Methods of flash sintering
This disclosure provides methods of flash sintering and compositions created by these methods. Methods for sintering multilayered bodies are provided in which a sintered body is produced in less than one minute. In one aspect, each layer is of a different composition, and may be constituted wholly from a ceramic or from a combination of ceramic and metallic particles. When the body includes a layer of an anode composition, a layer of an electrolyte composition and a layer of a cathode composition, the sintered body can be used to produce a solid oxide fuel cell.
1. A method for sintering a multilayered body comprising a plurality of layers, the method comprising;
a) heating the body to a temperature ranging from 300 ° C. to 1300 ° C. while applying a DC, AC or pulsed electrical field ranging from 7.5 V/cm to 1000 V/cm with a power supply acting under voltage control to produce a non-linear increase in the conductivity of the body;
b) at the onset of the non-linear increase in the conductivity of the body, switching the power supply from voltage to current control, wherein the current limit is set such that the current density ranges from 1 mA mm −2 to 500 mA mm −2
wherein each layer of the body comprises ceramic particles and the combination of the non-linear increase in the conductivity of the body under voltage control and the subsequent switching of the power supply to current control produces a sintered body in less than one minute.
2. The method of claim 1 , wherein the multilayered body comprises at least one layer of a first composition and at least one layer of a second composition.
3. The method of claim 1 wherein each layer is porous prior to sintering and the initial average porosity of each layer are from 35 vol % to 60 vol %.
4. The method of claim 3 wherein the average porosity of at least one of the layers after sintering is from 0 vol % to 10 vol %.
5. The method of claim 3 , wherein the average porosity of at least one of the layers after sintering is from 30 vol % to 40 vol %.
6. The method of claim 1 wherein at least one layer of the body comprises from 95 wt % to 99.5 wt % ceramic particles and 0.5 wt % to 5 wt % binder prior to sintering.
7. The method of claim 1 wherein at least one layer of the body comprises from 95 wt % to 99.5 wt % of ceramic particles and metal particles and 0.5 wt % to 5 wt % binder prior to sintering.
8. The method of claim 7 wherein the amount of metal particles is greater than 0 and less than or equal to 40 wt %.
9. The method of claim 7 wherein the amount of ceramic particles is greater than or equal to 30 wt % and less than 100 wt %.
10. The method of claim 1 , wherein the multilayered material comprises from 2 to 50 layers.
11. The method of claim 10 , wherein the multilayered body further comprises at least one layer of a third composition.
12. The method of claim 11 , wherein the first composition is an anode composition, the second composition is an electrolyte composition, and the third composition is a cathode composition.
13. The method of claim 12 , wherein the multilayered body comprises a layer of the electrolyte composition located between a layer of the anode composition and a layer of the cathode composition.
14. The method of claim 13 , wherein the average porosity of the sintered layer of the electrolyte composition is from 0 vol % to 10 vol %.
15. The method of claim 13 , wherein the average porosity of the sintered layer of the anode composition is from 30 vol % to 40 vol %.
16. The method of claim 13 , wherein the average porosity of the sintered layer of the cathode composition is from 30 vol % to 40 vol %.
17. The method of claim 13 wherein the anode composition comprises yttria stabilized zirconia (YSZ) and at least one of nickel or nickel oxide.
18. The method of claim 13 , wherein the electrolyte composition comprises YSZ.
19. The method of claim 13 , wherein the cathode composition comprises strontium doped LaMnO 3 (LSM) or a composite of YSZ and LSM.
20. The method of claim 13 , wherein the temperature is from 300 ° C. to 1000° C.
21. The method of claim 13 , wherein the electrical field is from 20 V/cm to 600 V/cm.