There is a need for low dielectric, low loss ceramic substrates for microwave electronics. Earlier works report rare earth dopants are very much useful to control the dielectric properties of sintered ceramics. This paper describes the effect of Gd2O3 and Pr2O6 rare earth co-dopants on the dielectric properties of MgO-doped alumina ceramics. Sintering, microstructures and the dielectric properties are investigated and reported. First of all, ultrafine alumina particles were obtained by ball milling which were converted to sintered alumina ceramics at temperatures 1400, 1450, 1500 and 1550°C. Sintered α -Al2O3 ceramics showed nearly 70% theoretical sintered density at 1450 °C which was increased beyond 97% at 1550 °C. The SEM micro-structure images reveal the presence of elongated, spherical like Al2O3 grains in the sintered samples. The results on dielectric constant (ε r), dielectric loss and a.c. resistivity indicate that sintered MgO doped alumina ceramics have low dielectric constant in the range ε r <6 in presence of Gd2O3 and Pr2O6 co dopants which is one order less than the phase pure Al2O3 ceramics. The dielectric constant decreases with the increase in MgO. The resistivity of sintered alumina increases with increase in dopant concentration and decreases with increase in temperature. High vacancy concentration at the interfaces of GPMDA and Al2O3 phases is possibly responsible for the resistivity of G-P co doped Al2O3 ceramics. The fine grain microstructure of sintered alumina creates more interfaces which in turn responsible for the dielectric constant 4.9 to 8.7 for doped alumina at the frequency of 1 MHz.
|Número de páginas||11|
|Publicación||Optoelectronics and Advanced Materials, Rapid Communications|
|Estado||Publicada - 2013|
|Publicado de forma externa||Sí|