Change in the Decay Constant ofTc99min BaTiO3by the Ferroelectric Transition

The BaTi${\mathrm{O}}_3$ ceramic samples were prepared by sintering mixtures of BaC${\mathrm{O}}_3$, Ti${\mathrm{O}}_2$, and $\mathrm{Na}{}_{}{}^{99m}{}_{}{}^{}\mathrm{Tc}{\mathrm{O}}_4$ at 1400°C. In these samples ${}_{}{}^{99m}{}_{}{}^{}\mathrm{Tc}$ atoms are located at the lattice site of the Ti atoms in the BaTi${\mathrm{O}}_3$ crystals, where an intense internal electric field acts. The relative change in the decay rate of the 2.17-keV $E3\mathrm{}$ isomeric transition of ${}_{}{}^{99m}{}_{}{}^{}\mathrm{Tc}$ embedded in BaTi${\mathrm{O}}_3$ in the ferroelectric state (at room temperature) and the paraelectric state (at 170°C) was measured. The result obtained is $\lambda$[$\mathrm{BaTi}\left({}_{}{}^{99m}{}_{}{}^{}\mathrm{Tc}\right){\mathrm{O}}_3$ in paraelectric state] $-\lambda$[$\mathrm{BaTi}\left({}_{}{}^{99m}{}_{}{}^{}\mathrm{Tc}\right){\mathrm{O}}_3$ in ferroelectric state] = $(2.6\mathrm{}\pm 0.4)\times {10}^{-3\mathrm{}}\lambda$[$\mathrm{BaTi}\left({}_{}{}^{99m}{}_{}{}^{}\mathrm{Tc}\right){\mathrm{O}}_3$ in ferroelectric state]. Statistics and errors of the measurement are discussed. It is reasonable to conclude that the main contribution to the observed effect comes from a change in the $4p$ electron density near the nucleus caused by the influence of the internal electric field in BaTi${\mathrm{O}}_3$.