Synthesis and characterization of cryogenic perovskite ceramics

This work is an investigation into the suitability of the complex perovskite ceramic systems Pb(Mg/sub 1-x/Ni/sub x/)/sub 1/3/Ta/sub 2/3/O/sub 3/, (PMNiTa), and Sr/sub 1-x/Ca/sub x/(Ni/sub 1/3/Ta/sub 2/3/)O/sub 3/, (SCNiTa), for use as an electrostrictive and thus smart material in cryogenic environments. Both systems have been synthesized via conventional mixed oxide, pressed into pellets, and fired at the appropriate temperatures. When x=0.2 the lead-based system has a perovskite yield of 95% with the remainder being a pyrochlore, Pb/sub 1.34/Ta/sub 2/O/sub 6.34/; dielectric measurements show an increase in the dielectric constant, K', with decreasing temperature down to -85/spl deg/C which agrees with previous work. When x=0.0 the Sr based system, Sr(Ni/sub 1/3/Ta/sub 2/3/)O/sub 3/, is pseudocubic and has a hexagonal superstructure with the values of the lattice constants being in agreement with previous work.