Effects of Na~+, K~+ and B~(3+) Substitutions on the Electrical Properties of La_(10)Si_6O_(27) Ceramics

摘要

Doping of Na and K at La sites and of B at Si site in La_(10)Si_6O_(27) with oxyapatite structure and fabrication of their ceramics were made by solid-state reaction method. It was found that partial substitution of Na~+ and K~+ on La sites decreased the sinterability of the La_(10)Si_6O_(27) based ceramics, whereas partial substitution of B~(3+) on Si site imporved the sinterability. Na~+ and K~+ substitutions in La_(10-x)Na_xSi_6O_(27-x) and La_(10-x)K_xSi_6O_(27-x) were found to suppress second-phase La_2SiO_5 formation. La_(10)Si_(5.5)B_(0.5)O_(26.75) ceramic sintered at 1575°C showed the highest electrical conductivity at temperatures above 600°C among all the apatite ceramics evaluated. The electrical conductivities of La_(10)Si_(5.5)B_(0.5)O_(26.75) at 700°C and 800°C reported 0.011 and 0.024 S cm~(-1), respectively, which are superior or comparable to previous studies, and their activation energies for conduction were calculated to be 0.80 eV.