Effect of Sintered Magnesium Substituted Biphasic Calcium Phosphate (Mg-BCP)

Biphasic Calcium Phosphate (BCP) is a ceramic material that consisting of two phases which is Hydroxyapatite (HA) and β-Tricalcium Phosphate (β-TCP). In this work, BCP and Mg-BCP (Mg Doped) was synthesized using aqueous precipitation method at standard room temperature and pressure. The synthesized powder was pressed into pellet and sintered at three consecutive temperatures of 800 °C, 900 °C, and 1000 °C. The sintered pellet was characterized using XRD to obtained the quantification analysis on phases presence and to study the crystal orientation of HA and β-TCP before and after Mg doping was introduced. FTIR was used to determine chemical constituents of synthesized powders. Diameter shrinkage analysis was performed to study the effect of temperatures on the densification of the pellet body and SEM was used to observed the morphology of each pellet. Based on the XRD result, the Mg doping is affecting the stability of the phases presence and the crystal lattice creating a distortion due to the substitution of smaller Mg ion. Analysis on the SEM morphology have shown that Mg doped BCP resulting a dense structure with less formation of porosity, necking was formed clearly at temperatures of 900 °C to 1000 °C.

SYNTHESIS AND CHARACTERIZATION OF LEAD-FREE PIEZOELECTRIC (K0.5Na0.5)NbO3 PRODUCED WITH IMPROVED CALCINATION TEMPERATURE

Potassium sodium niobate (KNN) is one of the lead free piezoelectric material that catch the attention of researchers and also those in the industrial field because of its stable piezoelectric responses and environmental friendly composition. The recent development of KNN shows that many methods have been used to synthesize the KNN but the stoichiometric Ka0.5Na0.5NbO3 composition is extremely difficult to consolidate. One of the ways to overcome the problem is to precisely pre-calcine and use milling process for proper homogenization followed by natural sintering process. In this paper, attempt has been made to synthesize the KNN produced at 750 oC calcination temperature. The results of 1060oC sintering temperature for 2 hours show a good composition of KNN with orthorhombic crystal structure where the final sintered pellet can reach to a relative density up to 87.13 %.

Investigation on temperature-dependent electrical properties of La1−xAxCoO3 (A – La, Li, Mg, Ca, Sr, Ba)

Surface of the sintered pellet of LaCoO3 and Cole–Cole plot revealing the contribution from grain and grain boundary on its electrical properties.

Crystal Structure and Electrical Properties of (1-x) (Ba0.85Sr0.15)TiO3 - x(K0.5Na0.5)NbO3 System

The composition of (1-x) (Ba0.85Sr0.15)TiO3 – x (K0.5Na0.5)NbO3 (BST-KNN) for x=0.1 and x=0.2 were successfully prepared by two separate synthesis namely oxalate co-precipitation (for BST) and solid-state reaction (for KNN). Sintered pellet at 1200 °C for 2h exhibits a single phase except x= 0.2 showing a secondary phase and was identified as Ba2TiO4. KNN doped BST system show tetragonal symmetry in which higher dopant expand its tetragonality (c/a). The density of sintered samples deduced by Archimedes method are slightly higher than 90%. Permittivity measurements as function of temperature show almost similar Tc= 90 °C at frequency 1.273 kHz and shift to higher temperature as frequency increases indicating a typical relaxor characteristics. At room temperature the relative permittivity showing Debye relaxation characteristic with ωr=12560 (x=0.1) and ωr =20096 (x-0.2). Furthermore, as function of temperature the activation energy deduced from relaxation time was obtained Ea=0,564 eV for x=0.1 and 0,58 eV for x=0.2.

Electrical Behavior of Electric Field-Assisted Pressureless Sintered Ceria-20 mol% Samaria

CeO2:20 mol% Sm2O3 green ceramic pellets were sintered conventionally at 1500 °C/2 h and flash sintered by applying a 200 V cm−1 electric field at 800 °C, 1000 °C and 1200 °C. The thickness shrinkage of the pellets was followed bythe specimen being positioned inside a dilatometer adapted with platinum electrodes and terminal leads connected to a power supply for application of the electric voltage. The microstructure of the surfaces of the sintered samples were observed in a scanning electron microscope. The electrical properties were evaluated by the impedance spectroscopy technique in the 5 Hz–13 MHz frequency range from 210 °C to 280 °C. The main results show that (i) the final shrinkage level is nearly independent of the temperature when the electric field is applied and slightly better than that of the 1500 °C sintered pellet, and (ii) the bulk conductivity of the sample flash sintered at 1200 °C is similar to that of the sample sintered at 1500 °C. The availability of a pathway for the electric current pulse derived from the applied electric field is proposed as the reason for the achieved shrinkages. Scavenging of the grain boundaries by Joule heating is proposed as the reason for the improved oxide ion bulk conductivity.

A Study and Comparison of the Preparation of Gadolinium Aluminate Nanoparticles Using γ-Irradiated and Unirradiated Precursors

The effects of γ-irradiation and the application of different precursors on the formation of gadolinium aluminate (GdAlO3) nanoparticles (NPs) have been studied in detail. GdAlO3 NPs were prepared by using different gadolinium-based precursors including gadolinium acetate (Gd(CH3COO)3·4H2O) and gadolinium nitrate (Gd(NO3)3·6H2O), while Al2O3 and Al(NO3)3·9H2O were used as the source of Al3+. The preparation of GdAlO3 was carried out by two different methods, solid-state reaction and sol-gel process. To study the effect of γ-irradiation, both irradiated and unirradiated Gd(CH3COO)3·4H2O have been tested for the preparation of gadolinium aluminate (GdAlO3). Notably, Gd(CH3COO)3·4H2O did not produce GdAlO3 in both solid-state and sol-gel processes even after optimizing various parameters, including the application of γ-irradiation. However, single-phase nanocrystalline GdAlO3 NPs were successfully obtained from the reaction of gadolinium nitrate Gd(NO3)3·6H2O and Al(NO3)3·9H2O by a sol-gel process. The formation of NPs has been confirmed by X-ray diffraction analysis (XRD) and Fourier-transform infrared (FT-IR) spectroscopy. The results indicate towards the formation of an orthorhombic perovskite structure of GdAO3 in the Pbnm space group. Transmission electron microscopy (TEM) has been employed for the particle-size analysis, which revealed the formation of spherical-shaped nanoparticles with the size range of 50–70 nm. Surface morphology of the sintered pellet was obtained from high-resolution scanning electron microscopy (HR-SEM). Besides, the effect of irradiation with γ-rays on the quality of resultant NPs has also been studied.

Preparation of High Density BaZr0.97Y0.03O3-δ Ceramic and its Interaction with Titanium Melt

In this paper, the BaZrO3(BZ) and BaZr0.97Y0.03O3-δ(BZY3) powders were prepared by using the industrial grade BaCO3, ZrO2and Y2O3powders combining the conventional solid state reaction. The BaZrO3(BZ) and BaZr0.97Y0.03O3-δ(BZY3) ceramics were fabricated at 1750°C. The effect of ball milling time and sintering aid (TiO2) on the sinterability of BaZr0.97Y0.03O3-δ(BZY3) ceramics were investigated, and the improved stability of BaZrO3refractory with Y2O3additive were studied according to the refractory-metal interaction. The results revealed that the particle size of BZY3 powders decreased first and then increased with the increasing of ball milling time from 6h to 12h, and the minimum particle size was only 2.252μm at 8h. When 2wt.%TiO2was added, the sintered pellet of BZY3 was the most densest and the relative density was above 95%. After melting the Ti2Ni alloy on the BZY and BZ ceramics, the thickness erosion layer of BaZrO3and BZY3refractories and Ti2Ni alloy is approximately 50μm and 20μm respectively, showing that BZY3 was more stable than BaZrO3refractory.

Effect of Sintering Heating Rate on CaCu3Ti4O12 Formation

CaCu3Ti4O12 (CCTO) is an electroceramic material with complex cubic perovskite-like oxide. It possessed a giant dielectric constant of about 105 over a wide temperature range (100-600 K). In this work, CCTO was synthesized through solid state method. The effect of different heating rate during sintering process was studied. The raw materials - CaCO3, CuO and TiO2 were wet ball milled for 24 hours and calcined at 900 °C for 10 hours. Then the calcined powder was pressed into pellet shape at 300 MPa. Sintering was done at 1040 °C for 12 hours with different heating rates: 3, 5 and 10 °C/min. The phase formation and surface morphology was investigated by X-Ray Diffraction (XRD) and Field Emission Scanning Electron Microscope (FESEM), respectively. The density was measured by Archimedes Principle. XRD pattern proves the CCTO single phase formation for the calcined powder and sintered pellet. The SEM images show the different grain size for different heating rate. The density of the pellet was found to be reduced when faster sintering heating rate was used.

Structural, Dielectric and Electrical Characteristic of Bi0.5Pb0.5[Fe0.1La0.4(Zr0.25Ti0.25)]O3

The polycrystalline compound Bi0.5Pb0.5 [Fe0.1La0.4 (Zr0.25Ti0.25)]O3 was synthesized by substituting Pb, La, Zr and Ti ions on perovskite structured bismuth ferrite (BFO) with the help of mixed oxide solid state reaction method. The present work is to observe the effect of off-valence and iso-valence substitution on the dielectric and electric properties of bismuth ferrite (BFO). The room temperature XRD pattern of the calcinated powders of the sample reveals that the crystal structure is tetragonal with space group P4mm, while BFO has rhombohedral structure with space group R3c. The SEM of the sintered pellet of the compound indicates that the small grains are uniformly distributed over the surface. Complex impedance spectroscopy (CIS) was adopted to analyze the dielectric, impedance and conductivity behavior of the compound. The results show that the dielectric loss in the material is significantly less than that of BFO and the dielectric and ferroelectric behavior of the sample get enhanced. The complex impedance plots show the existence of non-Debye type of relaxation phenomena, which is caused by resistive and capacitive effect of the bulk and grain boundaries. The Arrhenius plot for the compound indicates that the material possesses NTCR behavior. The frequency response of ac conductivity obeys Jonscher’s law and UDR (universal dielectric response).[Key words: off-valence, iso-valence, CIS, non-Debye type relaxation, NTCR, UDR]