Angle of polarization and refractive indices of BaTiO 3

Large variation is found in the reported values of the principal indices of BaTiO3. According to Wemple et al. and Johnston, n0 should be greater than 2.425 (λNa), whereas according to Lawless and DeVries and other workers it is of the order of 2.370. The methods employed by these workers involve the passage of light through the body of the crystal. We have used the phenomenon of polarization by reflection to determine these indices and have found n0 = 2.428 ± 0.002 and ne = 2.371 ± 0.0045, closely agreeing with the earlier workers. The method is described at length because it is not common. Its accuracy has been demonstrated by redetermining the principal indices of calcite.