Departamento de Química Inorgánica y Orgánica, Universitat Jaume I, Avda. Sos Baynat s/n, 12071 Castellón, Spain.
Inorg Chem. 2013 Feb 18;52(4):1729-36. doi: 10.1021/ic301156c. Epub 2013 Jan 29.
Oxygen-deficient tetragonal tungsten bronzes ceramics with general formula Ba(2)NdTi(2+x)Nb(3-x)O(15-x/2) (0 ≤ x ≤ 1) have been prepared by low temperature solvothermal synthesis with final firing of ceramics at 1100-1300 °C in air. Rietveld refinement of X-ray powder diffraction (XRD) and neutron powder diffraction (ND) data at room temperature of Ba(2)NdTi(3)Nb(2)O(14.5) shows that Ba and Nd are ordered on the 15-coordinate and 12-coordinate sites, respectively, Ti and Nb are disordered nonrandomly over the two octahedral sites, and oxygen vacancies locate preferentially in the coordination sphere of Nd and Ti/Nb(2) atoms. Variable frequency impedance measurements show that samples are poor electronic conductors with activation energies ∼0.8-1.7 eV, conductivities ∼1 × 10(-5) S cm(-1) at ∼725 °C and with some evidence of oxide ion conduction at high x values. Composition dependence of the dielectric properties shows a transition from classic ferroelectric behavior with Ba(2)NdTi(2)Nb(3)O(15) to a relaxor-like behavior with Ba(2)NdTi(3)Nb(2)O(14.5). At intermediate compositions, both a first-order phase transition and relaxor-like behavior are observed.
具有通式 Ba(2)NdTi(2+x)Nb(3-x)O(15-x/2)（0 ≤ x ≤ 1）的缺氧四方钨青铜陶瓷已通过低温溶剂热合成制备，最终在空气中于 1100-1300°C 下烧制陶瓷。室温下 Ba(2)NdTi(3)Nb(2)O(14.5)的 X 射线粉末衍射（XRD）和中子粉末衍射（ND）数据的 Rietveld 精修表明，Ba 和 Nd 分别有序占据 15 配位和 12 配位位，Ti 和 Nb 无序地占据两个八面体位，氧空位优先占据 Nd 和 Ti/Nb(2)原子的配位球。变频率阻抗测量表明，样品是电子不良导体，具有 ∼0.8-1.7 eV 的激活能，在 ∼725°C 时的电导率为 1×10(-5) S cm(-1)，在高 x 值时具有氧化物离子传导的一些证据。介电性能的组成依赖性显示出从具有 Ba(2)NdTi(2)Nb(3)O(15)的经典铁电行为到具有 Ba(2)NdTi(3)Nb(2)O(14.5)的弛豫体样行为的转变。在中间组成中，观察到一级相变和弛豫体样行为。
