Cellulose nanofiber (CNF) has attracted significant attention as a next-generation insulating material due to its ecofriendly nature and outstanding functionalities. However, conventional kraft insulation paper suffers from limited dielectric breakdown strength and long-term reliability under high-voltage conditions, highlighting the need for alternative materials. In this study, kraft pulp was combined with five types of CNFs (A, B, C: wood-based / D, E: non-wood-based) to fabricate composite insulation papers, and their electrical and mechanical properties were systematically evaluated. The results showed that CNF incorporation generally enhanced density and tensile strength, while certain types contributed to lowering dielectric constant and improving breakdown strength. Among the wood-based CNFs, type C exhibited the most balanced performance in terms of dielectric stability and mechanical reinforcement. Among the non-wood-based CNFs, type E demonstrated notable improvements in structural compactness and tensile strength, suggesting favorable reliability. Therefore, this study identifies CNF C among wood-based types and CNF E among non-wood-based types as the most promising candidates for insulation performance enhancement, suggesting their applicability as next-generation insulating materials for power equipment and ecofriendly electronic devices.

This study developed a dielectric composition for high-capacitance MLCCs with C0G and U2J temperature compensation characteristics (Class I) under reducing conditions. The potential application of this composition in highpermittivity class I MLCCs was examined. Using (Ba₀.₂₄Ca₀.₁₆Sr₀.₆)(TiₓZr₁₋ₓ)O₃. XRD analysis showed that secondary phases like Sr₂TiO₄ and TiO₂ formed at higher Ti content, affecting the stoichiometric balance. Adjusting the Ti/Zr molar ratio resulted in a dielectric constant of 41.2 ~ 105, a dielectric loss of 0.082 ~ 0.174%, and insulation resistance above 1.6 × 10¹³ ohms at 25℃. The TCC shifted from C0G to U2J as the Ti/Zr ratio increased, but the composition enabled the design of high-capacitance and high-voltage MLCCs with favorable dielectric and electrical properties.

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 study, the electrical properties of a C0G (class 1 ceramic) dielectric composition with internal reducibility, specifically (Ba_0.27CaSr)(Zr_0.95Ti_0.05)O₃, were investigated by fixing Ba at the A site and varying the Ca/Sr molar ratio. The potential application of this composition in high-permittivity C0G MLCCs was examined. The powder was calcined at 1,150℃ for 2 hours, as determined by TG-DTA analysis, and the resulting powder was ground to achieve a particle size (D50) of 0.35 to 0.4 μm and a specific surface area (BET) of 4.5 to 5.0 g/m². With a Ca/Sr molar ratio of 0.3, the composition (Ba0.27Ca0.17Sr0.56) (Zr0.95Ti0.05)O₃ exhibited electrical properties with a permittivity of 41.9, a loss of less than 0.008%, and an insulation resistance exceeding 2.2×10¹³ Ω. The feasibility of using this composition for high-capacitance C0G MLCCs was confirmed.

In this work, the (K_1-xAg_x)(Ta_0.8Nb_0.2)O₃ (x=0.1-0.4) ceramics were fabricated using mixed-oxide method, and their structural and electrical properties were measured. All specimens represented a pseudo cubic structure with the lattice constant of 0.3989 nm. When 0.4 mol of Ag was added, second phases induced from metallic Ag and K₂(Ta,Nb)₆O₁₆ phase were observed. Dielectric constant and dielectric loss of K(Ta_0.8Nb_0.2)O₃ specimen doped with 0.3 mol of Ag were 2,737 and 0.446, respectively. The curie temperature was about -5℃, which does not change with Ag addition. The remanent polarization began to decrease sharply around 12~15℃, and the temperature at which the remanent polarization began to decrease as the applied voltage increased shifted to the high temperature side. The electrocaloric effect (ΔT) and electrocaloric efficiency (ΔT/ΔE) of the (K_0.7Ag_0.3)(Ta_0.8Nb_0.2)O₃ ceramics were 0.01024℃ and 0.01825 KmV^-1, respectively.

Theoretical background for the meaning of various piezoelectric properties can be easily found in a number of textbooks and academic papers. In contrast, how they are actually measured and characterized are rarely described, though this information would be the most important especially to the researchers who just started working on the field. It follows that this report was intended to provide a practical guidance for measuring basic but essential properties of ferroelectric-based piezoelectric materials. The discussion begins with how to measurement dielectric properties such as dielectric permittivity and loss (dissipation factor), followed by piezoelectric properties such as piezoelectric constants, electromechanical coupling factor, and quality factor as well as ferroelectric features, i.e., electric field dependent polarization hysteresis. Though our discussion here is limited to the techniques that are already well-standardized, it is expected to make a seed to be developed into more challenging and creative ones.

Phase evolution, thermal and microwave dielectric properties of cordierite-Al₂O₃ composite were investigated. As the content of Al₂O₃ increased, mullite, sapphirine, and spinel were formed as secondary phases, implying that cordierite may be decomposed by the reaction with Al₂O₃. All sintered specimens exhibited dense microstructures. The densification occurred through liquid phase sintering. As the content of Al₂O₃ increased, the thermal expansion coefficient and the dielectric constant increased, whereas the quality factor decreased. The thermal expansion coefficient, the dielectric constant, and the quality factor of the 90 wt% cordierite 10 wt% Al₂O₃ composite sintered at 1,425℃ were 2.9×10^-6 K^-1, 5.1, and 34,844 GHz, respectively.

Four types of BaTiO₃ powders are prepared and successfully deposited on glass and Pt/Si substrates using the aerosol deposition process. Particles with sizes of 0.45 μm and 0.3 μm are selected as the starting powder, while those powders are treated using a different milling method. The jet-milled and ball-milled powders not only showed a smaller particle-size distribution, but compared with the non-milled powder, it also had a higher deposition rate using the uniformly generated aerosol. Although the films deposited using particles with size 0.45 μm exhibited some craters on the surface, significantly flat film surfaces were obtained. However, particles with size 0.3 μm create a slightly rough film surface, but the dielectric constant was greater than in the case involving particles with size 0.45 μm. Consequently, a suitably large particle size significantly influences the deposition rate and improvement in the surface roughness, and a uniform particle size distribution appears to contribute to an improved dielectric constant. Therefore, it is believed that the dielectric properties along with the growth characteristics can be enhanced by limiting particle size and shape.

In this study, double layer KTN/STO thin films were fabricated on Pt/Ti/SiO₂/Si substrate, their structural and electrical properties were measured according with the number of STO coatings, and their applicability to microwave materials was investigated. The average grain size was about 80~90 nm, the average thickness of the 6-coated KTN thin film was about 320 nm, and the average thickness of the STO thin film coated once was about 45~50 nm. The dielectric constant decreased with increasing frequency, and as the number of STO coatings increased, the rate of change of the dielectric constant with the applied electric field decreased. The tunability of the KTN thin film showed a maximum value of 19.8% at 3 V. The figure of merit of the KTN/1STO thin film was 9.8 at 3 V.

In this paper, Pb(Mn_1/3Nb_2/3)_0.07(Ni_1/3Nb_2/3)_0.10(Zr_0.5Ti_0.5)_0.83O₃ ceramics were fabricated by the conventional solid state method to obtain excellent dielectric properties for ultrasonic generators. The effects of 2nd calcination temperature on their microstructure and piezoelectric properties were systematically investigated. The tetragonality increased in the ceramics when 2nd calcination temperature increased to the optimized temperature at 750℃. At that temperature, excellent physical properties (d₃₃= 352 pC/N, ε_r= 1,687, k_p= 0.570, Q_m= 1,640) were obtained for ultrasonic generator application.

With trend of the miniaturization and the high-functionalizing of mobile communication system, low-loss microwave dielectric materials are widely used for high frequency communication components. These dielectric materials should be co-sintered with highly electric-conducting metal such as silver or copper for high-frequency and thick film process application. Sintering temperature of Ca[(Li_1/3Nb_2/3)_1-xTi_x]O_3-δ, which has excellent dielectric properties such as ε_r above 40, quality factor (Q·f₀) above 16,000 GHz, and TCF (temperature coefficient of resonant frequency) of -20~-10 ppm/℃, is reported as high as 1,175℃, so it could not be co-sintered with silver or copper. Therefore in this study, low-temperature melting glasses of Zn-B-O and Zn-B-Si-O systems were added to Ca[(Li_1/3Nb_2/3)_1-xTi_x]O_3-δ to lower its sintering temperature under 900℃ without losing excellency of dielectric properties. With 15 weight % of Zn-B-Si-O glass and sintered at 875℃, specimen showed density of 4.11 g/cm³,ε _r of 40.1, Q·f₀ of 4,869 GHz, and TCF of -5.9 ppm/℃. With 15 weight % of Zn-B-O glass and sintered at 87 5℃, specimen showed density of 4.14 g/cm³, ε_r of 40.4, Q·f₀ of 7,059 GHz, and TCF of -0.92 ppm/℃.

The aim of this study is to improve of dielectric properties using epoxy/nano alumina composites with adding glycerol diglycidyl ether (GDE:1,2 g). This paper deals with the effects of dielectric properties(□´ and tan δ) for epoxy/nano alumina contents (1,3 phr) and GDE addition (1,2 g)composites. 5 kinds specimen were prepared with containing epoxy resins, epoxy nano alumina composites. Average particle size of nano used were 30 nm. The nano alumina used were gamma phase particles of spherical shape. The suppression of epoxy chain motion by addition of nano alumina+GDE decreased dielectric loss and relative permittivity magnitude.

In this work, the complex permittivity of epoxy resins is measured. Epoxy resins, epoxy with micro size fillers and epoxy with micro+nano alumina composites have been evaluated for dielectric properties according to frequency variation. The dielectric spectroscopy measurement and analyses are carried out in the frequency range of 10^-2 Hz to 1MHz and constant to room temperature. The results of dielectric loss suggest that significant improvement in the electrical performance can be expected by using samples containing nano and micro fillers mixture when compared to materials containing only microfillers. As the result, we verified the specific characteristics of dielectric permittivity and dielectric loss namely, relative permittivity become low with improving dispersibility of nano+micro mixture composites and become rise with agglomerate of nano particles.

In this study, to develop low temperature sintering capacitor composition ceramics with the good dielectric properties, (Ba0.86Ca0.14)(Ti0.85Zr0.12Sn0.03)O3 (BCTZ) ceramics were prepared by the conventional solid-state reaction method. The effects of B2O3 addition on the dielectric properties and microstructure was investigated. The XRD patterns demonstrated that all the specimens showed Perovskite phase, and secondary phases are indicated in the measurement range of XRD. And also, temperature coefficient of capacitance(TCC) of all the specimen sintered at 1,180℃ showed +3∼-56% except for x=0.006. For all the specimens, observed one peak was tetragonal cubic difuse phase transition temperature(Tc), which is located in the vicinity of room temperature.

In this paper, in order to develop the composition ceramics with the outstanding piezoelectric properties, (Mg_{1/2} W _{1/2} )_{0.03} (OWNS_{1/3} Nb_{2/3})_{0.09} (Zr_{0.5} Ti_{0.5})_{0.88} O_{3} ceramics substituted with BiFeO_{3} were prepared by the conventional solid-state reaction method. The addition of small amount of Li2CO_{3} and CaCO_{3} as sintering aids decreased the sintering temperature of the ceramics. The effects of BiFeO3 substitution on their piezoelectric and dielectric properties were investigated. when 0.015 mol BiFeO_{3} was substituted, the optimal physical properties of d33=590 pC/N, Ec=8.78 kV/mm were obtained.

In this study, in order to develop the capacitor composition ceramics with the good dielectric properties, (Ba0.86Ca0.14)(Ti0.85Zr0.12Sn0.03)O3+ xCuO (x= 0.006~0.010) ceramics were prepared by the conventional solid-state reaction method. The effects of CuO addition on the microstructure and dielectric properties was investigated. All specimens indicated rhombohedra1 phase without any secondary phase. As CuO addition increased, the variation width of TCC was increased at more than 40°C. Also, the specimen with x=0.007 sintered at 1,250°C showed the high dielectric constant of 9,632 in spite of low temperature sintering temperature.

In this paper, in order to develop the composition ceramics with the excellent dielectric properties, Pb(Mg1/2W1/2)0.03(Ni1/3Nb2/3)0.09(Zr0.5Ti0.5)0.88O3 ceramics were fabricated by the conventional solid-state method. The effects of ZnO addition on their microstructure and piezoelectric properties were systematically investigated. The rhombohedral-tetragonal phase coexistence has been found in the ceramics without ZnO content and then with further increasing ZnO content, specimens exhibited tetragonal phase. The optimized ZnO content formed liquid phase and aided the grain growth of specimens. When 0.4 wt% ZnO was added, the optimal physical properties (d33= 422pC/N, d31= 161 pC/N, εr= 1,905, kp= 0.55, Qm= 160) were obtained.

In this study, in order to develop the capacitor composition ceramics with the good dielectric properties, (Ba1-xCax)(Ti0.85Zr0.12Sn0.03)O3 (abbreviated as BCTZ) ceramics were prepared by the conventional solid-state reaction method. The effects of Ca substitution on the microstructure and dielectric properties was investigated. The X-ray diffraction patterns demonstrated that all the specimens showed perovskitephase, and secondary phases are indicated in the measurement range of X-ray diffraction. Also, all the specimens indicated an rhombohedron phase structure. It was identified from the X-ray diffraction patterns that the secondary phase formed in grain boundaries and then decreased the dielectric properties. For all the specimens, observed one peak was tetragonal cubic phase transition temperature(TC),which is located in the vicinity of room temperature.

In this study, (Na0.525K0.443Li0.037)(Nb0.883Sb0.08Ta0.037)O3 + 0.10 wt%Bi2O3 + 0.35 wt%B2O3 ceramics were prepared by conventional soild-state sintering process. The specimens were sintered at temperature range from 1,060℃ to 1,100℃. XRD (X-ray diffractron), SEM (scanning electron microscope) were used to analyze the crystal structure and microstructural sproperties of specimens. And also, TO-T, TC were observed by the mesurement of temperature dependence of dielectric constant. Excellect physical properties of the piezoelectric constant d33= 170 pC/N, electromechanical coupling factor kp= 0.312, Tc= 315℃ were obtained, respectively, from the specimen sintered at 1,080℃.

This research measured the dielectric properties of silicone rubber with various hardness in 100 Hz∼3 MHz, 30∼170℃ conditions. When the hardness increases from 65 degree to 75 degree, the dielectric loss increased within frequency range of 100 kHz～3 MHz and was a little change in dielectric loss within temperature range of 90℃～170℃. Thermogravimetric Analysis (TGA) showed the weight change rate increased a little while heated until 800℃. Scanning Electron Microscope (SEM) measurement showed that Aluminium Trihydroxide(AlOH3) which acts as a reinforcement agent reduced the size of the particles as the hardness increased.

Lead-free piezoelectric ceramic/epoxy composites with ``0-3`` connectivity were prepared by cold-pressing with a temperature controlled curing method. A ceramic powder with a composition of (Na0.51K0.47Li0.02)(Nb0.8Ta0.2)O3 was synthesized by a conventional solid state reaction route. The dielectric and piezoelectric properties of ceramic/epoxy composites were characterized as a function of the volume fraction (φ) of piezoelectric ceramics, which was varied from 70 to 95vol%. The results indicated that the piezoelectric properties of composites were significantly affected by the volume fraction of ceramics. In terms of the piezoelectric properties, specimens showed the best performance at φ= 85vol%, resulting in the piezoelectric constant d33 of 39pC/N and the figure of merit as a piezoelectric energy harvester (d33·g33) of 1.24 pm2/N.

Additions (ZnO, CuO) doped 0.98(Na0.5K0.5)NbO3-0.02Li(Sb0.17Ta0.83)O3 (0.98NKN-0.02LST-x) lead free piezoelectric ceramics have been fabricated by ordinary sintering technique. The effects of additions doping on the dielectric, piezoelectric, and ferroelectric properties of the ceramics were mainly investigated. X-ray diffraction of the sample appeared orthorhombic phase. The specimen doped with additions exhibits enhanced electrical properties (d33= 153 pC/N). These results indicate that the 0.98NKN-0.02LST-x ceramics is a promising candidate for lead-free piezoelectric ceramics for applications such as piezoelectric actuators, harmonic oscillator and so on.

We studied sintering temperature to enhance the piezoelectric properties of 0.98(Na0.5K0.5)NbO3-0.02Li(Sb0.17Ta0.83)O3+0.01wt%ZnO (hereafter NKN-LST+ZnO) lead free piezoelectric ceramics. The synthesis and sintering method were the conventional solid state reaction method and sintering was executed at 1,080∼1,120℃. We found that NKN-LST+ZnO ceramics at optimal sintering temperature showed the improved piezoelectric properties at the optimal sintering temperature. The NKN-LST+ZnO ceramics show good performance with piezoelectric constant d33= 153 pC/N sintered at 1,090℃. The results reveal that NKN-LST+ZnO ceramics are promising candidate materials for lead-free piezoelectric application.

Abstract: The 0.98 (Na0.44K0.52)Nb0.84O3-0.02Li0.04 (Sb0.06Ta0.1)O3-0.5 mol%CuO ceramics have been fabircated by ordinary sintering technique and the effect of various calcination method on the electrical propertis and microstructure have been studied. It was observed that the various calcination method influenced the elelctrical properties and structural properties of the 0.98NKN-0.02LST-0.5 mol%CuO ceramics with the optimum piezoelectric constant (d33) and electromechanical coupling factor (kp) at room temperature of about 155ρC/N and 0.349, respectively, from 0.98NKN-0.02LST-0.5 mol%CuO ceramics sample. The curie temperature (Tc) of this ceramic was found at 440℃. The 0.98NKN-0.02LST-0.5 mol%CuO ceramics are a promising lead-free piezoelectric ceramics.

In this study, piezoelectric and dielectric properties of the (Na0.5K0.5)NbO3-(1-x)(Bi0.5Na0.5)TiO3- xBaTiO3 [NKN-(1-x)BNT-xBT] ceramics were investigated. The lead-free NKN-(1-x)BNT-xBT ceramics were fabricated by a conventional mixed oxide method. The results indicate that the addition of BaTiO3 significantly influences the sintering, microstructure, phase transition and electrical properties of NKN-BNT ceramics. A gradual change in the piezoelectric and dielectric properties was observed with the increase of BT contents. The dielectric constant, piezoelectric constant (d33) and electromechanical coupling factor (kp) increased at the morphotropic phase boundary (MPB). The d33=184 pC/N, kp=0.38, dielectric constant=1455 with dielectric loss value of less than 1% were obtained for the NKN-0.95BNT-0.05BT ceramics sintered at 1150℃ for 2h. These results demonstrate that the NKN-(1-x)BNT-xBT ceramics is an attractive candidate for lead-free piezoelectric materials.