Synthesis and High-Temperature Heat Capacity of Dy2Ge2O7 and Ho2Ge2O7

Abstract

Поступила в редакцию Твердофазным синтезом из стехиометрических смесей Dy 2 O 3 (Ho 2 O 3) и GeO 2 получены соединения Dy 2 Ge 2 O 7 и Ho 2 Ge 2 O 7. Методом дифференциальной сканирующей калориметрии исследовано влияние температуры в интервале 350-1000 K на теплоемкость полученных германатов. На основании зависимости C p = f(T) рассчитаны их термодинамические свойства. Ключевые слова: твердофазный синтез, германаты диспрозия и гольмия дифференциальная сканирующая калориметрия, теплоемкость, термодинамические свойства ВВЕДЕНИЕ

Evaluation of thermodynamic properties of alkaline borogermanates and germanosilicates using the regression analysis method

“…A comparison of the heat capacity [18] of pure silicon oxides (44.42 J•K -1 •mol -1 ), boron (62.98 J•K -1 •mol -1 ) and germanium (51.95 J•K -1 •mol -1 ) with the corresponding coefficients in equations (12)(13)(14) shows good convergence between them. The heat capacities of pure lithium (54.25 J•K -1 •mol -1 ) and sodium (68.56 J•K -1 •mol -1 ) oxides are also quite close to the obtained coefficients.…”

“…An analysis of Eqs. (6)(7)(8)(9)(10)(11)(12)(13)(14) shows that the coefficients for the same alkali metal oxides differ for silicates, borates and germanates (Figures 2-3). It should be noted that the values of the coefficient bj depend not only on the type of alkali metal oxide, but also on the class of the compound.…”

“…The correlation coefficient, indicating the correctness of the calculation method, was > 0.99 for Eqs. (6)(7)(8)(9)(10)(11)(12)(13)(14). Standard error (SE) characterises the overall accuracy of the resulting equations.…”

“…Nevertheless, there is currently little thermodynamic data on germanates. However, several studies on the high temperature heat capacity of rare earth germanates are extant [13][14][15]. These compounds are very promising in practical terms due to their luminescent properties.…”

Robust spin-ice freezing in magnetically frustrated Ho2GexTi2−xO7pyrochlore

“…The pyrochlore oxide having a molecular formula of A 2 B 2 O 7 [A (rare earth) = Ho, Dy, Yb, Y, Gd, Er, Eu, Tm etc; B (transition metals) = Sn, Ge, Ti, Mo, Mn etc) [8][9][10][11][12][13][14][15] displays engrossing low-temperature spin dynamics; e.g. in Tb 2 Ti 2 O 7 spins remain dynamic till the lowest feasible temperature whereas Gd 2 Ti 2 O 7 presents simultaneous coexistence of paramagnetic (dynamic) and ordered spins.…”