Synthesis, structure, and properties of BIFENBVOX

Abstract

Solid solutions Bi 4 V 2-x Fe x/2 Nb x/2 O 11-δ (х=0.05-1.0) and Bi 4 V 2-х-y Fe x Nb y O 11-δ (with fixed x or y=0.2 and variable х or y=0.2-0.5 with step 0.1) were synthesized by the standard ceramic technology in the temperature range 773-1113 K and by mechanochemical activation method using Bi 2 O 3 , V 2 O 5 Fe 2 O 3 , and Nb 2 O 5 oxides as initial compounds. The formation of solid solutions was studied. Ranges of stability and temperature values of phase transitions for different polymorphous modifications were defined using dylatometric and thermo gravimetric studies. The morphology and the local chemical composition of the ceramic samples were studied. Samples with concentration of dopants x>0.3 contain two phases; both major and impurity phases are solid solutions of the BIFENBVOX type although the dopants atoms distribution between them is random. The thermal expansion coefficients (TEC) were measured. The electrical conductivity of ceramic samples was investigated in a wide range of temperatures. The highest conductivity values among the studied solid solutions are observed for the sample with a small amount of dopants x=0.25.