Incipient ferroelectricity and microwave dielectric resonance properties of CaCu[sub 2.85]Mn[sub 0.15]Ti[sub 4]O[sub 12] ceramics

Mn-doped CaCu3Ti4O12 ceramics with nominal composition CaCu2.85Mn0.15Ti4O12 (CCMTO) have been prepared and their radio- and micro-wave dielectric properties established. At 300 K, dense CCMTO ceramics have appreciable grain resistivity, ∼20 MΩ cm, and exhibit microwave dielectric resonance with εr∼93, Qf∼3950 GHz (at 3.95 GHz) and temperature coefficient of resonant frequency ∼+657 ppm/K. εr decreases smoothly from ∼150 to 90 in the range of 10–300 K, obeys the Curie-Weiss law in the range of ∼60–180 K, and is consistent with incipient ferroelectricity. The source of the incipient ferroelectricity and potential applications of CCMTO ceramics are discussed.