[1] (Pb 1-x Bi x )(Ti 1-x Mn x )O 3 : Competing mechanism of Tetragonal-Cubic phase on A/B site modifications Arun Kumar Yadav 1 , Anita Verma 1 , Birender Singh 4 , Deepu Kumar 4 , Sunil Kumar 1 , Velaga Srihari 5 , Himanshu K. Poshwal 5 , Pradeep Kumar 4 , Shun-Wei Liu 3 , Sajal Biring 3* , Somaditya Sen 1,2,3* 1 Discipline of Metallurgy Engineering and Materials Science, Indian Institute of Technology Indore, Indore 453552, India 2 Department of Physics, Indian Institute of Technology Indore, Indore 453552, India 3 Electronic Engg., Ming Chi University of Technology, New Taipei City, Taiwan 4 School of Basic Sciences, Indian Institute of Technology Mandi, Mandi-175005, India 5 High Pressure & Synchrotron Radiation Physics Division, Bhabha Atomic Research Centre, 400085, Mumbai, India Abstract Structural, vibrational and dielectric properties of (Pb 1-x Bi x )(Ti 1-x Mn x )O 3 (PBTM) (0 ≤ x ≤ 0.50) polycrystalline ceramics have been examined as a function of temperature. Synchrotron- based powder x-ray diffraction was employed to confirm phase purity and crystal structure of samples. Tetragonality (c/a ratio) of the PBTM system exhibit an increase 1.065, 1.066 for x = 0.06 and 0.09 compositions respectively, compare to 1.064 for x = 0 sample. Curie point was found ~763 K and 773 K for x = 0.06 and 0.09 samples respectively. Though, tetragonality start to decreasing from samples with x ≥ 0.18, Curie point of the samples started decreasing for x ≥ 0.12. Temperature-dependent x-ray diffraction reveals the structural change from tetragonal to cubic structure. Unit cell volume was found to decrease with increasing temperature; indicate these materials are negative thermal expansion type until phase transition temperature, with negative thermal coefficients are -1.571*10 -5 /K, -2.44*10 -5 /K, and -5.025*10 -6 /K for x = 0, 0.06, and 0.09 samples respectively. Raman spectra showed softening of the transverse optical