Publications Repository - Gdańsk University of Technology

Tetragonal polymorph of lanthanum orthoniobate can be stabilized to room temperature by the substitution of Nb with an isovalent element. LaNb1-xAsxO4 (0 < x ≤ 0.3), where As is an element stabilizing tetragonal structure, were successfully synthesized with combined co-precipitation and solid-state reaction method. The phase transition temperature, above which the material has tetragonal structure, decreases linearly with increasing As-content, and LaNb0.7As0.3O4 is tetragonal at room temperature. The analysis of the influence of different isovalent substituents, namely V, Sb and Ta, has shown that there is a relation between the properties of the chemical element and its effect on the structure. It was proposed that the electronegativity of the substituent determines the type of stabilization – the tetragonal/monoclinic structure is stabilized by chemical elements with electronegativity higher/lower than that of niobium. The slope of the phase transition temperature dependence on the substituent content has been proposed as a parameter determining the “quality” of the stabilization, since steeper function leads to a larger decrease of transition temperature for the same content of different substituents. The analysis has shown that the stabilization of tetragonal structure, apart from the electronegativity, depends also on ionic radius of a substituent. Arsenic has been found to be a better stabilizer of the tetragonal polymorph of lanthanum orthoniobate than Sb, but worse than V.

Authors

• dr inż. Sebastian Lech Wachowski link open in new tab ,
• dr inż. Bartosz Kamecki link open in new tab ,
• dr inż. Piotr Winiarz link open in new tab ,
• dr inż. Kacper Dzierzgowski link open in new tab ,
• dr hab. inż. Aleksandra Dorota Mielewczyk-Gryń link open in new tab ,
• prof. dr hab. inż. Maria Gazda link open in new tab