Applications for low temperature co-fired ceramics (LTCC) and high temperature co-fired ceramics (HTCC) are advancing to higher frequencies. In order to design ceramic microsystems and electronic packages, the electrical properties of materials must be well characterized over a broad frequency range. In this study, the dielectric properties of commercial Aluminum Oxide (Al 2O3) with different glass loadings have been characterized using three different measurement techniques: the split-post cavity, terahertz (THz) time-domain spectroscopy, and Fourier transform infrared spectroscopy (FTIR). Specifically, the dielectric properties will be characterized from 10 GHz to infrared frequencies. A split-post cavity was employed for determination of dielectric properties in the 10 GHz range. A broadband terahertz (THz) spectroscopy technique was used to characterize the specimens using measured time-domain transmission data. The dielectric constant and loss were extracted from the sample's frequency-domain transmission characteristics, providing data between 100 GHz to 2 THz. Additionally, Fourier transform infrared spectroscopy (FTIR) was used to characterize the samples from ∼33 to 3300 cm-1 (∼ 1THz - 100 THz). The measurements from the three techniques are compared, and dielectric constant and loss data will be presented for commercial and experimental ceramic systems from 10 GHz to infrared frequencies.