Capacitive Energy Storage at Cryogenic Temperatures.
Abstract
A Phase I research program on capacitive energy storage at liquid-nitrogen temperatures is reported. A composition in the cadmium-lead-niobate-tantalate family of ceramic ferroelectrics was chosen with a paraelectric to ferroelectric phase transition at 71 K (so-called CPN17 composition), and prototype multilayer capacitors (MLC's), 1 x 1 x 0.2 cc with 46 active layers, were fabricated for testing. Dielectric-constant, specific-heat, and electrocaloric data were measured on these MLC's in the range 77-100 K at electric fields up to 200 kV/cm. All the measured data can be explained and correlated very satisfactorily using a Ginzburg-Landau expansion of the free energy in combination with the TdS equation for dielectrics. Capacitive-energy-storage densities were computed from the measured electric-field dependence of the dielectric constant at 77 K using the Helmholtz integral. A state-switching phenomenon was observed. The zero-field specific heat of CPN17 is 0.15 J/g/K at 77 K and displays an excess specific heat centered around 82 K.
Document Details
- Document Type
- Technical Report
- Publication Date
- Feb 15, 1985
- Accession Number
- ADA154508
Entities
People
- C. F. Clark
- W. N. Lawless