1. Luminescence and Solid-State Ionics Laboratory Department of Physics Bharathiar University Coimbatore 641046 Tamilnadu India
2. Materials Research Centre Department of Physics Nallamuthu Gounder Mahalingam College Bharathiar University Pollachi 642001 Tamilnadu India
3. Department of Inorganic Chemistry University of Chemistry and Technology (UCT) Prauge Technicka 5, Pin 16628, Prauge-6 Czech Republic, Europe