Bi-apatite: Synthesis, crystal structure and low-temperature heat capacity

作者：Bulanov E N^*; Korshak K S; Lelet M I; Knyazev A V; Baikie T

来源：Journal of Chemical Thermodynamics, 2018, 124: 74-78.

DOI：10.1016/j.jct.2018.04.021

• Apatite
• Synthesis
• Heat capacity
• Thermodynamic functions
• In situ thermoXRD

In the present study, we describe a new approach to the synthesis of a Bi-containing apatite, which allows for a reduced reaction time and temperature. Using in-situ variable temperature X-ray diffraction measurements, we have refined the crystal structure of the material, which shows that its composition may be described as [Ca3.88 +/- 0.01Bi0.12 +/- 0.01](F)[Ca4.42 +/- 0.01Bi1.58 +/- 0.01](T)(PO4)(6)O-1.85 +/- 0.01. The compound displays isotropic thermal expansion in the temperature range (173-373) K. A thermodynamic investigation of the sample was undertaken, which revealed the low-temperature heat capacity, C-p,m(o), which was determined using adiabatic calorimetry from T = 6.4 K to 305.0 K. Smoothed C-p,m(o)(T) values between 6.5 K and 305.0 K are presented, along with the functions [S-m(o)(T) - S-m(o)(6.5)], [H-m(o)(T) -H-m(o)(6.5)], and [Phi(o)(m)(T) - Phi(o)(m)(6.5)]. Possible causes of the abnormal increase on the heat capacity curve in the lowtemperature region are discussed.

• 出版日期2018-9
• 单位南阳理工学院