In this study, Pb(Ni_1/3Nb_2/3)O₃-Pb(Zr,Ti)O₃ ceramics substituted with Pb(Mg_1/2W_1/2)O₃ were fabricated with the variation of CuO for application to ultrasonic cleaning of removable orthodontic appliances (ROA). And their piezoelectric and dielectric properties were investigated. At the 0.12 wt% CuO added ceramics sintered at 930℃, the excellent values of dielectric constant=2,519, density=7.82 g/㎤, kp=0.64, d₃₃=536 pC/N, Qm=57 were obtained, respectively. These values were suitable for application to ultrasonic cleaning of ROA.

In this paper, for the application of ultrasonic cleaners for cleaning dentures and transparent braces, Pb(Mn_1/3Nb_2/3)O₃-Pb(Ni_1/3 Nb_2/3)O₃-Pb(Zr,Ti)O₃ [PMN-PNN-PZT] system ceramics were manufactured and their dielectric and piezoelectric properties were investigated. Overall the best properties suitable for the device applications such as ultrasonic cleaner were obtained from the ceramics sintered at 920℃: bulk density of 7.8 g/㎤, the dielectric constant (ε_r) of 1,689, piezoelectric charge constant (d₃₃) of 433 pC/N, planar electromechanical coupling factor (k_p) of 0.64, mechanical quality factor (Qm) of 835, S₁₁^E of 13.37 (10^-12 N/㎡), and Curie temperature of 315℃ By using the physical properties of this composition, the ultrasonic cleaner was designed and simulated using the commercial ATILA software. For the three-layered ceramics with the dimension of 25 mm × 25 mm × 2.5mm, an excellent displacement of 8.998 ×10^-3 m) and the sound pressure of 147.68 dB were recorded.

Phase evolution, sintering behavior, microstructure, and microwave dielectric properties of (1-x) mol Ba₃V₄O₁₃ - (x) mol BaV₂O₆ system were investigated. The sintered specimens of all compositions consisted of Ba₃V₄O₁₃ and BaV₂O₆, and no secondary phase was observed. As x increased, the linear shrinkage decreased to the composition of x=0.5, and then increased again, implying that Ba₃V₄O₁₃ and BaV₂O₆ phases interfered mutually with each other during sintering. All compositions showed a dense microstructure with a large grain growth. Cracks were observed in some compositions because of the relatively high sintering temperature of 620~640℃. As x increased, the dielectric constant increased, while the quality factor was maintained from about 50,000 GHz to about 70,000 GHz up to the composition of x=0.9, and then decreased to 20,987~27,180 GHz at the composition of x=1.0. As x increased, the temperature coefficient of the resonance frequency showed a (+) value from a (-) value. The dielectric constant, the quality factor, and the temperature coefficient of resonant frequency of x=0.7 composition sintered at 640℃ for 4 hours were 10.61, 71,126 GHz, and -4.9 ppm/℃, respectively. This composition showed a good chemical compatibility with Al powder, indicating that the Ba₃V₄O₁₃-BaV₂O₆ ceramics are a candidate material for ULTCC (Ultra-Low Temperature Co-fired Ceramics) applications.

IEEE Standard on Piezoelectricity has been utilized for decades though it has shown significant issues that prevent researchers from obtaining accurate materials coefficients. To resolve these issues, our research group recently proposed partial electrode (PE) method. PE method utilizes samples that consist of the center part covered with electrode, and the side part either covered or not covered with electrode for obtaining both intensive and extensive elastic parameters. In this review, we introduce our PE method, along with physical phenomenology and background, such as issues of IEEE standard, to bolster readers understanding of needs for developing new measurement method that can compensate the standard method. It is shown that development of the PE method not only provides technological benefits, but also gives scientific importance for the piezoelectric research community from its extremely high data accuracy.

The phase evolution, microstructure, and microwave dielectric properties of Ba(Mg_0.5-2xY_2xW_0.5-xTi_x)O₃ (x＝ 0.005~0.05) ceramics sintered at 1,700℃ for 1h were investigated. All compositions exhibited a 1:1 ordered cubic perovskite structure. The field emission scanning electron microscopy image revealed a dense microstructure in all the compositions. As the value of x increased, the lattice parameter, dielectric constant, and quality factor increased. The temperature coefficient of resonant frequency changed from -19.6 ppm/℃ to -5.9 ppm/℃ with increasing x value. The dielectric constant, quality factor, and temperature coefficient of resonant frequency of Ba(Mg_0.40Y_0.10W_0.45Ti_0.05)O₃ were 21.7, 132,685 GHz, and -5.9 ppm/℃, respectively.

Sintering, microstructure, thermal conductivity and microwave dielectric properties of xLiF-(1-x)MgO ceramics (x=0.03-0.10 mol) were investigated. The high density was obtained in the specimens of x≥0.06, i.e., 0.04 LiF-0.96 MgO in mol, whereas the amount of 0.03 mol LiF was insufficient to densify. From the result that the contact flattening in the sintered specimen was observed, the densification occurred through the liquid-phase sintering. The specimen of x=0.06 showed the highest room-temperature thermal conductivity. Relative density, thermal conductivity, dielectric constant, and quality factor (Q x f) of the specimen for x=0.06 sintered at 900°C for 4 h were 97.8%, 39.2 Wm-1K-1, 9.45, and 14,671 GHz, respectively.

Sintering and microwave dielectric properties of Zn2-2xSil+xO4 (x=O-0.10) ceramics were investigated. The secondary phase of ZnO was observed in the specimen for x=O whereas SiO2 was detected in that for x=0.05. The composition of Zn2SiO4 might be close to x=0.02, i.e., Zn1.96Si1.02O4; the ratio of Zn/Si is 1.922. The insufficient grain growth was observed in the specimen of x=O. For the specimens of x≥0.05 , the grain growth sufficiently occurred through the liquid phase sintering. The value of quality factor of all specimens was dependent on the x value, i.e., the ratio of Zn/Si, whereas that of dielectric constant was independent. Relative density, dielectric constant, and quality factor (Q×f) of the specimen for x=0.05, i.e., Znl.9Si1.05O4, sintered at 1,400℃ were 96.5%, 6.43, and 115,166 GHz, respectively.

In this paper, the effect of underpass structure on quality factor and breakdown voltage ofoctagonal inductors which were fabricated with 90 nm complementary metal-oxide-semiconductor (CMOS)technology for radio frequency integrated circuit (RFIC) was studied. It was found that quality factor andbreakdown voltage of inductors with more than one metal layer for underpass showed improvedproperties compared to those with one metal layer. However, little change of quality factor andbreakdown voltage was observed between the inductors with two and more than two metal layers forunderpass. Therefore, underpasses with two metal layers are promising for RFIC designs of the octagonalinductors in 90 nm CMOS technology.