High-temperature heat capacity of YFe3(BO3)4

Crystal structure, phase transition and structural deformations in iron borate (Y0.95Bi0.05)Fe3(BO3)4in the temperature range 90–500 K

“…Temperature dependence of the number of reflections (systematic extinctions in space group R32) with I > 3(I), observed in the diffraction pattern of (Y 0.95 Bi 0.05 )Fe 3 (BO 3 ) 4 in the whole studied temperature range 90-500 K, and in the region of structural phase transition 350-380 K (insertion). Several temperatures defying the range of changes are shown in the graph in K. significant at 370 K, and we can consider T str ' 370 K. The found temperature of structural transition proved to be lower than the previously established T str values in studies where yttrium iron borate powder samples were prepared without Bi (Hinatsu et al, 2003) and where single crystals were grown from Bi 2 Mo 3 O 12 -based melts (Denisov et al, 2014). At the same time, the found T str is somewhat higher than the one reported by Fausti et al (2006), where single crystals were also grown from Bi 2 Mo 3 O 12 -based flux.…”

“…To study the structure of single crystals above and below phase transition temperatures assumed to be 350 K (Fausti et al, 2006), 401 K (Denisov et al, 2014) or 445 K (Hinatsu et al, 2003), we obtained a complete sets of X-ray diffraction data at 90, 295, 380 and 500 K using synchrotron radiation on a PILATUS@SNBL diffractometer with an Oxford Cryo-stream700+ temperature system at BM01 station of the European Synchrotron Radiation Facility (ESRF) (Dyadkin et al, 2016). A heating and cooling of the sample fixed on a glass filament was carried out using a laminar flow of nitrogen gas.…”

“…On the other hand, the appearance of new modes in the phonon spectrum of YFe 3 (BO 3 ) 4 at 350 K was also attributed to the appearance of a structural phase transition (Fausti et al, 2006). At the same time, the extremum on the temperature dependence of the heat capacity in YFe 3 (BO 3 ) 4 found at 401 K (Denisov et al, 2014) was also explained by the structural phase transition in the range 376-426 K.…”

“…Thus, the structural transition for the Y 0.5 Gd 0.5 Fe 3 (BO 3 ) 4 crystal [where the ionic radius r ion (Gd) = 0.938 Å for the VI coordination is larger than r ion (Y) = 0.9 Å for the VI coordination] is observed at T str = 234 K , i.e. higher than T str = 155 K in GdFe 3 (BO 3 ) 4 (Levitin et al, 2004;Fausti et al, 2006;Frolov et al, 2016) and lower than the T str in YFe 3 (BO 3 ) 4 (Hinatsu et al, 2003;Fausti et al, 2006;Denisov et al, 2014).…”

“…The temperature of the structural phase transition of yttrium iron borates was determined by several methods in several studies; however, the values found for T str are inconsistent: T str = 350 K (Fausti et al, 2006), 401 K (Denisov et al, 2014), and 445 K (Hinatsu et al, 2003). According to the results of thermogravimetric analysis in the 300-600 K range, the exothermic peak in polycrystalline YFe 3 (BO 3 ) 4 at 445 K was attributed to a structural phase transition (Hinatsu et al, 2003).…”