MICROSTRUCTURE AND IONIC TRANSPORT IN SINTERED NA BETA-ALUMINOGALLATES - A RADIO-WAVE AND MICROWAVE FREQUENCY DIELECTRIC STUDY

Sintered samples of beta-aluminogallates, Na1+x(Al0.5Ga0.5)(11) O17 x/2, have been synthesized and studied by high-frequency conductivity and dielectric spectroscopy in the broad frequency range 10(3) to 10(1 0) Hz. The dielectric measurements have been performed as a function o f temperature (290 to 420 K), porosity (18 to 50%) and sodium content y=1+x (1<y<1.5). For frequencies below 10(7) Hz, the complex resistivi ty plots have made it possible to determine the bulk de-conductivity o f beta-aluminogallates with respect to the sodium content by taking ac count of grain boundaries and porosity effects. For frequencies above 10(7) Hz, two types of dielectric relaxations corresponding to Na+ mot ions have been observed.