The protonic. beta. )double prime) aluminas: Preparation, stability, conductivity and structure: Final report, 1 March 1984-31 August 1986

Technical Report · Sat Mar 19 00:00:00 EST 1988

OSTI ID:5254049

Farrington, G C

The studies carried out under this contract investigated the preparation, thermal stability, conductivity, and structures of the various protonic beta aluminas. The following issues were addressed: (1) why does a mixed ammoniumhydronium composition form when sodium beta alumina undergoes ion exchange in ammonium nitrate and what determines the relative proportions of ammonium and hydronium ions in the structure; (2) what is the thermal stability of the compound; and (3) what is the conductivity of ammoniumhydronium beta alumina and how is it influenced by composition. Data demonstrate that composition, thermal stability, and ionic conductivity in ammoniumhydronium beta alumina are closely related. Proportions of ammonium and hydronium are variable and depend on the duration of the ion-exchange process. Eventually, however, a steady-state composition is achieved. This composition corresponds to a particular and rather elegant ordered arrangement of ammonium ions, hydronium ions, and vacancies in the structure. In addition and in contrast to previous work, we found that water and ammonia evolve from ammoniumhydronium beta alumina in discrete steps below 350)degree)C. Water is lost from the structure between 150 to 250)degree)C with an enthalpy of 10 kcalmole. The loss of ammonia occurs at 250 to 300)degree)C with an enthalpy of 19 kcalmole. Below 300)degree)C, the thermal decomposition of ammoniumhydronium beta alumina is reversible. The conductivity of single crystals of ammoniumhydronium beta alumina (steady-state composition) obeys an Arrhenius relationship below 200)degree)C with an activation energy of 0.26 eV (sigma = 10/sup )minus/3)(..cap omega..-cm)/sup )minus/1) at 25)degree)C). Thermal annealing at 280)degree)C causes the conductivity to fall into the range observed for samples of hydronium beta alumina. 14 refs., 10 figs., 1 tab

• Research Organization: Pennsylvania Univ., Philadelphia (USA). Dept. of Materials Science and Engineering
• DOE Contract Number: AC02-80ER10597
• OSTI ID: 5254049
• Report Number(s): DOE/ER/10597-1; ON: DE88008442
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ALUMINATES
IONIC CONDUCTIVITY
PYROLYSIS
STABILITY
SOLID ELECTROLYTES
AMMONIUM COMPOUNDS
AMMONIUM NITRATES
ANNEALING
BETA-W LATTICES
CHEMICAL PREPARATION
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
MONOCRYSTALS
PROGRESS REPORT
THERMODYNAMICS
ALUMINIUM COMPOUNDS
CRYSTAL LATTICES
CRYSTAL STRUCTURE
CRYSTALS
DECOMPOSITION
DOCUMENT TYPES
ELECTRIC CONDUCTIVITY
ELECTRICAL PROPERTIES
ELECTROLYTES
HEAT TREATMENTS
KINETICS
NITRATES
NITROGEN COMPOUNDS
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
REACTION KINETICS
SYNTHESIS
THERMOCHEMICAL PROCESSES
360603* - Materials- Properties
360602 - Other Materials- Structure & Phase Studies