Recently we found by muSR that the deuterium (D) atoms in the new ferroelectric compound Co2(OD)3Cl were quantum atomic and showed a critical slowing down with Tc=230 K, which leaded to a deuterium long-range order and brought out a ferroelectric transition at TE=230 K. Meanwhile in Co2(OH)3Cl, quantum atomic H showed Tc=210 K with incomplete ordering. For the first time, the muSR technique is successfully applied to ferroelectrics. The magnetic frustration seems also played a role in the critical slowing. Now we have lobserved similar ferroelectric behaviors in paratacamite Cu2(OD)3Cl/ Cu2(OH)3Cl, which has a similar highly symmetric R-3m structure like Co(OD)3Cl/ Co(OH)3Cl but has much different magnetism. The proposed experiment will contribute greatly toward the establishment of utilizing the muSR technique to ferroelectricity, which is one of the major solid-state physics field.