Data Collection

The testing was conducted at Oak Ridge National Laboratory so we weren't able to take pictures of the data collection and experimentation process. The process was relatively simple, however, with the equipment at Oak Ridge. Samples of each pyrochlore were placed on different Pyrex curved glasses. One sample was placed in a furnace which was modified to have include a small hole at the top to allow a laser to shine on the sample in the furnace. We used a nitrogen laser operating at 337 nm to excite the phosphor in the furnace. A fiber-optic cable was used to carry the laser and position it properly and another directly next to it was used to carry the emissions from the phosphor away from the furnace. These light emissions from the pyrochlore were carried to a photomultiplier tube which work to detect the intensity of light over a certain period of time. The lifetime, or decay time, of the emissions from the pyrochlores was calculated by taking many measurements of the intensity of the emissions versus time at various temperatures. Finding the decay time for each pyrochlore at each temperature was the primary focus of this research. By calibrating the decay times for each temperature (i.e. this decay time corresponds to this temperature), the pyrochlores could be used as thermographic phosphors.

The graphs above are the decay time versus temperature for two of the pyrochlores that were tested. As seen, the decay time initially starts out relatively flat. In this flat range, the pyrochlores can't be used as thermographic phosphors because a specific decay time can't be assigned to a temperature. As the decay time starts to slope downward with temperature, the pyrochlores become usable as thermographic phosphor. For the compound in the first graph, lanthanum zirconate, this downward trends stops at approximately 800 degrees Celsius. At this point, the graph starts to flatten out again because the intensity of the emissions at this temperature are so low that change in decay time can not be calculated and roughly stays constant. This means that the pyrochlore can not be used as a thermographic phosphor at temperatures above that cutoff temperature where the graph starts to flatten out again. Optimally, we would have found a pyrochlore that sloped downward on this type of graph into temperatures well over 1200 degrees Celsius. The graphs show that lanthanum zirconate can be used to measure temperatures at higher temperatures than lanthanum hafnate which begins to show no change in decay time at approximately 600 degrees Celsius.