Scholarlink

<p>Formulas of phosphates K<sub>5/3</sub>MgE<sub>4/3</sub>(PO<sub>4</sub>)<sub>3</sub> (E = Ti, Zr) have been designed from crystal-chemical positions, their synthesis has been carried out, thermal stability, thermal expansion and temperature dependence of heat capacity have been studied. The samples obtained were characterized by XRD, IR, TG-DSC, scanning electron microscopy and microprobe electron analysis. The crystal structure and unit cell parameters were obtained by powder X-ray diffraction with Rietveld calculations (langbeinite structure, sp. gr. <i>P</i>2<sub>1</sub>3). The isobaric heat capacities of K<sub>5/3</sub>MgZr<sub>4/3</sub>(PO<sub>4</sub>)<sub>3</sub> phosphate were measured from <i>T</i> = 5 to 365&#xa0;K by adiabatic vacuum calorimetry and the thermodynamic functions were calculated from the experimental data. An anomaly in the heat capacity curve was observed at T below 6&#xa0;K, the nature of which was explained by the magnetic disorder-order phase transition. In the temperature range of 298–1473&#xa0;K, no effects were observed in the TG-DSC curves, indicating the thermodynamic stability of the samples. A minimum thermal expansion value of 2.0‧10<sup>−6</sup>&#xa0;K<sup>−1</sup> was found for K<sub>5/3</sub>MgTi<sub>4/3</sub>(PO<sub>4</sub>)<sub>3</sub> in the 173–473&#xa0;K range. Due to the structural stability of langbeinite, wide range of ionic substitutions, thermal, radiation and chemical resistance to leaching under time-varying conditions, phosphates with such structure can be considered as environmentally safe ceramic matrices for nuclear waste immobilization.</p> Graphical abstract <p></p>

错误：搜索内容不能为空，请输入英文关键词
错误：关键词超出字数限制，请精简
高级检索

Experimental study of the thermal behavior of potassium-magnesium-zirconium(titanium) phosphates with the langbeinite structure

  • 期刊论文

  • 发表日期：

    2025年9月3日

查看全文
  • Vladimir I. Pet’kov,
  • Egor A. Piaterikov,
  • Natalia N. Smirnova,
  • Natalya S. Kulikova,
  • Alexey V. Markin

摘要

Formulas of phosphates K5/3MgE4/3(PO4)3 (E = Ti, Zr) have been designed from crystal-chemical positions, their synthesis has been carried out, thermal stability, thermal expansion and temperature dependence of heat capacity have been studied. The samples obtained were characterized by XRD, IR, TG-DSC, scanning electron microscopy and microprobe electron analysis. The crystal structure and unit cell parameters were obtained by powder X-ray diffraction with Rietveld calculations (langbeinite structure, sp. gr. P213). The isobaric heat capacities of K5/3MgZr4/3(PO4)3 phosphate were measured from T = 5 to 365 K by adiabatic vacuum calorimetry and the thermodynamic functions were calculated from the experimental data. An anomaly in the heat capacity curve was observed at T below 6 K, the nature of which was explained by the magnetic disorder-order phase transition. In the temperature range of 298–1473 K, no effects were observed in the TG-DSC curves, indicating the thermodynamic stability of the samples. A minimum thermal expansion value of 2.0‧10−6 K−1 was found for K5/3MgTi4/3(PO4)3 in the 173–473 K range. Due to the structural stability of langbeinite, wide range of ionic substitutions, thermal, radiation and chemical resistance to leaching under time-varying conditions, phosphates with such structure can be considered as environmentally safe ceramic matrices for nuclear waste immobilization.

Graphical abstract