Preparation And Property Study Of New Na-doped Double Perovskites

Perovskite complex mental oxides have attracted more and more attention due to their complicated magnetic and electrical properties. In recent decades, various methods have been used to prepare A-doped or B-doped Perovskite complex metal oxides, such as conventional solid state reaction, sol-gel technique, hydrothermal technique, coprecipitation method, pulsed laser technique and self-propagating high-temperature synthesis. Many powder, film or single crystal materials were obtained by exchanging the doped element or varying the content of doped element in perovskite complex mental oxides. So far, however, there is not comprehensive conclusion about the physical and chemical properties of perovskite complex mental oxides, and some phenomenon is still in doubt. In view of the great value and study scope of these materials, more and more researchers are indulging in the study of perovskites.There are many new perovskites, double perovskites and their doped metal oxides, however, most of them are focused on the easily prepared oxides, such as manganese-based complex oxides and molybdenum-based complex oxides. The reports about difficultly prepared oxides are very rare. For example, due to the volatility of Na, there are little reports about Na-doped perovskites. It is difficult to obtain pure Fe(IV)-doped or Cr(IV)-doped perovskites, and the Fe(IV)-doped or Cr(IV)-doped perovskites are unstable, which makes people unwilling to study these oxides. In view of the reasons mentioned above, we have prepared eight Na-containing perovskite complex metal oxides through conventional solid state reaction. Besides, we introduce Fe(IV) or Cr(IV) into these Na-containing oxides, which are not reported previously.1. We have synthesized four novel double perovskites containing Na+ of LaNaFe(â…¢)TaO₆,LaNaFe(â…¢)NbO₆,LaNaMn(â…¢)TaO₆,LaNaMn(â…¢)NbO₆ through conventional solid state reaction. XRD analysis displays that all compounds have high degree of crystallization. SEM shows that the microstructure of these compounds is irregular, the crystalline grain exhibit different shape and dimension. TGA analysis displays all compounds are stable below 1000 oC at 10%H2-Ar atmosphere. Magnetic property test indicates that LaNaFe(â…¢)TaO₆ and LaNaFe(â…¢)NbO₆ contain weak ferromagnetic component,while LaNaMn(â…¢)TaO₆ and LaNaMn(â…¢)NbO₆ are soft magnets.2. With the goal of introducing Na+ and Fe⁴⁺ or Cr⁴⁺ into the same compound, we have synthesized four novel double perovskites of CaNaFe(IV)TaO₆,SrNaFe(IV)TaO₆,CaNaCr(IV)TaO₆,SrNaCr(IV)TaO₆. XRD analysis displays that all compounds have high degree of crystallization. SEM shows that the microstructure of CaNaFe(IV)TaO₆ and SrNaFe(IV)TaO₆ is non-uniform, the crystalline grain exhibit different shape and dimension, however, the crystalline grain of CaNaCr(IV)TaO₆ and SrNaCr(IV)TaO₆ exhibit regular shape and dimension. TGA analysis displays a loss-step is observed at high temperature under 10%H2-Ar atmosphere, which is attributed to the reduction of Fe⁴⁺ or Cr⁴⁺. Magnetic property study indicates that CaNaFe(IV)TaO₆, CaNaCr(IV)TaO₆ and SrNaCr(IV)TaO₆ are soft magnets, while SrNaFe(IV)TaO₆ is hard magnet..