Degradation of Electrical Conductivity in Lanthanum Silicate Oxyapatite

Abstract

Degradation of electrical conductivity in lanthanum silicate oxyapatite (La 9.33+x Si 6 O 26+1.5x ) was observed at 600~1000 o C. Small particles were detected on the surface of pellets after electrical conductivity measurements for 100~201 h. These particles were identified as La 2 SiO 5 phase using micro-Raman spectroscopy. Lanthanum content in the oxyapatite phase is strongly related to its conductivity, because the excess oxygen is incorporated by charge compensation according to excess lanthanum composition. This study suggests that the decrease in electrical conductivity may be attributed to reduction in electrical charge carriers as a result of the phase degradation of La 2 SiO 5 phase from oxyapatite phase.