Temperature dependence of dielectric tangent loss in KDP and DKDP crystals at microwave frequencies

615-619<span style="font-size: 15.5pt;mso-bidi-font-size:8.5pt;font-family:" times="" new="" roman","serif""="">By adding cubic and quartic phonon anhannonic interactions in the pseudospin phonon coupled mode (PLCM ) model for KDP type crystals and using double -time temperature-dependent Green's function method, expressions for soft mode frequency, dielectric constant and dielectric tangent loss have been obtained. Using model parameters [<span style="font-size:14.5pt;mso-bidi-font-size:7.5pt; font-family:" times="" new="" roman","serif""="">PhysRev B, <span style="font-size:15.0pt;mso-bidi-font-size:8.0pt;font-family: " arial","sans-serif""="">21 <span style="font-size: 15.0pt;mso-bidi-font-size:8.0pt;font-family:" arial","sans-serif""="">(1980) 1933], the dielectric loses are calculated for KDP and DKDP crystals. In the microwave frequency range, an  increase in frequency is followed by an increase in dielectric tangent loss. The loss decrease with increase in temperature for KDP and DKDP crystals, respectively, in their para-electric phases. This shows Curie-Weiss behaviour or the dielectric <span style="font-size:15.5pt;mso-bidi-font-size:8.5pt;line-height:115%; font-family:" times="" new="" roman","serif";mso-fareast-font-family:"times="" roman";="" mso-fareast-theme-font:minor-fareast;mso-ansi-language:en-us;mso-fareast-language:="" en-us;mso-bidi-language:ar-sa"="">tangent loss.</span