Nature of V<SUP>n+</SUP> ions in SnO<SUB>2</SUB>: EPR and photoluminescence studies

SnO<SUB>2</SUB> and 5 at.% V doped SnO<SUB>2</SUB> samples were prepared by citrate-gel method. From Raman study on vanadium doped SnO<SUB>2</SUB>, the existence of phase separated V<SUB>2</SUB>O<SUB>5</SUB> clusters has been established. EPR study on the V doped sample clearly revealed the existence of V<SUP>4+</SUP> ions, which are incorporated in SnO<SUB>2</SUB> lattice and the existence of conduction electrons with g=1.993. For vanadium doped SnO<SUB>2</SUB> sample, there is a decrease in luminescence at 400 nm and an increase in activation energy of electrical conduction compared to undoped SnO<SUB>2</SUB>, and this has been attributed to the decrease in oxygen vacancies brought about by the incorporation of V<SUP>5+</SUP> in the SnO<SUB>2</SUB> lattice