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Home / Academics / Division of Math & Science / Faculty / Christopher Jones / Dissertation / Chapter 2-Section 2.2

2.2 Preparation of Bulk Ceramic Electrodes

The first step to preparing YBa2Cu3O7 bulk electrodes is to make ceramic pellets of cuprate material. Stoichiometric amounts, as seen in Table 2.1, of Y2O3, BaCO3, and CuO are mixed together with a small amount of acetone. The mixture is ground until dry. At this point a uniform gray mixture is produced. The mixture is then placed in an alumina crucible and heated in a box furnace to 905oC at 300oC/hr and held for ~12 hrs. The sample is then cooled to room temperature and ground into a fine powder. The sample is then heated one more time to 915oC at 300oC/hr and held for ~12 hrs. Again, the sample is cooled to room temperature and ground into a fine powder. The sample is then pressed into pellets. The pellets are placed on the backs of combustion boats and sintered in a box furnace. Here, the sample is heated to 935oC at 300oC/hr. and held for ~12 hrs. The pellets are then cooled to room temperature and placed in a tube furnace for oxygen annealing. The tube furnace is then connected to slow flowing oxygen and heated to 450oC at 300oC/hr. The pellets are held at 450oC for ~6 hrs. Then, the pellets are cooled slowly to room temperature at 30oC/hr. This final step adjusts the oxygen content of YBa2Cu3O7-x to its maximum value, with x~0.04. Other substitutions of YBa2Cu3O7 are prepared by similar procedures.


Precursors

# of moles of Precursors

Mass

Y2O3

1/2 mole

0.7903 grams

BaCO3

2 moles

2.3148 grams

CuO

3 moles

1.6705 grams

Table 2.1: Stoichiometric amounts of metal precursors are used to make the YBa2Cu3O7-x superconductor.

Following previously described methods,3 the superconductor pellets were then broken in half. As seen in Illustration 2.2, the top portion was painted with silver paint (SPI) and allowed to dry. Next, a wire was connected to the pellet by silver epoxy or silver paint. The ceramic electrode assembly was then placed in a plastic tube where it was filled with a mixture of Epon 828 epoxy resin (Shell) and metaphenylenediamine (Aldrich) curing agent (13% by weight). The mixture was cured overnight at 80oC. The electrode was then sanded down to the ceramic superconductor on a grinding wheel. Then, the electrode was resurfaced using coarse sand paper in an inert atmosphere glovebox just prior to use.

These are the steps that can be used for making a bulk superconductor electrode, where a) is 1/2 of ceramic pellet, b) is a pellet coated on one end with Ag paint, c) has a wire attached with Ag epoxy, d) has the pellet encapsulated in epoxy, and e) has the encapsulated electrode sanded down to expose the superconductor’s surface.

Illustration 2.2: These are the steps that can be used for making a bulk superconductor electrode, where a) is 1/2 of ceramic pellet, b) is a pellet coated on one end with Ag paint, c) has a wire attached with Ag epoxy, d) has the pellet encapsulated in epoxy, and e) has the encapsulated electrode sanded down to expose the superconductor’s surface.

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Updated on: April 15, 2010 8:26 PM