DETERMINATION OF LOW-FREQUENCY ELECTRO-OPTIC COEFFICIENTS OF NANO2

The unclamped electro-optic coefficients were measured in ferroelectric NaNO2. The following values were obtained at 150°C, in units of 10-10 cm/V: ra = r22 - (n3/n 2)3r32 = 4.1; rb = r32 - (n1/n3)3r12 = 4.2; rc = r22 - (n1/n2)3r12 = 0.6; r43 = - 1.9; r61 = - 3.0. The constants ra and rc vary approximately as ε2 does near the Curie temperature, as expected, but rb does not, decreasing toward zero at Tc. No significant temperature dependence was found in r61 or r43. The quantity ra changes sign as a function of temperature at 115°C. The observed behavior can be explained in terms of a temperature-independent response including both second- and fourth-order terms, biased by the spontaneous polarization. © 1969 The American Institute of Physics.