The structure and dielectric properties of Ca1-xYx Ti1-xAlxO3 (CYTA) ceramics prepared by the mixed-oxide route have been investigated. CYTA forms a complete solid solution with an orthorhombic perovskite structure. Residual Y4Al2O2 and Y3Al5O12 resulting from incomplete reaction are observed for ≥ 0.9. Scanning electron microscopy shows that CYTA ceramics exhibit uniform microstructures, with an average grain size that decreases from ∼200 μm at x = 0 to ∼10 μm at x = 1.0. Transmission electron microscopy of CYTA (x = 0.3) ceramics reveals the presence of ferroelastic domains, and electron-diffraction patterns are indexed on the Pnma space group, consistent with an a+b-b- octahedral tilted structure. The relative permittivity, εr, decreases continuously from 170 to 12, while the microwave quality factor, Q·fr increases from 10,000 to 12,000 GHz, for x = 0 and 1, respectively. CYTA (x = ceramics exhibit εr ∼ 38, Q·fr of ∼14,212 GHz, and a temperature coefficient of resonance frequency, τf, of -14 ppm/°C. Small additions of acceptor (0.3 wt% ZnO) or donor (1 wt% Nb2O5) dopants decrease Q·fr by ∼20-30%, respectively. 0.30).
All Science Journal Classification (ASJC) codes
- Materials Science(all)
- Condensed Matter Physics
- Mechanics of Materials
- Mechanical Engineering