), and 99.5 (D995) are the particle sizes corresponding to the percentages, by mass, of 10%, 50%, 90%, and 99.5%, respectively, on the cumulative particle size distribution curve of the powder, with the particle sizes listed in ascending order. For example, 10%, by mass, of the powder particles have a size less than Di0, and 90%, by mass, of the particles have a size greater than or equal to Di0. The percentiles can be determined using a distribution particle size analysis carried out using a laser particle size analyzer, for example, a Partica LA-950V2 marketed by the company HORIBA.

[0029] The "minimum size of a powder" is defined as the 10th percentile (Di0) of said powder.

[0030] The "median size of a powder" is defined as the 50th percentile (D50) of said powder.

[0031] The "maximum size of a powder" is defined as the 99.5th percentile (D99>5) of said powder.

[0032] By “precursor” of a compound or element, we mean a constituent capable of providing said compound or element, respectively, during the implementation of a manufacturing process according to the invention.

[0033] A total content of several oxides, for example ZrO2 + HfO2, does not imply that each of said oxides is present, even if, in one embodiment, each of said oxides is present.

[0034] When reference is made to zirconia or ZrO2, this should be understood to mean (ZrO2 + HfO2), with HfO2 < 5%, preferably HfO2 < 3%. Indeed, a small amount of HfO2, which is chemically inseparable from ZrO2 and has similar properties, is always naturally present in zirconia sources. Hafnium oxide is therefore not considered an impurity.

[0035] Similarly, when reference is made to the element zirconium, it is necessary to understand the element Zr and the traces of the element Hf present in the source of the element Zr.

[0036] By "impurities" is meant constituents introduced unintentionally. Impurities are not necessary constituents, but only tolerated.

[0037] Unless otherwise indicated, the percentages used to define a composition are mass percentages based on the mass of the product.

[0038] The verbs "comprendre", "comporter" and "présenter" must be interpreted in a non-restrictive manner, unless otherwise indicated. Detailed description

[0039] Other features and advantages of the present invention will become apparent from the following detailed description, which is provided for illustrative and non-limiting purposes. Melted product

[0040] A molten product according to the invention preferably has one or more of the following optional characteristics: - The additive is chosen from A12O3, CeO2, Yb2O3 and mixtures thereof, preferably from A12O3, CeO2 and mixtures thereof. Preferably the additive is CeO2. - in one embodiment, the content of "other constituents", that is to say constituents other than ZrO2, HfO2, Sc2O3, Y2O3, Al2O3, CeO2, Yb2O3, Gd2O3, manganese oxides, Bi2O3, La2O3, praseodymium oxides, Nd2O5, Sm2O3, Eu2 03 and terbium oxides is less than 1.5%, preferably less than 1%, preferably less than 0.5%, preferably less than 0.3%; - y > 0.040, preferably y > 0.050, and / or y < 0.130, preferably y < 0.110; - in one embodiment, x = 0.000; - in one embodiment, x < 0.050, preferably x < 0.040, preferably x < 0.030, preferably x < 0.020, preferably x < 0.015 and x > 0.005, preferably x > 0.007; - in one embodiment, y > 0.040, preferably y > 0.050, and y < 0.130, preferably y < 0.110, and x < 0.050, preferably x < 0.040, preferably x < 0.030, preferably x < 0.020, preferably x < 0.015 and x > 0.005, preferably x > 0.007; - in one embodiment, y > 0.040, preferably y > 0.050, and y < 0.130, preferably y < 0.110, and x < 0.050, preferably x < 0.040, preferably x < 0.030, preferably x < 0.020, preferably x < 0.015 and x > 0.005, preferably x > 0.007, and the additive is chosen from A12O3, CeO2, Yb2O3 and their mixtures, preferably from A12O3, CeO2 and their mixtures; - In one embodiment, y = 0.060 or y = 0.100; - In one embodiment, y = 0.060 and x = 0.000; - In one embodiment, y = 0.060 and x > 0.005; - In one embodiment, y = 0.060, x = 0.010 and the additive is CeO2; - In one embodiment, y = 0.060, x = 0.010 and the additive is A12O3; - In one embodiment, y = 0.100 and x = 0.000; - In one embodiment, y = 0.100 and x > 0.005; - In one embodiment, y = 0.100, x = 0.010 and the additive is CeO2; - In one embodiment, y = 0.100, x = 0.010 and the additive is A12O3; - the molten product comprises, in mass percentages based on the crystallized phases of zirconia and hafnia, an amount of (monoclinic zirconia + monoclinic hafnia) less than or equal to 30%, preferably less than or equal to 25%, preferably less than or equal to 20%, preferably less than or equal to 15%, preferably less than or equal to 10%; - the average size of zirconia crystallites is preferably greater than or equal to 5 nm, preferably greater than or equal to 6 nm, preferably greater than or equal to 7 nm, and preferably less than or equal to 100 nm, preferably less than or equal to 80 nm, preferably less than or equal to 60 nm, preferably less than or equal to 50 nm, preferably less than or equal to 30 nm; - in one embodiment, particularly when the molten product has not undergone annealing heat treatment step f), the average size of the crystallites of zirconia is greater than or equal to 5 nm, preferably greater than or equal to 6 nm, preferably greater than or equal to 7 nm, and less than or equal to 10 nm.

[0041] In one embodiment, the molten product is in the form of an object, preferably a particle, having a sphericity greater than 0.5, preferably greater than 0.6, preferably greater than 0.7, or even greater than 0.8.

[0042] The invention also relates to a powder comprising more than 90% by mass, or even more than 95%, or even substantially 100% of particles in a molten product according to the invention. The powder preferably has a median size D50 greater than 0.2 pm, preferably greater than 0.3 pm and / or, preferably, less than 50 pm, preferably less than 30 pm, preferably less than 10 pm, preferably less than 5 pm, preferably less than 3 pm, preferably less than 1 pm, preferably less than 0.7 pm.

[0043] Preferably, the minimum size of the powder according to the invention is greater than 0.05 pm, preferably greater than 0.07 pm.

[0044] Preferably, the maximum size of the powder according to the invention is less than 2 pm, preferably less than 1.5 pm.

[0045] Preferably, the D90 percentile of the powder according to the invention is less than 1.5 pm, preferably less than 1.0 pm.

[0046] In one embodiment, a powder according to the invention is sintered, optionally with at least one other powder, said at least one other powder preferably being a powder of a metal oxide, to form an electrode, preferably an anode or an electrolyte of a solid oxide electrochemical device, in particular a solid oxide electrolysis cell or a solid oxide fuel cell. Process

[0047] The invention also relates to a method for manufacturing a molten product comprising steps a) to c) and optionally d) to f).

[0048] In one embodiment, the process according to the invention comprises a step d) and a step e).

[0049] In one embodiment, the process according to the invention comprises a step d), a step e) and a step f).

[0050] Step f) can in particular be implemented to decrease the amount of crystallized phase of (monoclinic zirconia + monoclinic hafnia) in the molten product according to the invention.

[0051] In step a), a starting charge for manufacturing a molten product according to the invention is formed from compounds of zirconium, hafnium, scandium, and optionally from compounds of cerium, aluminum, yttrium, ytterbium, gadolinium, manganese, bismuth, europium, lanthanum, praseodymium, neodymium, samarium and terbium, in particular in the form of oxides and / or carbonates and / or hydroxides and / or oxalates and / or nitrates.

[0052] Preferably, at least one, or even all, of the elements zirconium, hafnium, scandium, and optionally the elements cerium, aluminium, yttrium, ytterbium, gadolinium, manganese, bismuth, europium, lanthanum, praseodymium, neodymium, samarium and terbium, are introduced into the starting charge in the form of oxides.

[0053] Preferably, zirconium, hafnium, scandium compounds, and optionally cerium, aluminium, yttrium, ytterbium, gadolinium, manganese, bismuth, europium, lanthanum, praseodymium, neodymium, samarium and terbium compounds, are selected from ZrO2, Sc2O3, carbonates and / or hydroxides and / or oxides of the elements cerium, aluminium, yttrium, ytterbium, gadolinium, manganese, bismuth, europium, lanthanum, praseodymium, neodymium, samarium and terbium, respectively.

[0054] In one embodiment, at least one of said compounds is chosen to provide at least two elements selected from zirconium, hafnium, scandium, cerium, aluminum, yttrium, ytterbium, gadolinium, manganese, bismuth, europium, lanthanum, praseodymium, neodymium, samarium, and terbium. For example, such a compound may be ceria-treated zirconia.

[0055] In one embodiment, the starting charge contains scandi zirconia, preferably in powder form. In said embodiment, the scandi zirconia present in the starting charge may also contain at least one oxide selected from the oxides of aluminium, yttrium, ytterbium, gadolinium, manganese, bismuth, europium, lanthanum, praseodymium, neodymium, samarium and terbium, in particular when the molten product obtained at the end of step c) contains said at least one oxide selected from the oxides of aluminium, yttrium, ytterbium, gadolinium, manganese, bismuth, europium, lanthanum, praseodymium, neodymium, samarium and terbium. This method of embodiment advantageously allows the use of scraps or offcuts of scandiated zirconia.

[0056] Preferably, the compounds providing zirconium, hafnium, scandium, and optionally cerium, aluminum, yttrium, ytterbium, gadolinium, manganese, bismuth, europium, lanthanum, praseodymium, neodymium, samarium, and terbium together represent more than 90%, preferably more than 99%, by mass percentage, of the constituents of the starting feed. Preferably, these compounds, together with the impurities, represent 100% of the constituents of the starting feed.

[0057] Preferably, no compound other than those providing zirconium, hafnium, scandium and optionally cerium, aluminium, yttrium, ytterbium, gadolinium, manganese, bismuth, europium, lanthanum, praseodymium, neodymium, samarium and terbium is voluntarily introduced into the starting charge.

[0058] Selecting the raw materials for the starting charge so that the molten product obtained at the end of step c) has a composition conforming to the desired one presents no difficulty for a person skilled in the art. They know how to adapt the composition of the starting charge, particularly according to the loss of certain raw materials during melting and the melting conditions used. This loss is small, and the quantities of zirconium, hafnium, scandium, and optionally cerium, aluminum, yttrium, ytterbium, gadolinium, manganese, bismuth, europium, lanthanum, praseodymium, neodymium, samarium, and terbium from the starting charge are found almost entirely in the polycrystalline molten product produced.

[0059] The starting charge is preferably in the form of a particulate mixture. The particle sizes of the powders used can be those commonly encountered in melting processes.

[0060] An intimate mixing of the raw materials can be carried out in a mixer. This mixture is then poured into a melting furnace.

[0061] At step b), the starting charge is melted.

[0062] All known furnaces are suitable, such as an induction furnace, a plasma furnace, or a Héroult-type electric arc furnace, provided they allow for the melting of the starting material. Crucible melting in a heat treatment furnace, preferably an electric furnace, is also feasible. Electrofusion advantageously allows the production of large quantities of molten product with attractive yields. Preferably, the starting material is melted in a Héroult-type arc furnace. For example, a Héroult-type arc furnace with two electrodes, a chamber with a diameter of approximately 0.8 m, and a capacity of approximately 180 kg of molten material can be used.

[0063] Preferably when a Héroult furnace is used, the electrodes do not immerse themselves in the bath of molten material.

[0064] In step b), the energy supplied is preferably greater than 1150 kWh / T of starting load, preferably greater than 1300 kWh / T. Preferably, the energy supplied is between 1150 kWh / T and 2800 kWh / T. The electrical voltage is, for example, 160 Volts.

[0065] After melting, the starting charge is in the form of a molten material, which may contain some solid particles, but in an insufficient quantity. so that they can structure the molten material. By definition, to retain its shape, a molten material must be contained in a container.

[0066] It is possible to improve the quality of the mixing of the molten material by bubbling a gas, as mentioned in FR 1 208 577. Said bubbling gas can be air or oxygen.

[0067] The general environment of the molten material is preferably oxidizing, preferably air.

[0068] Preferably, step b) is carried out at atmospheric pressure.

[0069] In step c), the cooling rate is preferably less than 1000°C / s, preferably less than 100°C / s, preferably less than 50°C / s.

[0070] In a first embodiment of step c), step c) comprises the following steps: c1) dispersion of the molten material in the form of liquid droplets, c2) solidification of these liquid droplets by contact with a fluid, preferably a gas, so as to obtain particles of molten product.

[0071] The molten product according to the invention, in particular manufactured according to this first embodiment, can be presented, at the end of step c), in the form of a powder of particles whose minimum size is greater than 0.005 mm and whose maximum size is less than 5 mm.

[0072] At step cl), a stream of the molten liquid is dispersed into liquid droplets.

[0073] Dispersion can result from blowing molten material through the mesh.

[0074] The molten particles may be spherical or not, hollow or solid, depending in particular on the blowing conditions and / or the composition of the molten material.

[0075] Any other method of atomizing a molten material, known to those skilled in the art, is conceivable.

[0076] At step cl), the mesh of said molten material is brought into contact with a "dispersion" fluid, preferably a "dispersion" gas.

[0077] Preferably, the dispersion fluid is a gas having an oxygen volume content greater than 20%, preferably air and / or water vapor, preferably air.

[0078] In step c2), the liquid droplets are transformed into solid particles by contact with a "solidification" fluid, preferably a solidification gas, which can be chosen from those described for step c1). Preferably, the process is adapted so that, as soon as it is formed, the molten liquid droplet is in contact with the solidification fluid, which may be the same as or different from the dispersion fluid used for step c1) and which, preferably, is the same as the dispersion fluid used for step c1).

[0079] In one embodiment, step c2) involves cooling the droplets by immersion in water.

[0080] Preferably, steps cl) and c2) include cooling the droplets by blowing a gas having an oxygen volume content greater than 20%, preferably air, at ambient temperature.

[0081] Preferably, no other means of solidification than cooling by contact with the solidification fluid is used.

[0082] Preferably, the dispersion (step c1)) and solidification (step c2)) are substantially simultaneous, the molten material being dispersed by a fluid, preferably a gas, capable of cooling and solidifying this material. Preferably, contact with the fluid is maintained at least until the droplets have completely solidified.

[0083] At the end of step c2), we obtain a set of solid particles which has a minimum size greater than or equal to 0.01 pm and a maximum size less than or equal to 5 mm, or even less than or equal to 3 mm, depending on the dispersion conditions.

[0084] In a second embodiment, step c) comprises the following steps: cl') pouring the molten material into a mold; c2') solidification by cooling of the molten material poured into the mold until a block is obtained that is at least partially solidified; c3') demolding of the block.

[0085] In step cl'), the molten material is poured into a mold capable of withstanding the molten bath. Preferably, molds made of graphite, cast iron, or such as those defined in US 3,993,119 are used. In the case of an induction furnace, the coil is considered to constitute a mold.

[0086] Preferably, the casting is carried out under a "casting" gas having a volumetric oxygen content greater than 20%, preferably under air.

[0087] At step c2'), the molten material poured into the mold is cooled until a block is obtained that is at least partially solidified.

[0088] At step c3'), the block is demolded. Preferably, the block is demolded as soon as it has sufficient rigidity to retain substantially its shape.

[0089] Preferably, in step c2') and / or after step c3'), the molten material being solidified is brought into contact, directly or indirectly, with a "solidification" fluid, preferably a "solidification" gas, which may be identical or different from that described for step c1'). This contacting may be carried out as soon as the pouring is complete.

[0090] To facilitate contact between the molten material and the solidification fluid, preferably the solidification gas, it is preferable to demold the block as quickly as possible, if possible before complete solidification, and to then immediately begin contacting the solidification fluid, preferably the solidification gas. Solidification then proceeds to step c3').

[0091] Preferably, contact with the solidification fluid, preferably the solidification gas, is maintained until the block has completely solidified.

[0092] After complete solidification, a block is obtained which, after steps d) and possibly e) and f), gives a powder of particles of the molten product according to the invention.

[0093] In the optional step d), the molten product obtained is crushed and / or ground so as to reduce the size of the pieces, preferably until a powder of molten particles is obtained having a median size D50 preferably greater than 0.2 pm, preferably greater than 0.5 pm and / or, preferably, less than 50 pm, preferably less than 30 pm, preferably less than 10 pm, preferably less than 5 pm, preferably less than 3 pm, preferably less than 1 pm, preferably less than 0.7 pm.

[0094] All types of crushers and grinders can be used to reduce the size of the pieces, the grinding preferably being carried out dry and / or in a solvent, preferably water. An attrition mill, an air jet mill or a ball mill are well suited.

[0095] In one embodiment, the product obtained after crushing is de-ironed, according to any technique known to a person skilled in the art.

[0096] The molten particle powder may also undergo, particularly after step d), a further step intended to form agglomerates or aggregates. All techniques known to those skilled in the art may be used, in particular atomization of a slip or granulation.

[0097] In step e), which is optional, a particle size selection is then carried out, depending on the intended application, for example by sieving or cycloning.

[0098] In one embodiment, the process according to the invention comprises steps d) and e).

[0099] In step f), which is optional, a heat treatment of said molten product is then carried out.

[0100] Advantageously, step f) makes it possible in particular to reduce the amount of crystallized phase of (monoclinic zirconia + monoclinic hafnia) in the molten product according to the invention.

[0101] The molten product, preferably in the form of particles, is introduced into a furnace to be annealed.

[0102] The annealing temperature is lower than the melting temperature of the molten product and preferably above 800°C, preferably above 900°C and preferably below 1400°C, preferably below 1300°C, preferably less than 1200°C, preferably less than 1150°C, preferably less than 1100°C. The duration of the holding period at the annealing temperature is preferably greater than 2 hours and / or preferably, less than 24 hours.

[0103] Preferably, the molten product is annealed under an atmosphere containing a gas having an oxygen volume content greater than 20%, preferably air.

[0104] When the process includes a step f), the melted product according to the invention can be ground and / or undergo a particle size selection step, before and / or after said step f).

[0105] In one embodiment, the process according to the invention comprises steps d) and f). Preferably, in said embodiment, step f) is carried out, then step d).

[0106] In one embodiment, the process according to the invention comprises steps d), e) and f), said steps being able to be carried out in any order, step f) being for example before step d). Preferably, in said embodiment, a step f) is carried out, then a step d), then a step e). Examples

[0107] The following non-limiting examples are given for the purpose of illustrating the invention. Measurement protocols

[0108] The following measurement protocols were used to determine certain properties of the molten products.

[0109] The chemical analysis of the product of Example 1, carried out after drying at 80°C for 12 hours, is measured by inductively coupled plasma spectrometry (ICP) for elements whose content does not exceed 0.5%. To determine the content of the other elements, the product to be analyzed is dried at 80°C for 12 hours, then a bead of said product to be analyzed is produced by melting, and then the chemical analysis is carried out by X-ray fluorescence.

[0110] The possible carbon and sulfur contents are measured using a CS744 model carbon-sulfur analyzer, marketed by the company LECO.

[0111] The median size of a powder is classically measured using a Partica LA-950V2 laser particle size analyzer marketed by the company Horiba.

[0112] For each example, the quantity of (monoclinic zirconia + monoclinic hafnia), in mass percentages based on the total mass of the crystallized phases of zirconia and hafnia of the powder of the example, is determined by X-ray diffraction, after said powder has been deagglomerated using an agate mortar.

[0113] The diffraction pattern is acquired using a Bruker D8 Endeavor instrument, over an angular range of 20° between 5° and 100°, with a step size of 0.01° and a counting time of 0.34 s / step. The front optics include a 0.3° primary slit and a 2.5° Soller slit. The sample is rotating on itself at a speed of 5 rpm, with use of the automatic knife. The rear optics have a 2.5° Soller slit, a 0.0125 mm nickel filter and a 1D detector with an aperture of 4°.

[0114] The diffraction diagrams are then qualitatively analyzed using EVA software and the PDF-5+ 2024 database.

[0115] Once the phases present have been identified, the diffraction diagrams are analyzed, using the HighScore Plus software from Malvern Panalytical, according to a Rietveld refinement with the following strategy: - Define the background noise so that it is indistinguishable from the signal in areas without diffraction peaks. - select the previously determined background noise using "use available background", - Import the PDF sheets of the identified phases and select "Spherical Harmonies" for each phase in the preferred orientations, - Select the "Automatic (Default Rielveld)" mode and start the refinement process. - switch to manual mode, and for each phase whose quantity is greater than 1% by mass and simultaneously: - in "spherical harmonies", select all the coefficients, and restart the refinement, then - select "U", and restart the refinement, then - select "V", and restart the refinement, then - select "Peak Shape 1", and restart the refinement, then - select "Peak Shape 2" and restart the refinement, then - select "Peak Shape 3", and restart the refinement, then - select "B Overall" from all phases simultaneously, and restart the refinement, then - select "Atomic coordinates", "Occupancy" on all atoms of the phases, and restart the refinement.

[0116] The average size of zirconia crystallites, D, of the powders in the examples is classically determined by X-ray diffraction on said powders using a Bruker D8 Endeavor type apparatus, with the following Debye-Scherrer equation: 2) — ...........x _L x - K being equal to 0.89, cost? 10 - X being the wavelength of X-rays, here equal to that of copper, i.e. 1.5418 Angstroms, - B being the full width at half maximum of the zirconia peak present at 20° equal to 50°, in degrees - b being the full width at half maximum of the peak located at 20 equals 35° of a LaB6 standard, reference NIST 660a, analyzed under the same conditions as the sample, and - 20 being the angle of maximum intensity of the zirconia peak present at 20 equals 50°, in degrees.

[0117] The acquisition of the diffraction diagrams of the standard in LaB6 and of each example is carried out, under the same conditions as for the measurement of the quantity of (monoclinic zirconia + monoclinic hafnia).

[0118] The full width at half maximum (FWHM) of the zirconia peak at 20° = 50° of the example sample is determined as follows. On the diffraction pattern, an area containing the peak located at 20° = 50° is selected, taking care that said area also includes a portion of the baseline and that said area does not contain any other peaks. After eliminating the Ka2 line, the width of the zirconia peak at 20° = 50° is conventionally determined using the Highscore + software from Malvern Panalytical, by inserting a peak using the "Insert peak" function at 20° = 50°, and then performing automatic refinement using the "Default Profile Fit" function with a pseudo-Voigt function with a "split width" asymmetry. The full width at half maximum of the peak present on the diffraction diagram at 20 equals 50°, B, is the value of the parameter (“total FWHM”).

[0119] For the LaB6 standard, the full width at half maximum of the peak located at 20 equals 35°, b, is determined following the same procedure.

[0120] The average size of zirconia crystallites is then calculated using the Debye-Scherrer equation described above.

[0121] For example 1, the PDF sheets used for the measurements of the quantity of (monoclinic zirconia + monoclinic hafnia) and for the measurements of the average size of zirconia crystallites are sheets 04-014-8566 and 04-014-8565. Manufacturing protocol

[0122] The molten product of Example 1 was prepared from the following raw materials: - zirconia powder with a purity greater than 99.9% by mass, and with a median size of 15 pm; - Scandium oxide powder of purity greater than 99.9% by mass, and having a median size less than 40 pm.

[0123] The molten product of Example 1 was prepared according to a manufacturing process according to the invention: a) mixing the raw materials to form a starting charge; b) melting said starting charge in a single-phase Héroult-type electric arc furnace with graphite electrodes, with a furnace chamber 0.8 m in diameter, a voltage of 160 V, current of 1500 A and specific electrical energy supplied of 2500 kWh / T loaded; cl') pouring the molten material into a graphite mold; c2') solidification by cooling of the molten material poured into the mold until a block is obtained that is at least partially solidified; c3') demolding of the block; d) Crushing of the block obtained at the end of step c), then grinding in a jar using zirconia balls containing 3% MgO by mass, followed by attrition grinding in a LabStar mill marketed by Netzsch, for 7 hours, of an aqueous suspension consisting of 4000 grams of the powder obtained after jar grinding, 1600 grams of Zirmil® Y beads with a median size of 1.25 mm, marketed by Saint-Gobain ZIRPRO, and 5000 grams of demineralized water. After attrition grinding, the resulting suspension is oven-dried at 80°C for 12 hours to obtain a powder. This powder is then deagglomerated using an agate mortar.

[0124] The following table 1 provides the mass composition of the starting charge.

[0125] [Tables 1] Raw materials % by mass Zirconia powder 93.3 Scandium oxide powder 6.7

[0126] The following Table 2 provides the characterizations obtained on the molten particle powder obtained, MnO, Pr2O3, Nd2O5 and Tb4O7 expressing the total contents of manganese, praseodymium, neodymium and terbium oxides, respectively.

[0127] [Tables2] Example 1 Chemical analysis, in mass percentages based on the mass of the product (ZrO2+HfO2) + Sc2O3 + Y2O3 + A12O3 + CeO2 + Yb2O3 + Gd2O3 + MnO + Bi2O3 + La2O3 + Pr2O3 + Nd2O5 + Sm2O3 + Eu2O3 + Tb4O7 complement to 100% of which Sc2O3 6.2 Constituents other than ZrO2, HfO2, Sc2O3, Y2O3, A12O3, CeO2, Yb2O3, Gd2O3, MnO, Bi2O3, La2O3, Pr2O3, Nd2O5, Sm2O3, Eu2O3, and Tb4O7 0.25 Subscripts x and y defining the molar proportions of the constituents in the formula (Sc2O3)y(A) x (ZrO 2+HfO 2 ) ixy X 0.000 y 0.056 1-xy 0.944 Other characteristics (monoclinic zirconia + monoclinic hafnia), as a percentage by mass based on the crystallized phases of zirconia and hafnia 20 Average size of zirconia crystallites (nm) 7 Dio (pm) 0.22 D50 (pm) 0.53 D90 (pm) 0.90

[0128] The powder of example 1 then underwent a step f) of heat treatment of annealing under air at 1100°C with a 4-hour rest at this temperature.

[0129] The powder obtained at the end of step f) has an average size of zirconia crystallites equal to 16 nm and a mass amount of (monoclinic zirconia + monoclinic hafnia) equal to 4%, based on the crystallized phases of zirconia and hafnia.

[0130] As is now clear, the invention provides a fused product of scandiated zirconia, manufactured according to a simple melting process.

[0131] Of course, the present invention is not limited to the embodiments described, which are provided by way of illustrative and non-limiting examples.

[0132] In particular, the molten product according to the invention is not limited to particular shapes or dimensions.

Claims

Demands

1. Polycrystalline molten product of formula (Sc2O3)yAx(ZrO2 + HfO2)ixy, with 0.030 < y < 0.150, and 0.00 < x < 0.070, and x < y, A denoting an additive selected from Y2O3, Al2O3, CeO2, Yb2O3, Gd2O3, MnO, Bi2O3, La2O3, Pr2O3, Nd2O5, Sm2O3, Eu2O3, Tb4O7 and mixtures thereof, ZrO2 + HfO2 + Sc2O3 + A representing more than 98% of the mass of said molten product, MnO expressing the total content of manganese oxides expressed as MnO, Pr2O3 expressing the total content of praseodymium oxides expressed as Pr2O3, Nd2O5 expressing the total content of neodymium oxides expressed as Nd2O5, Tb4O7 expressing the total content of terbium oxides expressed as Tb4O7.

2. Molten product according to the immediately preceding claim, wherein the additive is selected from A12O3, CeO2, Yb2O3 and mixtures thereof, preferably from A12O3, CeO2 and mixtures thereof, preferably is CeO2.

3. Product melted according to any one of the preceding claims comprising, in mass percentages on the basis of the crystallized phases of zirconia and hafnia, an amount of (monoclinic zirconia + monoclinic hafnia) less than or equal to 30%, preferably less than or equal to 10%.

4. Product melted according to any one of the preceding claims in the form of a particle having a sphericity greater than 0.

8.

5. Product melted according to any one of the preceding claims, wherein 0.130 > y > 0.040 and / or x < 0.

050.

6. Product melted according to the immediately preceding claim, wherein 0.110 > y > 0.050 and / or x < 0.

030.

7. Product melted according to the immediately preceding claim, in which x < 0.

015.

8. Product melted according to any one of the preceding claims, wherein y = 0.060 or y = 0.

100.

9. Product melted according to any one of the preceding claims, wherein - x = 0.000 or wherein - x > 0.

005.

10. Product melted according to any one of the preceding claims, wherein x = 0.010 and the additive is CeO2 or is A12O3.

11. Product molten according to any one of the preceding claims, having an average zirconia crystallite size greater than or equal to 5 nm and less than or equal to 10 nm.

12. Powder comprising more than 90% by mass of particles in a molten product according to any one of the preceding claims.

13. Powder according to the immediately preceding claim, having a median size D50 greater than 0.2 pm and less than 50 pm.

14. Powder according to the immediately preceding claim, having a median size D50 of less than 1 pm.

15. Electrode or electrolyte comprising a molten product according to any one of claims 1 to 11.

16. Electrode or electrolyte according to the immediately preceding claim, obtained by sintering a particulate mixture comprising a powder according to any one of claims 12 to 14.

17. Solid oxide electrochemical device comprising an electrode, in particular an anode, and / or an electrolyte according to any one of the two immediately preceding claims.

18. A manufacturing process comprising the following steps: a) mixing raw materials to form a starting charge; b) melting the starting charge until a molten material is obtained; c) cooling until complete solidification of said molten material, said starting charge being adapted, in step a), to obtain, at the end of step c) a melted product according to any one of claims 1 to 11; d) optionally, grinding said melted product, preferably until a powder is obtained;

19.

20. e) optionally, particle size selection of said melted product; f) before or after step d), optionally, annealing heat treatment of said melted product. Manufacturing method according to the immediately preceding claim, wherein in step a), the starting charge contains scandiated zirconia. Molten product obtained or capable of being obtained by a process according to either of the two immediately preceding claims.