ELECTRICAL-CONDUCTIVITY RELAXATION AND NUCLEAR-MAGNETIC-RESONANCE OF LI CONDUCTING LI0.5LA0.5TIO3

Lithium ionic conductivity of Li0.5La0.5TiO3 has been studied using nu clear magnetic resonance (NMR) and admittance spectroscopy (AS) techni ques. Spin-lattice relaxation and electrical conductivity relaxation a re well described in terms of stretched-exponential correlation functi ons in the time domain of the form phi(t) = exp(-(t/tau)(beta)), but s howing different relaxation times scales (tau(0) = 1.4 x 10(-11) s fro m NMR and tau(0) = 10(-14) s from AS), and activation energies (0.15 a nd 0.4 eV, respectively). Different beta exponents, 1 from spin lattic e relaxation and 0.4 from electric-field relaxation have been also ded uced. A microscopic activation energy for lithium motion of 0.15 eV is deduced from both techniques. Discrepancies between both techniques a re analyzed and discussed in terms of frequency-dependent correlation effects.