HIGH-DIELECTRIC-CONSTANT MATERIALS AS CAPACITOR DIELECTRICS-A STUDY IN DIELECTRIC SPECTROSCOPY. Final Report. Technical Report No. 145
A fundamental study is presented comparing the electric properties for materials of "normal" dielectric constant (Al/sub 2/O/sub 3/ and MgTiO/sub 3/) with those of high dielectric constant (TiO/sub 2/, CaTiCO/sub 3/, SrTiO/sub 3/, STABa/sub 0.65Sr/sub 0.35/! STATiO/sub 3/, and BaTiO/sub 3/). Single crystals and ceramics, as far as available, were investigated from d-c to the microwave range as function of time, temperature, field strength, and prehistory. Three types of relaxation spectra were identified, one caused by dipolar groups in unequal double wells, the other two by charge carriers stopped in the volume of the material or in front of the electrodes, respectively, O-H groups in rutile, identiffed by infrared absorption, seem to cause a dipolar spectrum by thermal excitation leading to hydrogen-bond formation. The shielding of dipoles by countercharges (dipole halos) is probably responsible for the unequal potential wells and likely to be a phenomenon of general importance. Electrons can be injected into rutile and other titanates by field emission. Parallel to the optic axis of rutile, the conduction currents reach especially high values because of an unhampered Ti/sup 3+/ yields Ti/sup 4+/ exchange, and thermal breakdown by field-emission currents occurs. Pure titania materials at high temperatures become very lossy because of thermal electron activation from O/sup 2/- to Ti/sup 4+/ The nonilear response characteristics of BaTiO/sub 3/ and lectric and paraelectric range and the onset of ferroelectricity for data are given for ceramics, and impulse and d-c strength measurements on rutile single crystals parallel and perpendicular to the axis. Voids, visible in x-ray micrographs. keep the breakdown strength of sintered ceramics relatively low; conduction holds the electric strength of rutile crystals in d-c tests to low values. Titanate ceramics at present allow an increase of storage density of capacitors by a factor of 5 to 10, a gain not attractive in view of the tively low, conduction holds the electric strength of rutile crystals in d-c tests to low values. Titanate ceramics at present allow an increase of storage density of capacitors by a factor of 5 to 10, a gain not attractive in view of the difficulties involved; a factor 10/sup 3/ might be realizable in the not too distant future. (auth)
- Research Organization:
- Massachusetts Inst. of Tech., Cambridge. Lab. for Insulation Research
- DOE Contract Number:
- AT(30-1)-1937
- NSA Number:
- NSA-14-008731
- OSTI ID:
- 4167239
- Report Number(s):
- AECU-4458
- Resource Relation:
- Other Information: Orig. Receipt Date: 31-DEC-60
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ABSORPTION
ACTIVATION
ALUMINUM OXIDES
BARIUM OXIDES
BREAKDOWN
CALCIUM OXIDES
CAPACITORS
CARRIERS
CERAMICS
CONFIGURATION
CRYOGENICS
CURRENTS
DEFECTS
DEFORMATION
DIELECTRICS
DIPOLES
ELECTRIC CONDUCTIVITY
ELECTRIC FIELDS
ELECTRIC POTENTIAL
ELECTRIC PROPERTIES
ELECTRICITY
ELECTRODES
ELECTRONS
EMISSION
EXCITATION
FERROELECTRIC MATERIALS
FERROMAGNETIC MATERIALS
HIGH TEMPERATURE
HYDROGEN
HYDROXIDES
IMPURITIES
INFRARED RADIATION
LIGHT
LOW TEMPERATURE
MAGNESIUM OXIDES
MEASURED VALUES
MICROWAVES
MONOCRYSTALS
PHOTOGRAPHY
PULSES
RUTILE
SINTERED MATERIALS
STRONTIUM OXIDES
TEMPERATURE
TESTING
TITANIUM OXIDES
X