JaguarJoe, I didn't even know that about PZT materials until you mentioned it, I looked it up and there's a good reason; most commonly used PZT material in electronics tends to be Quartz, and that has a Currie temperature of 573 degree's C, so it's not a worry.
I'm a little fuzzy on the specifics but the reason the change occurs is because at those temperatures the crystal structure changes which causes the loss of polarization. Something you might want to look into a little more, because I haven't (in the few minutes I spent) read anything that suggests that the material won't repolarize when it's cooled back down.
Like hardening of metals if you heat it up fast and snap cool it it may not be okay, but if you heat it up beyond the Currie point and allow it to cool very gradually the original crystaline structure should reform, but this being a ceramic it may be slightly more complicated than that as I'm not familiar with the formation of LZT ceramics, metallurgy is only a hobby =) And one of my least knowledgeable ones.
As long as you don't exceed the Currie temperature; and you have a healthy margin of error by the looks of it no damage can possibly occur anyways. I would mostly avoid thermal shock by making sure that cooling is gradual.