Synthesis and Crystal Structure of Cubic Perovskite-type BaMoxTi1−xO3 with x ≈ 0.175

Abstract

Single crystals of a novel solid-solution compound BaMo xTi 1¹x O 3 (x µ 0.175) in a BaTiO 3 and BaMoO 3 system were successfully grown by flux in Ar at 1423 K using the BaCO 3 B 2 O 3 system flux. The obtained crystals were black and rectangular with a maximum dimension of 0.2 © 0.2 © 0.3 mm 3 . The EDX and EPMA analyses confirmed the MoTi solid solution composition. Single-crystal X-ray structure analysis revealed the cubic perovskite structure, space group Pm 3m and the lattice parameters of a = 4.0112(6) ¡ and V = 64.54(3) ¡ 3 . The chemical composition and crystal structure were refined by the present structure refinement with the conventional values of R = 1.69% and wR = 1.89% using 156 independent observed reflections.Barium titanium oxide ceramics are important industrial materials. The perovskite BaTiO 3 and hexagonal BaTiO 3 have been extensively investigated because of their electric properties for use in dielectric and relaxor materials. 13 It is well-known that impurity or additive incorporation in BaTiO 3 in even quite small proportions may change the dielectric properties appreciably, e.g., Sb-doped BaTiO 3 4 and Ba 1¹x Na x Ti 1¹y Nb y O 3 . 5 On the other hand, perovskite BaMoO 3 is reported to be a good electrical conductor with resistivities in the range of 10100 ³ cm.6 However, substitution of titanium by molybdenum in BaTiO 3 has, to our knowledge, not been reported. In the present study, single crystals of the solid-solution compound BaMo xTi 1¹x O 3 with x µ 0.175 were successfully grown by flux, and the crystal structure was refined by single-crystal X-ray diffraction.Single crystals of BaMo x Ti 1¹x O 3 were synthesized by flux using a BaCO 3 B 2 O 3 system. The as-prepared Ba 2 Ti 13 O 22 powder 7 was mixed with BaCO 3 (99.9%) and B 2 O 3 (99.9%) in order to form a flux material with a nominal mass ratio of Ba 2 Ti 13 O 22 :BaCO 3 :B 2 O 3 = 1:5:5. The mixture was placed in Mo crucibles, heated in Ar at 1423 K for 10 h, and then cooled on standing. The products were easily separated from the frozen flux by rinsing the crucibles in hot water for several hours.The qualitative chemical composition of the products was investigated by scanning electron microscopyenergy dispersive X-ray analysis (SEM-EDX, JEOL JSM-5400) and electron probe microanalysis (EPMA, JEOL JXA-8100).Integrated intensity data were collected on a Rigaku AFC-7S four-circle diffractometer at 295 K using selected singlecrystal specimens. The electron density distribution was analyzed by the maximum entropy method (MEM) using the present single-crystal X-ray diffraction data with the PRIMA program. 8 The obtained three-dimensional electron density distributions were visualized with the VESTA program. 9Black single crystals of BaMo x Ti 1¹x O 3 with a maximum size of 0.2 © 0.2 © 0.3 mm 3 were grown in the frozen flux, as shown in Figure 1. The crystal surfaces were covered with the polycrystalline BaBO flux materials which were hardly removed by washing even using hot water. The good quality of the obtained rectangular cryst...