X-Ray Diffraction and PVA treatment

6/23 AM
Today, with much anticipation, we removed the sample from the furnace that had ramped back down to room temperature. There was a distinct color change from gray to black. The samples had the appearance of looking like pellets of charcoal. We now have a superconductor! But we have to test it first.

The purity of the now superconductor was to be tested using an X-Ray diffractometer (pictured at right). Before this could be done, the pellets needed to be re-ground using the agate mortar and pestle. Once again, curses to the hunter-gatherers that creating these tools. They are definitely useful, but wholly uninteresting and an unending test of sanity. I found that as a tried to grind with more force, or more quickly, I was more likely to have product fly our of the mortar. This kept me in a perpetual state of wanting to do something faster than was prudent due to our desire to maximize product--rather than have it littered all over the lab tables.

The freshly ground powder was set in a diffraction slide-- a specially designed slide that looks like a thick microscope coverslip that was a rectangular depression in the middle (pictured at left). We were given a quick tutorial on how to use the diffractometer, a device with plenty of detail and chances to mess up the reading. But essentially, the instrument shoots an x-ray at the sample, and results in series of peaks. Those peaks are compared to a reference, and the percent alignment corresponds to the purity of our sample. Fortunately, the sample was relatively pure, with only a few errant peaks. Those should go away with the post-annealing process.

After lunch, we treated the sample with poly-vinyl alcohol. This will reduce electrostatic repulsions at the atomic level, allowing the substance to form a more dense pellet. The end result will be a more uniformly distributed lattice, that should more effectively show the Meissner effect (magnetic levitation).

We made a 3% by mass solution of poly-vinyl alcohol in de-ionized water. Solubility was low, and the solution did not readily form. We added two drops of the solution per gram to the sample that was now in a mortar. To aid the slurry formation, more DI was added to the mortar and the pestle was used to homogenize the mixture. It made a black mud along the surface of the mortar.

The mortar, containing the sample was placed in a 60 degree oven to dry overnight.

All-in-all, this day was mostly preparative in nature. It was nice to see that we had in fact made the compound that we were shooting for, even if the synthesis is relatively error-proof.