Stabilization and tunable microwave dielectric properties of the rutile polymorph in α-PbO2-type GaTaO4-based ceramics

摘要

The effects of Ti substitution on the crystal chemistry and microwave dielectric properties of Ga_(1-x)Ta_(1-x)Ti_(_(2x))O4 were investigated. GaTaO4 adopts a l:l-ordered monoclinic α-PbO2 type structure. At 1300 °C the Ga_(1-x)Ta_(1-x)Ti_(2x)O4 system formed a monoclinic α-PbO2 type solid solution when x ≤ 0.05, and further Ti substitution in Ga_(1-x)Ta_(1-x)Ti_(2x)O4 induced a phase transformation from α-PbO2 to rutile, leading to a rutile solid solution when x ≥ 0.15. Within the intermediate composition range 0.075 ≤ x ≤ 0.1, a mixture of α-PbO2 and rutile phases formed, which gradually transformed into a single rutile phase upon being fired at 1350-1400 °C. At 1400 °C the compositions where x = 0-0.025 remained in monoclinic α-PbO2 type phases, while the x = 0.05 composition transformed into a rutile polymorph, implying that Ti substitution is favorable for stabilizing the high temperature rutile polymorph of GaTaO4 down to room temperature.