Structural and dielectric properties of Ba5LnSn3Nb7O30 (Ln=La, Nd) ceramics
Abstract Two novel Ba 5 LnSn 3 Nb 7 O 30 (Ln=La, Nd) ceramics were prepared and characterized. Both compounds are paraelectric phases adopting the filled tetragonal tungsten bronze (TB) structure at room temperature. Ba 5 LaSn 3 Nb 7 O 30 and Ba 5 NdSn 3 Nb 7 O 30 ceramics show high dielectric constant of 171 and 182 together with low dielectric loss 1.2×10 -3 and 1.8×10 -3 at 1 MHz, respectively. In comparison with dielectric ceramics with TB structure in BaO–Ln 2 O 3 –TiO 2 –Ta 2 O 5 (Ln=La, Nd) system, the temperature coefficients of the dielectric constant ( τ e ) are significantly reduced.
We investigated the thermal stability of e-beam deposited Mo/B 4C/Si/B 4C layered systems, with and without ion assistance during the growth of the B 4C diffusion barrier layers. The thermal stability was investigated by in situ thermal annealing during grazing incidence X-ray reflection. By studying partially treated B 4C barrier layers, we found that the improvement in thermal stability is caused by an enhanced density of the B 4C layer. © 2012 American Institute of Physics.