Electrical and optical properties of CaCu3Ti4O12 (CCTO) substrates for microwave devices and antennas

Abstract

The solid-state procedure is used to produce bulk ceramics of CCTO (CaCu3Ti4O12). The samples of the CCTO ceramic are studied by X-ray powder diffraction and infrared and Raman scattering spectroscopy. The infrared and Roman scattering spectroscopy confirm the formation of the CCTO phase, as seen by X-ray diffraction (XRD) analysis. One experimental procedure uses an organic binder in the process of shaping the samples. In the second procedure, the samples were prepared without the presence of the organic phase, and we obtained a higher dielectric constant (K = 7370) with higher loss (D = 0.2) at 1 KHz. For the first procedure, a lower dielectric constant (K = 1530) and lower loss (D = 0.11) at 1 KHz were obtained. Simple rectangular antenna prototypes were also designed on substrate samples (C1, C2, P1, and P2). For the antennas with P2, C1, and C2 as substrates, the bandwidth (BW) is 90 MHz (around 3%). The antenna with P1 substrate presents a surprisingly high BW of 270 MHz, which corresponds to a 10% bandwidth. Such a value is in accordance with the requirements for planar antennas in a variety of wireless communication systems such as WLAN, PCS, Wi-Fi, and other protocols. Therefore, these measurements confirm the potential use of such materials for small high-dielectric planar antennas (HDAs). These materials are also attractive for capacitor applications as well as for microelectronics and microwave devices (cellular mobile phones, for example), where miniaturization of the devices is crucial.