Probing Oxygen Defects in Na 0.5 Bi 0.5 TiO 3 Ferroelectric by Micro‐Raman Spectroscopy (Phys. Status Solidi B 7/2018) - Selvamani, Rachna; Singh, Gurvinderjit; Sathe, Vasant; Tiwari, Vidya Sagar (physica status solidi (b), 2018)