STUDY ON ELASTIC, THERMODYNAMIC, AND OPTICAL PROPERTIES OF Y2TI2O7 PYROCHLORE DETERMINED BY A SEMI-EMPIRICAL METHOD AT 300 K

First-ever a straightforward semi-empirical method is employed to compute elastic parameters (elastic wave velocities, elastic moduli, Debye temperature), thermodynamic parameters (molar heat capacities at constant volume and pressure, Debye temperature, electronic contribution to molar heat capacity, lattice potential energy), and optical parameters (refractive index, optical energy bandgap, dielectric, electronic and ionic polarizabilities) for pyrochlore-type yttrium-titanate (Y2Ti2O7) at 300 K. The results of our calculations are compared with the existing experimentally and theoretically determined data. The quite satisfactory agreement between the two validates the approach adopted. The value of molar heat capacity at constant volume computed based on the Einstein theory for pyrochlore is accordant with theoretically predicted value from the law of Dulong and Petit while the Debye theory fails to estimate the consistent value at 300 K. It appeared that electronic molar heat capacity contributes ~ 0.5 % to the total molar heat capacity and the electronic and lattice molar heat capacities are comparable at 14.5 K. The applicability of the oxide additivity rule is examined and found successful in predicting the dielectric, electronic, ionic polarizabilities and lattice potential energy of the complex oxide composition. The semi-empirical method used in the present investigation is found quite simple as compared to previous cumbersome evaluation methods.