Mobility of Ion Carriers in Piezoelectric Li.sub.2B.sub.4O.sub.7 Crystals

Impedance measurements of a Li.sub.2B.sub.4O.sub.7 single crystal with Ag electrodes have been performed in the frequency range of 1-3 x 10.sup.7 Hz at room temperature. A Li.sub.2B.sub.4O.sub.7 crystal (sp. gr. I4.sub.1cd, Z = 8) has been oriented along the c crystallographic axis. Contributions from the crystal bulk and the crystal/electrode interface are distinguished from the impedance hodograph of the Ag|Li.sub.2B.sub.4O.sub.7|Ag system. The structural mechanism of lithium-ion transport in Li.sub.2B.sub.4O.sub.7 crystals is discussed. Through conduction [sigma].sub.dc = 2.3 x 10.sup.-9 S/cm, carrier (vacancy [Formula omitted]) mobility [mu].sub.mob = 6 x 10.sup.-10 cm.sup.2/(s V), and their concentration n.sub.mob = 2.4 x 10.sup.19 cm.sup.-3 (0.14% on the amount of lithium in the lattice) are calculated based on the electrical and structural data.