STRUCTURE, MICROSTRUCTURE, AND PIEZOELECTRIC PROPERTIES OF KNLNS-BNKZ LEAD-FREE CERAMICS UNDER THE EFFECT OF DIFFERENT SINTERING TEMPERATURES

Samples of 0.96(K0.48Na0.48Li0.04)(Nb0.95Sb0.05)O3-0.04Bi0.5(Na0.82K0.18)0.5ZrO3 piezoelectric ceramic were fabricated with conventional ceramic techniques and sintered at different temperatures. The effect of sintering temperature (TS) on the structure, microstructure, and piezoelectric properties of the ceramics was studied in detail. The experimental results showed that with an increase of the TS temperature, the structure of the ceramics transformed from an orthorhombic-tetragonal mixed phase (O-T) at TS £ 1100 °C into a rhombohedral-tetragonal (R-T) mixed phase with a dense microstructure of uniform grain size at TS = 1110 °C. When TS was further increased (TS ³ 1120 °C), the ceramics showed only a rhombohedral phase (R). The ceramics showed the best electrical properties for TS = 1110 °C at which the rhombohedral and tetragonal (R-T) phases coexist. Specifically, the ceramic density reached its highest value (4.22 g/cm3), the electromechanical coupling coefficients kp and kt were 0.46 and 0.50, respectively, and the piezoelectric coefficient d33 was 245 pC/N.

Dense ceramics with complex shape fabricated by 3D printing: A review

Three-dimensional (3D) printing technology is becoming a promising method for fabricating highly complex ceramics owing to the arbitrary design and the infinite combination of materials. Insufficient density is one of the main problems with 3D printed ceramics, but concentrated descriptions of making dense ceramics are scarce. This review specifically introduces the principles of the four 3D printing technologies and focuses on the parameters of each technology that affect the densification of 3D printed ceramics, such as the performance of raw materials and the interaction between energy and materials. The technical challenges and suggestions about how to achieve higher ceramic density are presented subsequently. The goal of the presented work is to comprehend the roles of critical parameters in the subsequent 3D printing process to prepare dense ceramics that can meet the practical applications.

Preparation and properties of B4C-TiB2 ceramics prepared by spark plasma sintering

By doping titanium hydride (TiH2) into boron carbide (B4C), a series of B4C + x wt% TiH2 (x = 0, 5, 10, 15 and 20) composite ceramics were obtained through spark plasma sintering (SPS). The effects of sintering temperature and the amount of TiH2 additive on the microstructure, mechanical and electrical properties of the sintered B4C-TiB2 composite ceramics were investigated. Powder mixtures of B4C with 0−20 wt% TiH2 were heated from 1400 to 1800 °C for 20 minutes under 50 MPa. The results indicated that higher sintering temperatures contributed to greater ceramic density. With increasing TiH2 content, titanium diboride (TiB2) formed between the TiH2 and B4C matrix. This effectively improved Young’s modulus and fracture toughness of the composite ceramics, significantly improving their electrical properties: the electrical conductivity reached 114.9 S·cm−1 at 1800 °C when x = 20. Optimum mechanical properties were obtained for the B4C ceramics sintered with 20 wt% TiH2, which had a relative density of 99.9 ± 0.1%, Vickers hardness of 31.8 GPa and fracture toughness of 8.5 MPa·m1/2. The results indicated that the doping of fine Ti particles into the B4C matrix increased the conductivity and the fracture toughness of B4C.

Properties of Al2O3-based ceramics with the addition of ultrafine Al2O3 powder synthesized by electrochemical method

The results of studies of the regularity of sintering and properties of corundum-based ceramics with the addition of ultrafine powder (UFP) Al2O3 synthesized by electrochemical method are presented. It is shown that with an increase in the calcination temperature and the concentration of UFP Al2O3, a regular increase in linear shrinkage, microhardness and strength of ceramics is observed (the maximum values at 1550 °С are 27,8 %, 17 GPa and 340 MPa, respectively). The introduction of UFP Al2O3 allows even at a calcining temperature of 1550 °C to achieve an apparent ceramic density of 3,87 g/cm3. Ref. 12. Tab. 3.

Mechanisms of technical ceramic density adjusting

In this paper authors overviewed the most important stages of ceramics production process which give significant influence on final properties of product. Often density and porosity on the all producing stages determines exploitation ceramics properties. A calculation method for fractions ratio selection which provides optimal density is suggested here. Also, density changes during operations of grinding, forming, thermal treatment and sintering a row of specimens are researched and analysed. The data received allow to predict semi products size behaviour while producing and get definite final part with dimension required.

Effect of Low Temperature Sintering on the Porosity and Microstructure of Porous Zeolite Ceramic

Manufacturing a porous ceramic specimen from natural zeolite materials mined in Malang, Indonesia was conducted by using a low temperature sintering. In this study, a porous ceramic property with rectangular shaped and prism shaped fillets at each end were sintered at 800-900°C and finally were investigated. Density and porosity measurements were performed using Archimedes method. The microstructure photos were used to measure the neck diameter and the contact angle between the two grains particles and two-dimensional porosity. The result of the zeolite ceramic measurement shows that the higher the sintering temperature the higher the density value and the smaller the open porosity. While from the microstructure photo it is shown that the neck diameter was larger the contact angle was wider. This phenomenon was happened because of the flux diffusion on the grain boundaries. This diffusion flow condition would influence the specimen surface, volume and grain boundary so that the porous ceramic density increases.

Physical and Electrical Properties of Cullet-Paper Ash-Kaolin Clay Ceramic

A series of (x) paper ash- (80-x) cullet – 20 Kaolin clay where 10 ≤x≤30 weight % has successfully been prepared using solid state reaction method. The ceramic density and hardness has been determined using Archimedes and Vickers hardness method respectively. The dielectric constant and dielectric loss has been determined using impedance analyzer. The obtained density is descending from 2.18 gcm-3 to 1.90 gcm-3 and hardness is increased up to 871.8 Mpa. The decrement of density and hardness as the cullet content increases is due to the non uniform vitreous areas formed in between ceramic particle. The variation of the dielectric constant and dielectric loss tangent are found to decrease with increasing of frequency which suggest the dipolar polarizability properties. It is found that the maximum value of dielectric constant is 3000 and minimum dielectric loss tangent is 0.166.

Effects of the Addition of Ions Barium on the Structural and Electrical Properties of PZT Ceramic

Lead zirconate titanate, with Zr/Ti ratio of 53/47 was prepared by the polymeric precursor method. It was investigated the barium (II) modification at 0.0, 0.2, 0.4 and 0.6 mol% in substitution to the lead (II) cation in A site of perovskite structure. The powder samples were characterized by XRD and the diffraction patterns were used to Rietveld refinement. The percentages of tetragonal and rhombohedral phases and a systematic study of the effect of barium (II) on the morphology and the dielectric properties of PZT were carried out. The results showed that the tetragonal phase is favored and the ceramic density is improved with the barium (II) insertion. The Curie temperature (Tc) is increased besides the slight reduction of dielectric constant (Kc).

Effect of Tb4O7 Doping on Wear Resistance of High-Alumina Ceramic

It was investigated that the effect of wear resistance of high-alumina ceramic with a series of Tb4O7 additives. It showed that wear resistance of ceramic firstly increased and then decreased with increasing of Tb4O7 doped. And we found that microscopic played the vital role to affect wear resistance of alumina ceramic, decreasing grain sizes would improve the wear resistant. Terbium ions dissolved in liquid phases and the second phase of Tb3Al5O12 appeared would improve microscopic of ceramic, taken grain sizes small and made ceramic density. Doped 0.2wt% Tb4O7, alumina ceramic with small grain sizes had better wear resistance than other ceramic.