Raman Scattering in Ionic Conducting Li2B4O7 Crystals at High Temperatures

Raman spectra of isotopically substituted Li2B4O7 (LB4) crystals have been measured within a wide temperature region (290–1040 K). Temperature dependences of the parameters of vibrational modes with participation of lithium ion have been analyzed. The character of temperature dependences of the frequency and the damping constant of these modes testifies disordering of lithium sublattice and a possibility of order-disorder phase transition in the vicinity of 750 K. Resonant and anharmonic interaction effects have been found to determine spectral intensity distribution in the Raman spectra of LB4 crystals at high temperatures. The possibility of appearance of lithium plasmon vibration in the Raman spectra has been discussed.