Structural determination and microwave properties of (x)Re(Co1/2Ti1/2)O3-(1-x)CaTiO3 (Re = La and Nd) solid solutions

Solid solutions of (x)Re(Co1/2Ti1/2)O-3-(1 - X)CaTiO3 (Re = La and Nd, abbreviated to xLCT and xNCT, respectively) where x = 0, 0.25, 0.5, 0.75 and 1 have been fabricated using solid state synthesis. Samples have been examined using X-ray diffraction (XRD), scanning electron microscopy, transmission electron microscopy (TEM) and their dielectric properties measured at microwave (MW) frequencies. Formation of single phase solid solutions were confirmed by XRD and the measured lattice parameters varied linearly from LCT (a = 5.66 angstrom, b = 7.867 angstrom and c = 5.494 angstrom) and NCT (a = 5.636 angstrom, b = 7.914 angstrom and c = 5.461 angstrom) to CT (a = 5.596 angstrom, b = 7.731 angstrom and c = 5.424 angstrom). XRD and TEM confirmed both in-phase and antiphase rotations of O-octahedra consistent with an a(-)a(-)c(+) tilt system across the entire solid solution series. Electron diffraction revealed that LCT and NCT have reflections associated with B-site cation ordering which is absent for x <= 0.75. MW dielectric measurements showed that LCT and NCT were highly insulating with microwave quality factor (Qf(0)) values of 39,000 and 34,000, respectively. Compositions anticipated to have a zero temperature coefficient of resonant frequency (tau(f)) are 0.48LCT-CT and 0.52NCT-CT With epsilon(r) = 45 and Qf(0) - 5000 and epsilon(r) = 43 and Qf(0) - 4000, respectively. (c) 2004 Elsevier Ltd. All rights reserved.