EFFECT OF THE APPEARANCE OF ANOMALOUS PROPERTIES OF METALOXIDE FRAMEWORK COMPOUNDS DURING THEIR DOPING IN THE REGION OF LOW ALLOYING IMPURITY CONTENT

• Datum: 2025
• Hauptverfasser: Korduban, Oleksandr, Trachevskii, Volodymyr
• Format: Artikel
• Sprache: English
• Veröffentlicht: V.I.Vernadsky Institute of General and Inorganic Chemistry 2025
• Online Zugang: https://ucj.org.ua/index.php/journal/article/view/736
• Назва журналу: Ukrainian Chemistry Journal

Using the example of phosphate КTi2(PO4)3:Al3+ and ceramics  Pb0,95Sr0,05(Ti0,475Zr0,525):Fe2O3, the existence of the effect of the appearance of anomalous properties of oxide framework compounds upon their doping in the region of low doping impurity content was confirmed for the first time.The effect of the appearance of anoma­lous physicochemical properties in oxide framework compounds is due to the existence of the initial doping stage in the region of low n content, at which substitution during doping occurs in a non-major way due to the selective filling of the positions of the Ap+ cations in oxygen cavities with Mn+ cations: Mn+→Ap+ and the formation of a Mn+ sublattice in the main structure.As a result, due to the occurrence of internal stresses and distortion of the structural elements of the lattice in the framework compounds, anomalous physicochemical properties arise. With a further increase in the content of the alloying element, the main method of replacing the positions of Nk+ cations in the oxygen octahedra with Mn+ cations becomes dominant: Mn+→ Nk+, which is accompanied by the disappearance of internal stresses and the loss of anomalous properties of the compounds.The effect can be applied in practice for a wide range of oxide framework matrices with luminescent, magnetic, catalytic, ionic,piezoelectric, and ferroelectric properties.The effect of the anomalous influence of trace doping impurities on the electronic structure and properties of КTi2(PO4)3:Al3+crystals and piezo­ceramics Pb0,95Sr0,05(Ti0,475Zr0,525):Fe2O3 was first established by the methods of XPS and EPR. The dynamics of the change of Ti3+-, Ti4+-, Fe2+-, Fe3+-, states of  Pb0,95Sr0,05(Ti0,475Zr0,525):Fe2O3 and Ti3+-,Ti4+-, Al3+-, IK+-, IIK+- states of КTi2(PO4)3:Al3+are compared in the work [1]. A feature of the initial stage of doping is a significant change in the electronic structure of the compounds. The increase in lattice stresses during doping causes homolytic cleavage of the Ti - O bond with the formation of two types of paramagnetic centers: the radical anion РО42- and the cation Ti3+.Synthesis in a narrow concentration range of the first stage is a difficult task. With a low content of the alloying element Mn+, its local concentrations in a viscous melt solution can differ significantly. This is manifested by a change in the properties of the synthesized compounds due to the inclusion of the main substitution mechanism during doping, i.e. the appearance of aluminum ions in titanium positions. Therefore, the formation of an ideal Mn+ sublattice at the first stage of doping is limited by the processes of distribution of Mn+ ions in the volume of the melt solution. In the li­terature, the effect of the appearance of ano­malous properties of metal oxide framework compounds upon their doping in the region of low dopant content is absent, and the doping process is still considered as having only one general stage of compensatory substitution Mn++(m-n)А+→М m+.