A cavity perturbation resonance technique suitable for microwave measurements on substrate materials is discussed. The technique makes use of thin rectangular samples placed in a rectangular waveguide cavity (Q∼5000). The availability of advanced microwave measurement equipment makes it possible to record experimental data at several frequencies (five in this present case). The estimated accuracy of measurements is ±2% for dielectric constant and 3×10−4 for dielectric loss. Results are reported in the 8.2–12.4-GHz frequency range for alumina and specially prepared silica.

The dielectric properties of ceramic lead zirconate and rutile are presented at microwave frequencies. Several techniques are required to span the frequency range from 100 Hz to 26 GHz, and rutile is utilized as a reference material to determine the consistency between measurement methods. A significant relaxation was seen for lead zirconate. At 10 GHz, the dielectric constant decreased 20% from the 1-MHz value of 160, and the dielectric loss increased by more than 3 times the lowfrequency value of 0.007.authors.'&'' One feature of the reviewed literature is the large variation of dielectric constants reported at room temperature (dielectric constants range from 62 to 110 at 1 MHz). This discrepancy gives strong evidence that consistent processing of PZ is difficult. In this study, the range of dielectric constant values between samples is 14%.

We reported the high quality semipolar (11‐22) GaN grown on m‐sapphire by using the novel two‐step growth method without low temperature GaN or AlN buffer layer. It is found that macroscopic surface morphology of semipolar GaN epilayer was very smooth, while microscopic surface structure was arrowhead‐like surface structure toward the direction of [1‐21‐1]. Anisotropic crystal properties of semipolar GaN/m‐sapphire were also observed by two incident directions of X‐ray beam. Therefore, we suggested that the anisotropic crystal properties and arrow‐head like surface structure would be caused by heteroepitaxial crystallograhpic difference between semipolar GaN and m‐sapphire. Additionally, photoluminescence (PL) measurements showed the strong bandedge emission of n‐type semipolar GaN without yellow luminescence (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

In this study, both commercial activated carbons (ACs) and chemically activated ACs were prepared and studied for the adsorption and desorption properties for volatile organic compounds (VOCs). The ACs with large surface areas have a high adsorption capacity for VOCs. However, their desorption efficiency is significantly low due to their complex pore structures and molecular size of VOCs. For enhancing the desorption rate, various in situ vacuum conditions (full vacuum, different pump speed and pressure, and vacuum with inflow) and the vacuum-heating combination system were applied. The desorption rate was observed to increase up to 40% under the condition where vacuum was supplied with inflow, and up to 85% in the combined system. In addition, the desorption mechanism operating in the vacuum condition was also studied.