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<p>An aqueous tartaric acid-assisted sol–gel synthesis technique was successfully applied to prepare a homogeneous La–Mo–O tartrate gel precursor and to crystallize a single-phase nanocrystalline La<sub>2</sub>Mo<sub>2</sub>O<sub>9</sub> compound at a temperature of 1273&#xa0;K. X-ray diffraction (XRD) was employed to study the effect of lanthanum concentration (La<sub>2±x</sub>Mo<sub>2</sub>O<sub>9±3/2x</sub>) on the formation of the La<sub>2</sub>Mo<sub>2</sub>O<sub>9</sub> phase and the occurrence of impurity phases. Differential scanning calorimetry (DSC) revealed that the crystallization of lanthanum molybdate-side phases decreases the amount of the La<sub>2</sub>Mo<sub>2</sub>O<sub>9</sub> phase in the reaction mixture and the thermal effect of phase transition in the temperature range from 813 to 853&#xa0;K. The reduction in heat consumption during the reversible phase transition, observed during the cooling process of the ceramic, seems to be directly correlated with the incomplete transformation of the high-temperature cubic phase into the stable monoclinic modification under standard conditions. Meanwhile, the results obtained from Raman spectroscopy and photoluminescence analysis of the synthesized ceramic samples provided evidence for the formation of nanocrystalline complex oxides, with lanthanum and molybdate being the predominant constituent in the resulting ceramic mixture.</p>

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The effect of lanthanum content on the composition and phase transition characteristics of the multicomponent La2±xMo2O9±3/2x system

  • 期刊论文

  • 发表日期：

    2025年3月28日

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  • Artūras Žalga,
  • Giedrė Gaidamavičienė,
  • Edgars Elsts,
  • Jevgenijs Gabrusenoks,
  • Anatoli I. Popov

摘要

An aqueous tartaric acid-assisted sol–gel synthesis technique was successfully applied to prepare a homogeneous La–Mo–O tartrate gel precursor and to crystallize a single-phase nanocrystalline La2Mo2O9 compound at a temperature of 1273 K. X-ray diffraction (XRD) was employed to study the effect of lanthanum concentration (La2±xMo2O9±3/2x) on the formation of the La2Mo2O9 phase and the occurrence of impurity phases. Differential scanning calorimetry (DSC) revealed that the crystallization of lanthanum molybdate-side phases decreases the amount of the La2Mo2O9 phase in the reaction mixture and the thermal effect of phase transition in the temperature range from 813 to 853 K. The reduction in heat consumption during the reversible phase transition, observed during the cooling process of the ceramic, seems to be directly correlated with the incomplete transformation of the high-temperature cubic phase into the stable monoclinic modification under standard conditions. Meanwhile, the results obtained from Raman spectroscopy and photoluminescence analysis of the synthesized ceramic samples provided evidence for the formation of nanocrystalline complex oxides, with lanthanum and molybdate being the predominant constituent in the resulting ceramic mixture.