The Mössbauer effect for ${\mathrm{Sn}}^{119m}$ in the PbZr${\mathrm{O}}_3$ lattice has been studied from 27 to 320 °C, with particular emphasis on the region near the Curie temperature. The Mössbauer fraction changes by (40 ± 8)% at the transition temperature $T_C$ from its value at room temperature. This is to be compared with the corresponding change of 10% for the earlier ferroelectric BaTi${\mathrm{O}}_3$: ${\mathrm{Sn}}^{119m}$ system. These results are consistent with Dvorak's suggestion that in antiferroelectrics the frequency over the entire optical branch may vanish at $T_C$. A sharp change in the isomer shift and the vanishing of the electric field gradient has also been observed, as is expected from the change in the crystal structure at $T_C$.

• Received 8 April 1970

DOI:https://doi.org/10.1103/PhysRevB.2.2756