X-Ray Diffraction (XRD) Measurements on the Powders (Crushed Pellets) Were Carried Out

Electro-caloric effect in lead-free Sn doped BaTiO3 ceramics at room temperature and low applied fields

Sanjay Kumar Upadhyay1, V. Raghavendra Reddy1, Pallab Bag1 R Rawat1, S.M. Gupta2 and Ajay Gupta3

1UGC-DAE Consortium for Scientific Research, University Campus, Khandwa Road, Indore 452001, India.

2Ceramic Laboratory, LMDDD, RRCAT, Indore 452013, India

3Amity Center for Spintronic Materials, Amity University, Noida 201303, India.

X-ray diffraction (XRD) measurements on the powders (crushed pellets) were carried out using Bruker D8 Advance X-ray diffractometer equipped with 0.154 nm (Cu k-alpha) source and fast counting detector based on silicon strip technology (Bruker LynxEye detector). Figure-S1 shows the x-ray diffraction (XRD) data of all the samples(BaTi1-xSnxO3) fitted with Rietveld refinement using FullProf program [J. Rodryguez-Carvajal., Physica B 192, 55 (1993)]. No extra peaks are seen in the XRD data signifying the phase purity of the prepared samples. Right hand side of Figure show the enlarged view of XRD to depict the structural changes with Sn doping. One can clearly see the splitting of the peak at 2 =45o, which basically represents the tetragonality. This splitting is observed till x=5% whereas for the x=10% and 15% the splitting is merged into one peak corresponding to cubic (002) plane. Therefore, XRD data is fitted considering the tetragonal structure (P4mm space group) for x≤5% and for x≥10% considering the cubic structure (Pm3m space group). Also, one can see that there is a systematic shifting towards the lower angle with Sn doping, which can be understood based on the fact that the Sn+4 is larger than Ti+4 (rSn4+ ~ 69.0 pm, rTi4+ ~ 60.5 pm) [R. D. Shannon and C. T. Prewitt, Acta Crystallographica Section B-StructuralCrystallography and Crystal Chemistry B 26, 1046-& (1970)].

Scanning electron microscopy (SEM) measurements are carried out to study the microstructure of the samples and figure-S2 show the data. The grain size increased initially and grains as big as 50-70 μm are observed for x=5% sample in addition to some grains of about 1-2 μm indicating the bimodal grain size distribution. With further increase of Sn (≥ 10%) doping, the grain size decreased and for x=15% the grain size is similar to that of un-doped BTO. This is similar to the report of Cai et al., in which it is reported that decreasing grain size with increase of Sn doping is either due to more slow diffusing nature of Sn4+ ion (rSn4+ rTi4+) and / or Sn segregation at the grain boundary region and hence inhibiting the grain growth [J Mater Sci: Mater Electron 22, 265-272 (2011)].

Figure-S1: X-ray diffraction (XRD) data along with the Rietveld refinement of BaTi1−xSnxO3. Right frame show the splitting / Merging of the (002)/(200) peak as a function of Sn doping at Ti site

Figure-S2: Scanning electron micrographs of BaTi1−xSnxO3. Scale bar is 1μm for all the images