US-12623968-B2 - Functionally graded firing setters and process for manufacturing these setters

Abstract

A functionally graded firing setter that includes a substrate layer of cubic oxide; a top layer of unstabilized zirconium dioxide/hafnium dioxide; and a continuous transitional gradient layer disposed between the substrate layer and the top layer. The continuous transitional gradient layer includes cubic oxide stabilized zirconium dioxide/hafnium dioxide. The cubic oxide can be calcium oxide (CaO) or magnesium oxide (MgO).

Inventors

• Lucian Garrett Ferguson

Assignees

• Lucian Garrett Ferguson

Dates

Publication Date

20260512

Application Date

20221213

Claims (9)

1. 1 . A functionally graded firing setter comprising: a substrate layer consisting essentially of cubic oxide selected from a group consisting of calcium oxide (CaO), magnesium oxide (MgO), yttrium oxide (Y2O3), and cerium dioxide (CeO2); a top layer consisting essentially of unstabilized zirconium dioxide, unstabilized hafnium dioxide, or a combination thereof; and a continuous transitional gradient layer disposed between the substrate layer and the top layer, wherein the continuous transitional gradient layer comprises cubic oxide stabilized zirconium dioxide, cubic oxide stabilized hafnium dioxide, or a combination thereof, wherein the functionally graded firing setter are chemically non-reactive and peel resistant at temperatures of about 1650° C. in air atmospheres, wherein a surface of the firing setter consists of unstabilized zirconium dioxide, unstabilized hafnium dioxide, or a combination thereof, and is essentially free of alumina, stabilized zirconia, magnesia, and silicates.
2. 2 . The functionally graded firing setter according to claim 1 , wherein the cubic oxide is selected from a group consisting of calcium oxide (CaO) and magnesium oxide (MgO).
3. 3 . The functionally graded firing setter according to claim 1 , wherein the top layer is chemically bonded to the substrate layer through solid state reaction sintering.
4. 4 . The functionally graded firing setter according to claim 1 , wherein the cubic oxide is calcium oxide (CaO).
5. 5 . The functionally graded firing setter according to claim 1 , wherein the cubic oxide is magnesium oxide (MgO) and the continuous transitional gradient layer comprises 4-30 mol % MgO-stabilized zirconium dioxide and/or MgO stabilized hafnium dioxide.
6. 6 . A functionally graded firing setter prepared by a method comprising: preparing a first slurry consisting essentially of a cubic oxide selected from a group consisting of calcium oxide (CaO), magnesium oxide (MgO), yttrium oxide (Y2O3), and cerium dioxide (CeO2); preparing a second slurry consisting essentially of unstabilized zirconium dioxide, unstabilized hafnium dioxide, or a combination thereof; depositing the first slurry over a planar carrier; maintaining the first slurry deposited over the planar carrier for a predetermined duration; after the predetermined duration, depositing the second slurry over the maintained first slurry; upon depositing the second slurry, drying the deposited second slurry and the maintained first slurry; and upon drying, sintering the dried second slurry and the first slurry at a predetermined temperature range to obtain the functionally graded firing setter, wherein a surface of the firing setter consists of unstabilized zirconium dioxide, unstabilized hafnium dioxide, or a combination thereof, and is essentially free of alumina, stabilized zirconia, magnesia, and silicates.
7. 7 . The functionally graded firing setter according to claim 6 , wherein the cubic oxide is selected from a group consisting of calcium oxide (CaO) and magnesium oxide (MgO).
8. 8 . The functionally graded firing setter according to claim 6 , wherein the predetermined temperature range is about 1560° C. to 1650° C.
9. 9 . The functionally graded firing setter according to claim 6 , wherein the first slurry is deposited by tape casting, the first slurry is maintained for partially drying, and the second slurry is deposited by co-casting over the partially dried first slurry.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority from a U.S. Provisional Patent Appl. No. 63/298,613 filed on Jan. 11, 2022, which is incorporated herein by reference in its entirety. FIELD OF INVENTION The present invention relates to firing setters, and more particularly, the present invention relates to firing setters with improved stability and inertness, and a method of manufacturing these firing setters. BACKGROUND The devices or fixtures by which ceramic and metal components are physically supported during the process of heat treating or firing them are called “setters” or kiln furniture. Other well-known nomenclature that is used for various configurations and types of fixtures include saggers, refractory plates, and other varieties of trays or substrates with rails or sidewalls. The difficulties and challenges of heat treating or sintering reactive ceramic and metal materials are well known to persons skilled in the art. In a conventional production process, micron-sized reactive ceramic powders are mixed with an organic binder and then pressed, extruded, or tape cast to form “green” (unfired) components in the desired shape. The green component must then be heat treated at elevated temperatures to sinter or consolidate the component to the desired density and strength. The sintering process is typically performed with the green component placed in direct contact with a refractory plate or setter that must resist chemically reacting, sticking, or causing the component to crack and distort as it contracts and densifies. Thin green plates, membranes, and ceramic tapes are particularly difficult to sinter flat and distortion-free because they are exceptionally fragile and crack easily during the initial binder-burnout stages of firing. These components will often require an additional lightweight “cover plate” to keep them flat and prevent warping during firing. It is often desirable for the setter plates and cover plates to incorporate a certain amount of air porosity to allow gasses evolved from organic binders to escape without damaging the fragile green parts. There are numerous examples of firing setters that are made from a variety of ceramic materials, including alumina (Al2O3), alumino-silicates, mullite, silicon carbide (SiC), ytrria-stabilized zirconium dioxide (YSZ) and others, however alumina and alumino-silicate setters are most widely used industrially. Despite being an indispensable industrial component, the known setter materials have several limitation or drawbacks. For example, setters containing alumina or silica (SiO2) have adverse chemical reactions with many important technical materials including lithium-based solid electrolytes used in batteries, solid oxide fuel cell (SOFC) components that contain lanthanides and transition metals, nickel manganese compositions used in ferrites, piezoelectric ceramics and capacitors, dental zirconia, metal injection molded (MIM) compositions, and alloys that contain titanium or tungsten. Alumina-based setters also have poor thermal shock resistance and a tendency to exhibit excessive thermal creep or “slumping” at temperatures higher than about 1500° C., particularly in the porous form. Other conventional setter materials, such as silicon carbide and mullite have superior thermal creep resistance, but they contain elevated levels of silicon, a reactive glass former, which can contaminate components and cause them to stick and crack during firing. Another type of conventional ceramic setter material, known as “stabilized” zirconium dioxide or zirconia, exhibits superior toughness and thermal shock resistance, but suffers from a lack of chemical inertness and tends to slump at temperatures above about 1100° C. Pure zirconium dioxide (ZrO2) undergoes a well-known phase transformation from the monoclinic phase (stable at room temperature) to tetragonal at about 1173° C., and then to cubic at about 2370° C., according to below scheme: monoclinic⁢ (1173⁢°⁢ C.)↔tetragonal⁢ (2370⁢°⁢ C.)↔cubic⁢ (2690⁢°⁢ C.)↔melt Pure ZrO2 typically has no practical application for producing ceramic components due to the crystallographic phase transitions, and large accompanying volume change, which occurs during temperature cycling. The crystallographic volume change creates severe mechanical stress leading to cracking and catastrophic failure of the ceramic component. The cubic crystal structure of ZrO2 can be made stable over a wider temperature range by the addition of different oxide compounds, which are termed “stabilizers”. The oxides most used to form stabilized zirconia are calcium oxide (CaO), magnesium oxide (MgO), and yttrium oxide (Y2O3). The minimum amount of yttrium oxide needed to stabilize ZrO2 is about 3-8 mole %, while the minimum amount of magnesium oxide is about 16-25 mole %, and the minimum amount of calcium oxide is about 16-30 mole %. The thermal coefficient of expansion (TCE) depends on the phase or stabiliza