Study of the influence of uncontrolled impurities on the structural phase transition in GdFe$_3$(BO$_3$)$_4$ using Raman scattering

When obtaining single-crystal samples using the solution-melt method, the solvent can affect the composition of the grown crystals through the inclusion of uncontrolled impurities, which can significantly affect the properties of the compound. To study the effect of impurities on the structural phase transition in trigonal borate GdFe$_3$(BO$_3$)$_4$, the temperature evolution of the Raman spectra of three single-crystal samples of this compound grown from three different solvents based on Bi$_2$Mo$_3$O$_{12}$, K$_2$MoO$_4$ and Li$_2$WO$_4$ was investigated. It was shown that the structural transition temperature $T_\mathrm{S}$ of Bi-substituted GdFe$_3$(BO$_3$)$_4$ ($T_\mathrm{S}$ = 145 K) decreased relative to the impurity-free sample ($T_\mathrm{S}$ = 166 K). The inclusion of impurities from the solvent based on K$_2$MoO$_4$ does not affect the $T_\mathrm{S}$ temperature, but affects the nature of the phase transition. The analysis of the obtained results was performed jointly with the calculation of the lattice dynamics.