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Purpose Aluminum nitride (AlN) ceramics are suitable substrate and package materials for high-power integrated circuits.Design/methodology/approach Dense AlN ceramics with Y2O3 and LaF3 as sintering additives are prepared. The effects of these additives on the density, phase composition, microstructure and thermal conductivity of AlN ceramics are investigated.Findings Results show that 2 Wt.% Y2O3-doped additive is insufficient for the samples to achieve the full densification sintered at 1,700°C. When LaF3 is added with Y2O3, the samples are perfectly densified at the same sintering condition. The relative density and thermal conductivity of the samples are 97.8-99.07 per cent and 169.104-200.010 W·m-1·K-1, respectively. The density of the samples and their microstructure, especially the content and distribution of secondary phases, is necessary to control the thermal conductivity of AlN ceramics.Originality/value Y2O3 and LaF3 additives can effectively promote densification and enhance the thermal conductivity of AlN ceramics in a low sintering temperature, and the AlN ceramics added with Y2O3-LaF3 might have potential applications in package materials for high-power integrated circuits. [ABSTRACT FROM AUTHOR]

A new organic fuel (poly(acrylic acid)) was adopted to fabricate well-dispersed Y 2 O 3 nano-powders according to the solution combustion method. The improved combustion method requires no tedious operation or restriction conditions. The effects of organic fuel dosage and calcination temperature on the characteristics of Y 2 O 3 powders were investigated. The results indicate that the Y 2 O 3 can be formed at 400 °C and well crystallined at 500 °C with a nitrate and organic fuel mass ratio of 7:1. The addition of organic fuel significantly improves the dispersity and reduces the particle size of Y 2 O 3 powders, whereas the increase in calcination temperature leads to the slight increase in the particle size of the Y 2 O 3 powders. The well-dispersed Y 2 O 3 powders with the particle size range of 10–30 nm are obtained at 500 °C when the mass ratio of the organic fuel and nitrate is 7:2. The poly(acrylic acid) is a new and feasible fuel for the solution combustion method to prepare well-dispersed Y 2 O 3 nano-powders. [ABSTRACT FROM AUTHOR]

Ammonium polyacrylate was adopted for the first time to fabricate nanosized Nd:Y2O3powders with good dispersity through solution-combustion method. Results indicate that cubic Y2O3can be synthesized at a relatively low temperature (300°C) and that the crystallinity of powder increases with increased calcination temperature. TEM observations reveal that the influence of improve with increased organic-fuel dosage. Well-dispersed Nd:Y2O3particles with a narrow size distribution of 20–40 nm can be obtained when the mass ratio of ammonium polyacrylate to yttrium nitrate is 0.5:1. Therefore, ammonium polyacrylate is a new fuel that can be used to prepare well-dispersed Nd:Y2O3nanopowders. [ABSTRACT FROM PUBLISHER]

The aqueous gelcasting-assisted solid-state method (AGAS) and traditional solid-state reaction method (TSSR) were used to prepare Ba[(CoZn)Nb]O (BCZN)-based ceramics. The effects of different powder-preparation methods on the microstructures and dielectric properties of the BCZN-based ceramics were investigated. X-ray diffraction analysis showed completely the same phase compositions regardless of the preparation method adopted. The relative permittivity ( ε) did not significantly vary between the two methods. However, BCZN with CeO-added ceramics prepared by AGAS had higher and more uniform density (6.374 g/cm) and high quality factor of resonant frequency ( Q × f) value (75,843 GHz) than those prepared by TSSR because of the more uniform microstructures, as shown by scanning electron microscopy images. The temperature coefficients of resonant frequency ( τ = 7.4 ppm/°C) of the ceramics prepared by AGAS were also closer to zero than those prepared by TSSR. [ABSTRACT FROM AUTHOR]

Abstract: Approximately 400nm grain sized boron–carbon ceramic was synthesized by the pulsed electric current sintering (PECS) method using boron and carbon powders. Relative density of up to 95% was achieved at sintering temperature of 1900°C. This ceramic was composed with B13C2 as major phase and few B4C and C, which were characterized by X-ray diffraction (XRD) and Rietveld refinement quantitative analysis and chemical analysis (CA) and electron probe microanalysis (EPMA). The microstructure was also observed via transmission electron microscope (TEM). [Copyright &y& Elsevier]

Abstract: The effects of SrTiO3 additives on the microstructure and the dielectric properties of Ba4.2Sm9.2Ti18O54 (BST) materials have been investigated. The microstructure of BST doped with SrTiO3 was analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM) and electron probe microanalyzer (EPMA). The XRD, SEM and EPMA results showed that small amounts of SrTiO3 (less than 4wt.%) could be accommodated in BST while a secondary metatitanate phase appeared in the samples with 8wt.% SrTiO3 added, the addition of SrTiO3 increased the lower solubility limit (x values) of Ba6−3x Sm8+2x Ti18O54. The relative permittivities and the TCf values showed an approximately linear increase with increasing additions of SrTiO3. It was observed that near zero TCf values could be achieved with the addition of SrTiO3 to BST ceramics. With 4wt.% SrTiO3 addition and sintered at 1360°C for 2h, BST ceramics exhibited excellent dielectric properties: ɛ r =81.2, Q f =8470GHz and TCf =−1.5ppm/°C. [Copyright &y& Elsevier]

Abstract: The stoichiometry of B–C thin films was controlled via pulsed laser deposition using a series of ceramic B–C targets (B/C ratio was 3.04–5.92). The effects of B/C ratio in target, laser power and substrate-to-target distance on deposition rate, microstructure, stoichiometry and chemical structure were investigated. The maximum deposition rate was obtained at laser power of 90mJ and substrate-to-target distance of 50mm. Boron rich B–C films were obtained and the stoichiometry in B–C thin films was controlled in the range 2.9–4.6. Carbon atoms were bonded with only sp3 hybridization when boron was rich,but with sp2 and sp3 hybridizations when carbon was rich. [Copyright &y& Elsevier]

Abstract: Li2ZnTi3O8 ceramics doped with ZnO–B2O3 frit were prepared by the conventional solid-state reaction. The effects of the ZnO–B2O3 frit on the sintering characteristic, phase composition, microstructure and microwave dielectric properties of Li2ZnTi3O8 ceramics were investigated. A single-phase Li2ZnTi3O8 is formed and no secondary phase is found in the XRD patterns. It is also found that ZnO–B2O3 frit can lower the sintering temperature of the ceramics by about 200°C without seriously deteriorating the microwave dielectric properties. Typically, the ceramics doped with 0.25wt.% ZnO–B2O3 frit sintered at 950°C show good microwave dielectric properties of εr =25.34, Q×f=61,660GHz, and τf =−12.98ppm/°C. [Copyright &y& Elsevier]

Porous SiC film is an excellent electrode material for robust micro-supercapacitors used in extremely harsh environments. In one of our previous studies, porous 3C–SiC film with high areal capacitance and high deposition rate was prepared via laser chemical vapor deposition (LCVD). However, it is still urgent to explore the formation mechanism of porous structures using LCVD. In this study, the microstructure of the porous cubic SiC film prepared via LCVD was analyzed in detail using scanning and transmission electron microscopy techniques. The growth mechanism of the deposits has been proposed according to the "growth competing theory" and "shadow effect theory." [ABSTRACT FROM AUTHOR]

Y 2 O 3 ceramics with good dielectric properties were prepared via co-precipitation reaction and subsequent sintering in a muffle furnace. The effects of Nd doping and sintering temperature on microwave dielectric properties were studied. With the increase in sintering temperature, the density, quality factor ( Q × f ), and dielectric constant ( ε r ) values of pure Y 2 O 3 ceramics increased to the maximum and then gradually decreased. The Y 2 O 3 ceramics sintered at 1500 °C for 4 h showed optimal dielectric properties: ε r =10.76, Q × f =82, 188 GHz, and τ f =−54.4 ppm/°C. With the addition of Nd dopant, the Q × f values, ε r , and τ f of the Nd: Y 2 O 3 ceramics apparently increased, but excessive amount degraded the quality factor. The Y 2 O 3 ceramics with 2 at% Nd 2 O 3 sintered at 1460 °C displayed good microwave dielectric properties: ε r =10.4, Q × f =94, 149 GHz and τ f =−46.2 ppm/°C. [ABSTRACT FROM AUTHOR]

YAG ceramics with good dielectric properties were prepared via a modified pyrolysis method, with yttrium nitrate as the yttrium source and combined aluminium sulphate and aluminium nitrate as aluminium sources, and subsequent sintering in a muffle furnace. The effects of the different aluminium sources on the powder characteristic and the impact of sintering temperature, sintering aids (TEOS) and additive (TiO 2 ) on the dielectric properties of the ceramics were studied. The results show that well-dispersed pure YAG nano-powders can be obtained after calcination at 1000 °C with an aluminium sulphate and aluminium nitrate molar ratio of 1.5:2. The relative density, permittivity ( ε r ) and quality factor ( Q × f ) of the YAG ceramics increase with sintering temperature and TEOS addition. TiO 2 can greatly promote τ f to near-zero but decreases Q × f . The relative density, ε r , Q × f and τ f of the YAG–1 wt% TEOS–1 wt% TiO 2 ceramic obtained at 1520 °C are 97.6%, 9.9, 71, 738 GHz and −30 ppm/°C, respectively. [ABSTRACT FROM AUTHOR]