Floor tile question

[pdqtom]

I am gathering materials to build a 42" oven and have come across used "floor tiles" from a commercial pottery kiln. These are actually High temp shelves used in the kiln and I can get them reasonably priced. They are approx. 1" thick and 20" square. Are these acceptable for "flooring" in the oven. I was going to use firebrick but came across these. They are much thinner than using firebrick, should I use one layer or perhaps two or stick with the firebrick?

This forum is awesome, by reading it I now know too much and need to stop researching and start building!