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SiO2‐Al2O3‐CaO‐based glass (10–60 wt%)/mullite composites were investigated for the LTCC and radome applications. The optimum densification temperatures decreased from 1550°C (10 wt% glass) to 1400°C (30 wt% glass) by means of liquid‐phase sintering, and to 850°C–825°C (50–60 wt% glass) by means of viscous phase sintering. XRD analysis showed that mullite was the main phase as well as in situ crystallized anorthite after 825°C. The composite with 20 wt% glass was a suitable candidate for the radome applications (bulk density = 2.86 g/cm3 after sintering at 1450°C, dielectric constant (loss) = 7.12 (0.0025) at 5 MHz, thermal expansion coefficient = 4.27 ppm/°C between 25°C and 800°C, thermal shock resistance parameter = 162°C), and the composite with 50 wt% glass was a suitable candidate for the low‐temperature cofired ceramic applications (bulk density = 2.64 g/cm3 after sintering at 850°C, dielectric constant (loss) = 6.79 (0.0043) at 5 MHz, thermal conductivity = 2.11 W/m⋅K at 25°C, and thermal expansion coefficient = 3.93 ppm/°C between 25°C and 300°C). [ABSTRACT FROM AUTHOR]

Mullite/glass/nano aluminum nitride (AlN) filler (1–10 wt% AlN) composites were successfully fabricated for the low‐temperature co‐fired ceramics applications that require densification temperatures lower than 950°C, high thermal conductivity to dissipate heat and thermal expansion coefficient matched to Si for reliability, and low dielectric constant for high signal transmission speed. Densification temperatures were ≤825°C for all composites due to the viscous sintering of the glass matrix. X‐ray diffraction proved that AlN neither chemically reacted with other phases nor decomposed with temperature. The number of closed pores increased with the AlN content, which limited the property improvement expected. A dense mullite/glass/AlN (10 wt%) composite had a thermal expansion coefficient of 4.44 ppm/°C between 25 and 300°C, thermal conductivity of 1.76 W/m.K at 25°C, dielectric constant (loss) of 6.42 (0.0017) at 5 MHz, flexural strength of 88 MPa and elastic modulus of 82 GPa, that are comparable to the commercial low temperature co‐fired ceramics products. [ABSTRACT FROM AUTHOR]

2.5Bi(Zn0.5Zr0.5)O3−37.5BiScO3−60PbTiO3 (BZZ-BS-PT) ceramics were successfully textured in the [001] by templated grain growth (TGG) process using 5 vol% <001>-oriented BaTiO3 (BT) plate-like templates. The templates were aligned in the matrix powder via tape casting and textured BZZ-BS-PT ceramics sintered at 1100°C for 3 h in air had a relative density of 98% and a Lotgering factor of 0.91. Chemically stable BT templates in Pb and Bi-rich BZZ-BS-PT system gave rise to the formation of highly oriented polycrystalline structure with larger block-like grains. A very high unipolar strain of 0.3% and low-field (<5 kV/cm) piezoelectric charge coefficient (d33) of 930 pm/V when driven at 50 kV/cm were achieved in highly textured ceramics together with a Curie temperature (TC) of 403°C. The TGG approach significantly improved piezoelectric properties of the BZ-BS-PT ceramic system without deteriorating the dielectric properties, which is a very promising high-performance candidate for high-temperature sensor, transducer and actuator applications. [ABSTRACT FROM AUTHOR]

Al2O3/glass/hBN composites were successfully fabricated for the LTCC applications. Alignment and homogeneous distribution of the platelet hBN particles during tape casting allowed high hBN (5 wt%) loading as well as facilitated densification at 800°C (density of 2.65 g/cm3, apparent porosity of 0.7%). XRD results proved that hBN neither chemically reacted with the other phases nor decomposed with temperature, which was critical to increase thermal conductivity and at the same time to decrease dielectric constant. Dielectric constant of the dense composites decreased (or, alternatively, enhanced) with increasing hBN content from 7.3 for the 0 wt% hBN to 6.55 for the 5 wt% hBN at 5 MHz. In addition, hBN addition strongly improved the mean thermal conductivity from 1.86 W/m·K for the 0 wt% hBN to 2.43 W/m·K for the 5 wt% hBN between 75°C and 250°C. Therefore, the hBN phase itself effectively optimized both dielectric and thermal properties at the same time and made the Al2O3/glass/hBN composites a promising candidate for the LTCC applications. [ABSTRACT FROM AUTHOR]

Gel‐casting method was used to fabricate mullite ceramics because this method has not been applied to fabricate dense mullite in literature. Gel‐casting parameters such as monomer types (acrylamide and metyhlenebisacrylamide), effect of initiator (ammonium persulfate), and catalyst (tetramethylenediamine) were studied. All samples reached to relative densities of 97% to 98.2% after sintering at 1540°C for 2 hours. Backscattered SEM images revealed anisotropically grown mullite grains, glassy phase located at triple junctions, hexagonally‐shaped and faceted Al2O3 grains, and white‐color grains consisting of ZrO2 and undissolved TiO2. A Weibull modulus of 12.33 (ie, indicating tough ceramics) and characteristic strength of 186 MPa were calculated, below which no failure was expected. A critical quenching temperature was found as about 400°C (ΔT ~ 380°C) by indentation‐quench method. In addition, a thermal shock resistance parameter (eg, R in °C) of 142.4°C was calculated, which was higher than commonly used Al2O3 ceramics. Lower dielectric constant and loss are desired for wide frequency band application and shorter signal transmission delay time in radomes. The dielectric constant was found as nearly 7.5 up to 10 GHz and loss tangent was 0.0031 at 5 MHz. Dielectric and thermomechanical results suggest that mullite is a suitable candidate ceramic for radome applications. [ABSTRACT FROM AUTHOR]

〈001〉-textured Pb(Mg1/3Nb2/3)O3-Pb(Yb1/2Nb1/2)O3-PbTiO3 ceramics were successfully textured in [001] via the template grain growth method using 1-7 vol% platelike BaTiO3 (BT) templated (the Lotgering factor of 0.91 at 5 vol% BT). Dielectric spectra indicated a normal ferroelectric behavior without any frequency dispersion and no low-temperature phase transition. The chemically stable BT phase within the matrix gave rise to a composite effect and its relatively inferior properties affected the dielectric and electromechanical properties. The lower TC of the BT decreased the Curie temperature from 226 to 213 °C (with a depolarization temperature of 204 °C). Significantly higher levels of strain (0.33%), narrower hysteresis level (7.7%), higher piezoelectric strain coefficient (660 pm/V), and low-field (,5 kV/cm) piezoelectric strain coefficient (1340 pm/V) at 50 kV/cm were achieved at 5 vol% BT addition. These results are very promising for the fabrication of high performance transducer and actuator applications without severe temperature limitations. [ABSTRACT FROM AUTHOR]

0.62[0.75(Pb(Mg 1/3 Nb 2/3 )O 3 )–0.25(Pb(Yb 1/2 Nb 1/2 )O 3 )]–0.38(PbTiO 3 ) ceramics were successfully textured in [001] (Lotgering factor of 0.91) using plate-like BaTiO 3 templates, for the first time. Samples were densified to 98% of the theoretical density. Significantly higher levels of strain (0.33%) and low-field (< 5 kV/cm) d 33 coefficient (1340 pm/V) together with a narrower hysteresis level (7.7%) at 50 kV/cm have been achieved in the textured ceramics. These results are very promising for high performance transducer and actuator applications without severe temperature restriction due to their higher T c values (214 °C) and also open up new opportunities for the concept of domain engineering in the textured ceramics. [ABSTRACT FROM AUTHOR]