Sintering, Microstructure, and Dielectric Properties of Copper Borates for High Frequency LTCC Applications.

New ceramic materials based on two copper borates, CuB2O4 and Cu3B2O6, were prepared via solid state synthesis and sintering, and characterized as promising candidates for low dielectric permittivity substrates for very high frequency circuits. The sintering behavior, composition, microstructure, and dielectric properties of the ceramics were investigated using a heating microscope, X-ray diffractometry, scanning electron microscopy, energy dispersive spectroscopy, and terahertz time domain spectroscopy. The studies revealed a low dielectric permittivity of 5.1-6.7 and low dielectric loss in the frequency range 0.14-0.7 THz. The copper borate-based materials, owing to a low sintering temperature of 900-960 °C, are suitable for LTCC (low temperature cofired ceramics) applications.