Electrical conduction and diffusion studies in NH 4H 2PO 4 and KH 2PO 4 single crystals

Abstract

Electrical conduction (dc) studies are made with pure and cobalt(II)-doped single crystals of NH 4H 2PO 4 and KH 2PO 4. The effect of the dopant concentration on the enthalpy for the migration of protons and the enthalpy for the rotation of the H 2PO 4 group have been studied. It is suggested that proton migration occurs through a synchronous phosphate rotation mechanism. Tritium diffusion studies in KDP and 32PO 4 diffusion in ADP crystals have been made. The mechanisms for the conduction and diffusion processes are found to be different in nature. The distribution coefficients of Co(II) dopant in ADP (2.92 × 10 −3) and KDP (1.14 × 10 −3) are calculated. The following enthalpy values are obtained. KDP (eV) ADP (eV) Enthalpy for the migration of protons 0.01 ± 0.01 0.15 ± 0.02 Enthalpy for the rotation of phosphate group 0.71 ± 0.01 0.66 ± 0.01 Enthalpy for T-diffusion 0.14 ± 0.01 — Enthalpy for 32PO 4 diffusion — 0.24 ± 0.01