Synthesis, microstructure and microwave dielectric properties of CaMgLaTiO ceramics.

Chen, Guo-hua; Di, Jie-chang; Li, Ming; Reaney, Ian; Lei, Yan; Xu, Hua-rui; Zhou, Chang-rong; Jiang, Min-hong; Liu, Xin-yu

CaMgLaTiO ceramics were prepared by a solid state ceramic route for x = 0, 0.5, 1, 2, 3 and 4. The structure and microstructure of the ceramics were investigated using X-ray diffraction, scanning electron microscopy and energy dispersive X-ray spectroscopy. X-ray diffraction results show that the CaMgLaTiO adopts an orthorhombic crystal structure with no secondary phase observed for x from 0 to 0.5. Secondary phase, MgTiO occurs with further increasing doping level (1 ≤ x ≤ 3). When x = 4, mixture phases LaTiO, MgTiO and a trace of unknown phase coexist. CaLaTiO ceramic exhibits a relative permittivity (ε) ~ 65, quality factor ( Q × f) ~13,338 GHz (at ~4.75 GHz), and temperature coefficient of resonant frequency (τ) ~ 165 ppm/°C. The sintering temperature was distinctly reduced from 1,580 °C for x = 0 to 1,350 °C for x = 4. With increasing Mg content, ε and τ obviously decrease, while Q × f value initially decreases and then increases. The ceramic for x = 2 shows ε ~ 50, Q × f ~ 9,451 and τ ~ 62.5 ppm/°C. By the complete replacement of Ca with Mg, MgLaTiO ceramic sintered at 1,350 °C for 4 h combines a high dielectric permittivity (ε = 31), high quality factor ( Q × f ~ 15,021) and near-zero temperature coefficient of resonant frequency (τ ~ 4.0 ppm/°C). The materials are suitable for microwave applications.

MICROSTRUCTURE; DIELECTRIC devices; CERAMIC metals; SCANNING electron microscopy; X-ray spectroscopy

Journal of Materials Science: Materials in Electronics, 2012, Vol 23, Issue 3, p746

0957-4522

Academic Journal

10.1007/s10854-011-0483-x