文摘
Compositions in the (1 − x)CaTiO3–xCa(Ta1/2Ga1/2)O3 (x = 0.4, 0.45, 0.50, 0.55) series were processed through a solid-state mixed-oxide route. X-ray diffraction (XRD) of x = 0.5 and 0.55 compositions revealed the formation of single-phase ceramics with orthorhombic (Pbnm) symmetry. At x ≤ 0.45, a couple of low intensity XRD peaks matching PDF# 04-002-5066 for Ca3TiTaGa3O12 were also observed which indicated second-phase formation. The microstructure of the sintered pellets for x = 0.5 and 0.55 compositions comprised densely packed irregular-shaped large grains with uniform contrast. The unit cell volume increased with increasing Ta5+ and Ga3+ contents at the B-site, which caused a decrease in both the relative permittivity (ε r) and temperature coefficient of resonance frequency (τ f) but an increase in quality factor (Q × f o). The optimum microwave dielectric properties (i.e., ε r ~ 47, Q × f o ~ 26,630 GHz and τ f ~ −2.64 ppm/ °C) were achieved for the x = 0.5 composition (i.e., CaTi0.5Ta0.25Ga0.25O3) which can be a potential candidate material for microwave dielectric applications. Thus, the substitution of Ta and Ga at the B-site of CaTiO3 was useful in tuning the larger positive τ f through zero and increasing Q × f o without too much compromise on ε r.