Complex Dielectric Constant of KH2PO4at 9.2 Gc/sec

The temperature dependence of the dielectric constant and loss tangent in potassium dihydrogen phosphate along and normal to the optic axis has been measured by a cavity perturbation method at 9.2 Gc/sec. The dielectric constants agree with earlier low-frequency measurements. The parallel dielectric constant exhibits a modified Curie-Weiss behavior which may be described by $(T-T_c)\epsilon _c^{}{}_{}{}^{\prime }=A^{\prime }+BT$, with $T_c=119\mathrm{}$ °K, $A^{\prime }=2.27\mathrm{}\times {10}^3$ °K, $B=4.7\mathrm{}$. The parallel loss tangent also has an approximate Curie-Weiss dependence which may be described by $(T-T_c)tan{\delta }_c=\alpha +\beta T+\gamma T^2$, with $\alpha =8.42\mathrm{}\times {10}^{-1\mathrm{}}$ °K, $\beta =-9.49\mathrm{}\times {10}^{-4\mathrm{}}$, and $\gamma =8.49\mathrm{}\times {10}^{-6\mathrm{}}$ ${\left(\mathrm{°}\mathrm{K}\right)}^{-1\mathrm{}}$. This result is discussed in terms of Silverman's treatment of the microwave loss in strontium titanate. The implications of these measurements for microwave light modulation are also discussed.