Thermodynamic and thermophysics properties of synthetic britholite SrPr4(SiO4)3O

Crystal Chemical Substitution at Ca and La Sites in CaLa4(SiO4)3O To Design the Composition Ca1–xMxLa4-xREx(SiO4)3O for Nuclear Waste Immobilization and Its Influence on the Thermal Expansion Behavior

“…Similar reports are available in the literature with the complete substitution of RE 3+ ions such as Pr 3+ and Sm 3+ in systems such as CaPr 4 (SiO 4 ) 3 O and CaSm 4 (SiO 4 ) 3 O, showing marked decrease in the thermal expansion coefficient in the temperature range 298–1173 K . Similarly, thermal expansion coefficients of the oxyapatite of the formula SrPr 4 (SiO 4 ) 3 O are determined to be α a = 10 × 10 –6 K –1 and α c = 6.7 × 10 –6 K –1 at temperatures between 173 and 1173 K. On the other hand, partial substitution of Ca 2+ by Sr 2+ and Pb 2+ as shown in Ca 0.8 Sr 0.1 Pb 0.1 La 3.4 ­Ce 0.1 Pr 0.1 Nd 0.1 Sm 0.1 ­Gd 0.1 Y 0.1 (SiO 4 ) 3 O leads to a significant increase in the thermal expansion coefficient values α′ a = 11.74 × 10 –6 K –1 and α′ c = 11.70 × 10 –6 K –1 in comparison to those of CLSI. Such an observation of an increment in CTE has been reported in the oxyapatite La 9 ASi 6 O 26.5 with an increase in ionic radii of substituting divalent ions A = Ca 2+ → Sr 2+ → Ba 2+ .…”

“…42 The values are significantly low in comparison to the rare earth containing phosphate−silicate apatite Ca 9 Nd(PO 4 ) 5 (SiO 4 )F 2 , whose average thermal expansion coefficient is reported to be 21 × 10 −6 K −1 in the temperature range 20−1000 °C. 43 The compilation of the CTE values of various oxyapatites (Table 3) 16,17,21,22 shows that the thermal expansion coefficients of the current systems are comparable.…”

“…In the family of apatites, the thermal expansion behavior of oxysilicates such as X 9.33 (SiO 4 ) 6 O 2 (X = La, Nd), La 9 ASi 6 O 26.5 (A = Ca, Sr, Ba), CaLn 4 (SiO 4 ) 3 O (Ln = Pr, Sm, Eu), Y 4.69 (SiO 4 ) 3 O, Ca 6 Th 4 (SiO 4 ) 3 O, La 10 Si 6– x Cu x O 27 , and SrPr 4 (SiO 4 ) 3 O has been reported. Literature on oxysilicates of the formulas Ca 3.05 Ce 2.38 ­Fe 0.25 Gd 5.37 ­Si 4.88 O 26 and Ca 3.78 La 0.95 ­Ce 1.45 Zr 0.78 Fe 0.14 ­Nd 2.15 Eu 0.50 ­Si 6.02 O 26 as wasteforms is available .…”

Ceramic Mineral Waste-Forms for Nuclear Waste Immobilization

“…15. Britholite (silicate apatite; also known as oxy-apatite in the literature) [3,46,51,239,240,241,242,243,244,245,246,247,248,249], Figure 15.…”