Synthesis, structure, and characteization of Ce_1-xA_xTiO₃ (0.0 ≤ x ≤ 0.8; a = Sr, Ba)

The investigation of the solid solution Ce_1-xA_xTiO₃ (A = Sr, Ba) was undertaken with the aim to understand the magnetic and electronic properties as a function of alkaline earth doping. The solid solutions Ce_1-xA_xTiO₃ (A = Sr, Ba; 0.0 ≤ x ≤ 0.8) have been prepared by arc melting stoichiometric amounts of CeTiO₃ and ATiO₃ under argon. Single-phase samples of Ce_1-xSr_xTiO₃ can be made for the entire stoichiometry range. However, there is phase separation in samples of Ce_1-xBa_xTiO₃ for high values of x. The polycrystalline samples have been characterized using microprobe, thermal gravimetric analysis, powder X-ray diffraction, Ce L-edge X-ray absorption fine structure, temperature- and field-dependent magnetization, and dc electrical resistivity. The Ce_1-xSr_xTiO₃ samples crystallize in the orthorhombic space groups Pbnm (x ≤ 0.4) and Ibmm (0.4 ≤ x ≤ 0.8). The Ce_1-xBa_xTiO₃ samples crystallize in the orthorhombic space groups Pbnm (x ≤ 0.2) and Ibmm (0.2 ≤ x ≤ 0.6). The Ce_0.2Ba_0.8TiO₃ sample is biphasic containing an orthorhombic phase (Ibmm) and a hexagonal BaTiO_3-x phase. Ce XANES (X-ray absorption near-edge structure) data show that in all samples the Ce valence is 3+. The samples Ce_1-xSr_xTiO₃ (x = 0.0, 0.2) exhibit a ferromagnetic component below 135 K due to coupling between Ce and Ti moments. The temperature dependent resistivity measurement on polycrystalline CeTiO₃ shows it to be a small gap (0.005 eV) semiconductor. The Ce_1-xSr_xTiO₃ samples are metallic up to x = 0.8 while the Ce_1-xBa_xTiO₃ samples are metallic for x = 0.2, 0.4.