Observation of the room-temperatureTe125Mössbauer effect inMg3TeO6: Linewidth, recoil-free fraction, and isomer shift

Fifty-eight-day ${}_{}{}^{125}{}_{}{}^{}\mathrm{Te}_{}^{\mathit{m}}{}_{}{}^{}$ in a ${\mathrm{Mg}}_3$ ${\mathrm{TeO}}_6$ host provides an easily produced, rugged, high recoil-free fraction and narrow-emission-linewidth source for ${}_{}{}^{125}{}_{}{}^{}\mathrm{Te}$ Mössbauer spectroscopy. The high f factor of this source opens the possibility of precision T-dependent Mössbauer-spectroscopy measurements in Te-bearing compounds with the source kept at room temperature. Using such a source at 300 K, we have measured the T dependence of the f factor for both ${\mathrm{Mg}}_3$ ${\mathrm{TeO}}_6$ and cubic ZnTe absorbers and find Debye temperatures ${\mathit{FTHETA}}_{\mathit{D}}$ of 390(2) K and 188(2) K, respectively. At 300 K, the f factor of ${\mathrm{Mg}}_3$ ${\mathrm{TeO}}_6$ (0.46) is found to be an order of magnitude larger than in cubic ZnTe (0.040) thus making feasible room-temperature observation of the Mössbauer effect with the oxide source. Both emission and absorption linewidths of the oxide matrix have been examined and display a 14(3)% line broadening over the natural width (${\mathrm{\Gamma }}_{\mathit{n}}$), a result that is thought to be intrinsic to the oxide host. The isomer shift of Te metal (78 K) and cubic ZnTe (78 K) relative to ${\mathrm{Mg}}_3$ ${\mathrm{TeO}}_6$ at 300 K is +1.86(9) and +1.21(3) mm/s, respectively. ${\mathrm{Mg}}_3$ ${\mathrm{TeO}}_6$ is easily prepared in a pure form and yields reproducible crystal structure and Mössbauer-effect parameters. ${\mathrm{Mg}}_3$ ${\mathrm{TeO}}_6$ provides a suitable standard matrix for ${}_{}{}^{125}{}_{}{}^{}\mathrm{Te}$ isomer shift and f-factor measurements.