Microwave Dielectric Properties of N${\mathrm{H}}_4$${\mathrm{H}}_2$P${\mathrm{O}}_4$, and Partially Deuterated K${\mathrm{H}}_2$P${\mathrm{O}}_4$

The temperature dependence of the complex dielectric constants at 9.2 Gc/sec are reported for a series of partially deuterated potassium dihydrogen phosphate crystals as well as for a potassium dihydrogen arsenate and an ammonium dihydrogen phosphate crystal. The transition temperature, the high-temperature loss tangent, and the temperature-independent ratio $tan\frac{{\delta }_c}{\epsilon _c^{}{}_{}{}^{\prime }}$ all increase monotonically with increasing deuteration. Proton tunneling in the four symmetry coordinates, which describe displacements along the four hydrogen bonds in the primitive cell, is considered briefly.