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(1 − x)CaTiO3–xLa(Mg2/3Nb1/3)O3 (CT–LMN; x = 0–1.0) solid solutions were prepared by a solid‐state reaction method. A phase transition from a disordered orthorhombic (Pbnm) structure to a 1:1 ordered monoclinic (P21/n) structure was observed when x increased from 0.5 to 0.6. Some new parameters, such as ionic polarizability in a polyhedron and ionic packing fraction in a polyhedron, were defined to explain the structure–property relationships of CT–LMN ceramics based on the Rietveld refinement results. The measured dielectric constant (εr‐mea) decreased monotonically with B‐site ionic polarizability in the [BO6] octahedron (αDT(B)/V[B]$\alpha _{\rm{D}}^{\rm{T}}({\rm{B}})/{V_{[ {\rm{B}} ]}}$) when the x value increased from 0 to 1.0. The quality factor (Qf) was dominated by the packing fraction of B‐site cations in the [BO6] octahedron (PF[B]), and both presented an increasing trend. The temperature coefficient of resonant frequency (τf) decreased from +588.5 to −79.7 ppm/°C, and it was highly correlated to the tolerance factor (t), αDT(B)/αDT(B)V[B]V[B]${{\alpha _D^T({\rm{B}})} \mathord{/ {\vphantom {{\alpha _D^T({\rm{B}})} {{V_{[ {\rm{B}} ]}}}}} \kern-\nulldelimiterspace} {{V_{[ {\rm{B}} ]}}}}$ and PF[B]. The highest Qf value is obtained at x = 1.0 when sintered at 1600°C for 10 h with εr = 23.65 ± 0.2, Qf = 33517 ± 2000 GHz (@7.8 GHz), and τf = −79.7 ± 2.0 ppm/°C. Moreover, a near‐zero τf value was achieved at x = 0.4 with εr = 43.52 ± 0.2, Qf = 17239 ± 2000 GHz (@5.2 GHz), and τf = −10.2 ± 2.0 ppm/°C. [ABSTRACT FROM AUTHOR]

ZTM ceramics comprising of 0.75ZnAl2O4–0.25TiO2 and MgTiO3 at a ratio of 90:10 wt.% are widely used in the field of communication as filters and resonators owing to their excellent microwave dielectric properties. However, the development of such dielectrics with complex structures, as required by microwave devices, is difficult using traditional fabrication methods. In this study, ZTM microwave dielectric ceramics were prepared using the digital light processing (DLP) technology. The influence of the sintering temperature on the phase composition, microstructure, and microwave dielectric properties of ZTM ceramics was investigated. Results showed that with an increase in the sintering temperature, the dielectric constant (εr) and quality factor (Q × f) of ZTM ceramics initially increased owing to the increase in the density and diffusion of ions. However, when the sintering temperature was excessively high, the abnormal growth of crystal grains and micropores led to a decrease in εr and Q × f. The ZTM ceramics sintered at 1450°C exhibited the optimum microwave dielectric properties (εr = 12.99, Q × f = 69 245 GHz, τf = −9.50 ppm/°C) owing to the uniform microstructure and a high relative density of 95.02%. These results indicate that DLP is a promising method for preparing high‐performance microwave dielectric ceramics with complex structures. [ABSTRACT FROM AUTHOR]

A novel and rapid fabrication method for Al2O3 ceramics by the DCC‐HVCI method via microwave heating was proposed. Effects of microwave heating temperature on coagulation time, micromorphology, as well as performance of the green body and ceramic sample were studied. As the microwave heating temperature rises, the coagulation time gradually reduced and compressive strength of green sample decreased while relative density and flexural strength of ceramics rose at the beginning and then dropped. The 50 vol.% Al2O3 suspension was coagulated and demolded after treating at 60°C for 800 s by microwave heating. The compressive strength of green samples reached 1.12 ± 0.13 MPa. The relative density of Al2O3 ceramic samples reached 99.39%. And the flexural strength of Al2O3 ceramics reached 334.55 ± 26.41 MPa. The Weibull modulus of Al2O3 ceramics reached 19. In contrast with the ceramic samples heated through water bath, the ceramic samples treated through microwave possessed uniform microstructures. Microwave heating could reduce the coagulation time by 77%. Meanwhile, it could significantly raise the compressive strength of green bodies by 65%. Additionally, it could increase the flexural strength of ceramics by 30%. [ABSTRACT FROM AUTHOR]

Abstract: Flawless porous fibrous alumina ceramics with high performance were fabricated via a novel approach involving direct coagulation casting and lost‐mold method. Stable alumina suspensions were prepared by adding sodium tri‐polyphosphate as dispersant using alumina fibers as raw material and K2SO4 as sintering aid. Resin‐coated sand molds with designed shapes for suspension casting were fabricated through 3D printing with subsequent post‐treatments. Alumina green bodies were obtained by in situ coagulation of the suspension after treating at 90°C within 40 minutes. Porous alumina ceramics were obtained after direct furnace sintering of green bodies without demolding, in which the molds would collapse automatically at around 650°C with less exhaust emission. The effect of various K2SO4 contents and sintering temperatures on mechanical properties of porous ceramics was investigated. The SEM results showed that the fibers interconnected with obvious interfacial bondings on junctions when sintered at 1450°C. The XRD patterns showed that the sample sintered with various K2SO4 additions consisted of different phases, mainly including aluminosilicates. Porosity of ceramic samples increased slightly whereas the compressive strength enhanced significantly with increasing K2SO4 addition. The density of sintered samples with different K2SO4 contents was in accord with the porosity variation tendency. The ceramic samples had uniform pore size distribution with average size from 3.18 to 7.24 μm as increasing K2SO4 addition to 40 wt%. This approach may provide a convenient and general route to fabricate various dense and porous advanced ceramics with complex shapes and good composition homogeneity. [ABSTRACT FROM AUTHOR]

Abstract: A novel method for fabrication of highly porous barium strontium titanate (BST) ceramic foams based on particle‐stabilized foaming method was developed for the first time, in which propyl gallate (PG) was employed as BST particle modifier. The results showed that the stability of wet BST foams closely depends on the pH value and PG concentration, which could be explained by the adsorption behavior of PG on BST particle surface. BST ceramic foams with dense, uniform, and closed pore and defect‐free wall were obtained. The pore size and porosity can be well controlled by adjusting solid loading and sintering temperature. It was revealed that not only sintering temperature but also solid loading significantly influenced the growth of BST grain. The BST ceramic foams exhibited high porosity in the range of 81%‐95%, low dielectric constant in the range of 47‐150, and low dielectric loss below 0.0025. The BST ceramic foams with higher porosity presented a tendency of lower dielectric constant and the fitting results indicated that the natural logarithm of dielectric constant was linear correlated with porosity. [ABSTRACT FROM AUTHOR]

In this paper, a novel fabrication method for glass foams has been introduced based on colloidal suspension foaming method using waste glass as starting materials. It is demonstrated for the first time that foam stabilization via in-situ hydrophobization of waste glass particles is possible. The fabrication conditions for stable glass particle-stabilized foams are optimized by investigating the influences of pH value, concentration of propyl gallate and ball milling time, respectively. It is demonstrated that this is a versatile method for fabrication of stable foamed glass suspension and final glass foams with small pore size of dozens of microns, which is much smaller than that of most glass foams in previous literatures. This novel method enables both closed pore structure and open pore structure simply by tailoring solid loading of glass suspension. A "sieve-like" hierarchical pore structure can be achieved by adjusting sintering temperature. The glass foams with controllable structure could be applied in thermal insulation fields for closed pores, and in catalyst loading, filtration, and separation fields for open pores and hierarchical pore structure. [ABSTRACT FROM AUTHOR]

A novel forming method-aqueous gelcasting was used to assist conventional solid-state method to prepare 45 wt% Ba0.6 Sr0.4 TiO3-55 wt% MgO ( BSTM) ceramic powders. For comparison purpose, conventional solid-state method was also used to synthesize the same powders. It is found that the BSTM ceramic powders prepared by our method are more uniform with smaller and more sphere-like particles than those prepared by the conventional method, whereas the phase compositions are completely the same no matter what powder preparation method is adopted. In addition, the BSTM green samples and ceramics from powders prepared by our method are more uniform than those from powders prepared by the conventional method. Moreover, it is found that using this novel method to prepare BSTM ceramic powders could not only improve the dielectric properties of the BSTM ceramics, but also decrease their sintering temperature. Aqueous gelcasting-assisted solid-state method could be a novel promising method to prepare high performance ceramic powders in the future. [ABSTRACT FROM AUTHOR]