Thermal stability, electronic polarisability and optical basicity of ternary tellurite glasses

Thermal resistance against crystallisation, electronic polarisabilities and optical basicities of ternary tellurite glasses of R2O-R'O-TeO2 (R=Li, Na, K, R'=Mg, Ba, Zn, TeO2=70, 80 mol%) having a high potential as new, optica l functional glasses are examined from differential thermal analyses, densi ty and refractive index measurements. Ternary tellurite glasses containing ZnO or both Li2O and BaO shoit, a high resistance against crystallisation. Large electronic polarisabilities of oxide ions of 2.1-2.4 Angstrom (3) and large optical basicities of 0.9-0.97 are obtained even in the ternary tell urite glasses. Correlation between experimental optical basicities Lambda ( n(o)) estimated using refractive index and theoretical optical basicity Lam bda (th) calculated using optical basicity values of each oxide is examined . It is proposed that the modified optical basicity value for TeO2 oxide, L ambda (TeO2)=0.93 gives a good agreement between Lambda (n(o)) and A(th). T he effect of glass structure (i.e. TeO4 and TeO3 network structural units) on the optical basicity of tellurite glasses and the validity of large elec tronic polarisabilities of oxide ions hare been discussed.