Controlling dielectric properties of pyrochlore neodymium zirconate by substitution of rare earth ions

The influence of A-site substitution in pyrochlore-type neodymium zirconate with smaller rare earth ions on dielectric properties was investigated.First-principles calculations for [Nd 16 Zr 16 O 56 ] and [Nd 15 MZr 16 O 56 ] (M = Sm, Gd, Y, Er, or Sc) predicted that Gd, Y, and Er have two types of six equivalent stable positions displaced from the original Nd position, generating a dipole moment.In addition, the energy barrier between these stable positions is below 10 -2 eV, suggesting a potential enhancement of the dielectric constant.To validate the impact of substitution on dielectric properties, (Nd 1-x Gd x ) 2 Zr 2 O 7 (NGZO, x = 0.00, 0.25, 0.50, 0.75, 1.00) and (Nd 1-x Er x ) 2 Zr 2 O 7 (NEZO, x = 0.00, 0.15, 0.25, 0.50, 0.75, 1.00) were synthesized using the solid-state reaction method.X-ray diffraction confirmed the pyrochlore structure for NGZO (except at x = 1.00) and NEZO (for x 0.25).The lattice constant followed Vegard's law within the compositional range of the pyrochlore phase.The dielectric constant slightly increased with increasing x (0.25) in NGZO, implying the contribution of dipole moments between Gd and its surrounding O ions.