Ultra-Low Thermal Expansion Ceramics

摘要

The crystal chemistry, synthesis, and thermal expansion investigation of NZP-family was completed--in that M superscript1Zr2P3O12 (M superscript1 = Li, Na, K, Rb, Cs), M superscript11Zr4P6O24 = Mg, Ca, Sr, Ba) and a few more compositions were studied. Single crystals of (NZP) and (CZP) were grown, and high-temperature x-ray measurements were made on these crystals to test the validity of a structural model to interpret thermal expansion data. The possibility of the development of a glass-ceramic of NaGe2P3O12 was explored. Dielectric measurements made on CaZr4P6O24 revela that in general (NZP)-materials have a low dielectric constant. Three new families, namely diborides (ZrB2, TiB2, and CrB2), Al2O3-GeO2 system and perovskite Pb(Mg1/3Nb2/3)O3 were investigated in order to search for any new low thermal expansion composition, but not much success was achieved in this direction, except that some perovskite compositions displayed low alpha behavior at low temperatures.