Large Thermal Expansion LTCC System for Cofiring with Integrated Functional Ceramics Layers

We have studied the sintering behavior of CT708 LTCC tapes with large CTE of 10.6 ppm/K. This low-k dielectric LTCC material is a quartz-based glass ceramic composite system with partial crystallization of celsian upon firing. The shrinkage, densification and dielectric properties were examined using different heating rates and a sintering temperature of 900 °C. The maximum shrinkage rate is at 836 °C (for a heating rate of 2 K/min) with a sintering density of 95% and a permittivity of ε’ = 5.9 and tan δ = 0.0004 (at 1 GHz). Due to their similar shrinkage and thermal expansion properties, CT708 tapes may be cofired with functional ceramic layers. As an example, we report on cofiring of a multilayer laminate of CT708 and a Sc-substituted hexagonal ferrite for applications as integrated microwave circulator components. This demonstrates the feasibility of cofiring of functional ceramic tapes and tailored LTCC tapes and documents the potential for the realization of complex LTCC multilayer architectures.

Ceramics of Halychyna in the late 19th – early 20th centuries. Scientific and professional schools. Technologies. Personalities.

An analysis of numerous artefacts of the first third of the 20th century suggests that the production of many varieties of art-and-industrial ceramics developed in Halychyna, in particular architectural ceramic plastics, a variety of functional ceramics, decorative tiles, ceramic tiles, facing tiles, etc. The artistic features of Halychyna art ceramics, the richness of methods for decorating and shaping it, stylistic features, as well as numerous art societies, scientific and professional associations, groups, plants and factories specializing in the production of ceramics reflect the general development of this industry in the first half of the century and represent the prerequisites the emergence of the school of professional ceramics in Halychyna at the beginning of the 20th century. The purpose of the paper is to analyze the formation and development of scientific and professional schools of art-and-industrial ceramics of Halychyna in the late 19th – early 20th centuries. The research methodology was chosen, in accordance with the specific factual material, the goals and objectives set in the work, developed on the basis of a systematic approach and the principle of historicism, using the method of complex art analysis, synthesizing the research capabilities of comparative historical, functional, typological research methods. The principle of consistency assumed the consideration of certain issues, in accordance with the sequence of processes that took place in such a popular variety of professional decorative applied art as art ceramics. Due to this approach, the authors tried to focus on a detailed elucidation of the ways of building professional creativity in an inextricable relationship, taking into account the characteristics of a certain material, the needs of appropriate material support, and the establishment of technological processes. Furthermore, such a presentation of the paper material has provided a clearer indication of the possibilities and prospects for the development of the artistic ceramics art. In the process of work, the authors were aware that all the problems related to the art of the first half of the 20th century, including the development in the production of art ceramics in Halychyna, are only at a certain stage of thorough study. That is why this work is one of the stages on this path. In this regard, this study was interpreted by the authors not as one that should finally exhaust the chosen topic, but on the contrary – the work should create an opportunity for further more detailed study of individual phenomena, the work of artists, or the analysis of groups of specific pieces of art.

Relationship of Electrical Properties and Partical Size of Piezoelectric Ceramics Fabricated by Digital Light Processing 3D Printing

To improve electrical properties of BaTiO3 piezoelectric ceramics fabricated by 3D printing, effects of particle sizes was investigated on rheological and curing properties of ceramic slurries, electrical properties of BaTiO3 fabricated by Digital Light Processing 3D printing method. It was found that the curing ability of ceramic slurries decreased first and then increased with the increase of particle size from 136 nm to 1486 nm, while the viscosity of the slurries kept decreasing. When the particle size in a range of submicron, the grain size of sintered ceramics decreased from 13.27 μm to 6.84 μm as particle size increasing. Immediately, the relative density, piezoelectric constant, relative permittivity and remanent polarization of sintered ceramics were measured and it turns out to reach 95.32%, 161.4 pC/N, 1512 and 7.59 uC/cm2 respectively while using the BaTiO3 powder with particle sizes of 993 nm. Finally, a cellular structural BaTiO3 ceramics was fabricated by using optimized powder and process parameters and packaged as a piezoelectric sensor, showing a good function of force-electricity conversion. These results demonstrated the feasibility of fabricating high-quality functional ceramics with designed geometry by Digital Light Processing.

Structure and Properties of Barium Titanate Lead-Free Piezoceramic Manufactured by Binder Jetting Process

This article presents the results of manufacturing samples from barium titanate (BaTiO3) lead-free piezoceramics by using the binder jetting additive manufacturing process. An investigation of the manufacturing process steps for two initial powders with different particle size distributions was carried. The influence of the sintering and the particle size distribution of the starting materials on grain size and functional properties was evaluated. Samples from fine unimodal powder compared to coarse multimodal one have 3–4% higher relative density values, as well as a piezoelectric coefficient of 1.55 times higher values (d33 = 183 pC/N and 118 pC/N correspondingly). The influence of binder saturation on sintering modes was demonstrated. Binder jetting with 100% saturation for both powders enables printing samples without delamination and cracking. Sintering at 1400 °C with a dwell time of 6 h forms the highest density samples. The microstructure of sintered samples was characterized with scanning electron microscopy. The possibility of manufacturing parts from functional ceramics using additive manufacturing was demonstrated.

Overview of Spark Plasma Texturing of Functional Ceramics

This work reports the progress in the preparation of superconducting and thermoelectric lamellar compounds processed by the unconventional Spark Plasma Sintering (SPS). The SPS equipment was modified with the aim of obtaining the textured and dense superconductor Bi2Sr2Ca2Cu3O10,p-type oxide thermoelectric bulk as Ca3Co4O9 and Ca3-xAgxCo4O9/Ag composites respectively. The new process is referred to as Spark Plasma Texturing (SPT). During SPT, the bulk material can freely deform. As a result, inter-grain preferential crystallographic orientation is created. The series of sintered and textured samples using the same Ag content were processed respectively. From the results, we can evidence: (i) the magnetic and/or structural transition around 350 °C, for both series of samples. (ii) The electrical resistivity (ρ) decreases with increasing Ag-substituted or Ag-added. (iii) The Seebeck coefficient (S) of the textured series is higher than that of the sintered series. In the case of the Ag-substituted, S, decreases with Ag content. The optimized composite is found to be Ca2.6Ag0.4Co4O9/8wt% Ag. We can note the remarkable reduction of ρ, and the improvement of power factor values up to 360 μW.m−1.K−2.The superconducting properties of single phased Bi2Sr2Ca2Cu3O10 (Bi2223) consolidated using SPS and SPT will also be discussed.