Platinum crucibles

Dear Dr Duax

I am using platinum crucibles in high temperature research and need answers to three questions.

1. I am using 250 ml and 500 ml platinum crucibles with lids. My work requires that the lids have a complete seal and be easy to remove while the material is very hot. After three or four uses the platinum of new crucibles deforms slightly and the seal of the lid is lost. Thus, I am looking for equipment and information on the technique to reshape the platinum crucible and the lid surface to restore the seal.

2. How does one fabricate new platinum crucibles with circular platinum sheet material? I need information on the equipment required or a company that could manufacture new crucibles.

3. Are there other materials for crucibles that are cheaper than platinum that could be used for high temperature crystal oxide research? The material must be corrosion resistant to PbO, PbF₂, and metal oxides (WO₃, MoO₃, Li₂O, etc.), be a good conductor of heat, and resist deformation at 1300 C.

Any information would be greatly appreciated. e-mail: fishknot@aol.com