scholarly journals Influence of mechanical activation on synthesis and properties of the MgO-TiO2 system

2007 ◽  
Vol 39 (1) ◽  
pp. 59-65 ◽  
Author(s):  
Vera Petrovic ◽  
A. Maricic ◽  
N. Labus ◽  
M.M. Ristic
Keyword(s):  
Dielectric Properties ◽  
Mechanical Activation ◽  
Microwave Dielectric Properties ◽  
Particle Morphology ◽  
Dielectric Materials ◽  
Magnesium Carbonate ◽  
High Energy ◽  
Crystal Modification ◽  
Type I ◽  
Microwave Dielectric

Materials applied in electronics such as multilayer capacitors are an important field of ceramic materials. Magnesium titanate based dielectric materials are used for producing type-I capacitors. A common way of obtaining this material is a solid-state reaction during reaction sintering. The process of sintering can be enhanced if mechanical activation precedes. In this work starting powders of magnesium carbonate (MgCO3) and titanium dioxide (TiO2) with a rutile crystal modification were weighed to attain a 1:1 molar MgCO3:TiO2 ratio. Mechanical activation of the starting mixture was performed by high energy ball milling using ZrO balls and vessels with a ball to powder mass ratio of 40:1. The observed grinding times were 15, 30, 60 and 120 minutes. Powder characterization was conducted using X ray powder diffraction, DTA analysis up to 1000 o C and particle morphology changes were observed with Scanning Electron Microscopy. Isothermal sintering of compacted powders was conducted at 1100?C during 30, 60 and 180 minutes. For specimens synthesized in such a manner, microwave dielectric properties were measured, quality factor Q, specific electrical resistivity (?) and the dielectric constant (?r). In this work we explain the influence of mechanical activation on the MgCO3-TiO2 system leading to titanate formation during sintering, as well as induced changes in microwave dielectric properties.

Effect of Syntesis and Frequency on Electrical Properties on Dielectric Ceramics MgCO3-TiO2

2014 ◽  
Vol 875-877 ◽  
pp. 1554-1559
Author(s):  
Vera V. Petrovic ◽  
Hranislav Milosevic
Keyword(s):  
Mechanical Activation ◽  
Microwave Dielectric Properties ◽  
Dielectric Materials ◽  
Magnesium Carbonate ◽  
High Energy ◽  
Crystal Modification ◽  
Type I ◽  
Mode Amplitude ◽  
Starting Mixture ◽  
Microwave Dielectric

Magnesium titanate based dielectric materials are used for producing type-I capacitors. A common way of obtaining this material is a solid-state reaction. The process of sintering can be enhanced if mechanical activation preceedes. In this work starting powders of magnesium carbonate (MgCO3) and titanium dioxide (TiO2) with a rutile crystal modification were weighed to attain a 1:1 molar MgCO3:TiO2. Mechanical activation of the starting mixture was performed by high energy ball milling using ZrO balls and vessels with ball to powder mass ratio 40:1. The observed grinding times were 15, 30, 60 and 120 minutes. The isothermal sintering of compacted powders was conducted at 1100°C during 30, 60 and 180 minutes. For specimens synthesized in such a manner, microwave dielectric properties were measured, quality factor Q and the dielectric constant (εr) in function of frequency. The measurements of electrical resistivity, capacitance and loss tangent of samples were measured in the frequency range from 500 Hz to 5 MHz frequencies with a HIOKI 3532-50 LCR HiTESTER device at a constant voltage mode (amplitude 0.5 V of sinusoidal signal applied to the specimens).

B-O Bond Character and Microwave Dielectric Properties of (1-x)CaTiO3-xCa(Zn1/3Nb2/3)O3 Perovskite Ceramics

2009 ◽  
Vol 421-422 ◽  
pp. 69-72
Author(s):  
Jie Shen ◽  
Wen Chen ◽  
Jing Zhou ◽  
Jie Zhu ◽  
Qiong Lei
Keyword(s):  
Dielectric Constant ◽  
Dielectric Properties ◽  
Microwave Dielectric Properties ◽  
Dielectric Materials ◽  
Solid State Reaction Method ◽  
Dielectric Constants ◽  
Identical Result ◽  
Microwave Dielectric ◽  
Calculation Results ◽  
The Relationship

The relationship between the character of the B-site cation–oxygen bond and the microwave dielectric properties in perovskites dielectric materials was studied in this paper. The atomic net charge of CaTiO3 (CT) and Ca(Zn1/3Nb2/3)O3 (CZN) was calculated respectively. The calculating result implies that the covalency of B-O bonds in CZN is stronger than that in CT. This predicted that the dielectric constant and loss of the ceramics will decrease after CZN incorporated in CT. To confirme the prediction, (1-x)CT-xCZN microwave dielectric ceramics were prepared by solid state reaction method with ZnNb2O6 as precursor. The structure analysis in terms of tolerance factor gives an identical result as calculation. The microwave dielectric properties, such as dielectric constants, Q×f values and τf were studied as a function of composition. With x increasing from 0.2 to 0.8, the dielectric constant linearly decreases from 109 to 49.37, the Q×f value increases from 8,340 to 13,200 GHz, and τf decreases from 321 to -18 ppm/°C. The properties trends are consistent with the previous calculation results, and confirm the relationship between the character of B-O bond and dielectric properties.

Microwave Dielectric Properties of MgNb2O6 Ceramics Prepared via High Energy Ball Milling Method

2013 ◽  
Vol 631-632 ◽  
pp. 499-503
Author(s):  
Zhi Fen Fu ◽  
Jian Li Ma ◽  
Peng Liu ◽  
Yong Xin Tang
Keyword(s):  
Dielectric Properties ◽  
Ball Milling ◽  
Microwave Dielectric Properties ◽  
High Energy ◽  
High Energy Ball Milling ◽  
Potential Candidate ◽  
Conventional Solid State Reaction ◽  
Microwave Dielectric ◽  
Milling Method ◽  
Energy Ball

The effects of high-energy ball milling and subsequent calcinations on the mixture of MgO and Nb2O5 are investigated. It is found that the pure MgNb2O6 phase can be synthesized at 800 °C for 5 h by using high-energy ball milling method. MgNb2O6 ceramics were prepared at 1220 °C by using calcined powders of milled 15 h, which is lower 100 °C than that required by using the conventional solid state reaction method. The microwave dielectric properties of MgNb2O6 ceramic with εr = 19.7 and Qf = 29 044 GHz were obtained by the High-energy ball milling method, which made it a potential candidate for application.

The effects of high-energy ball milling on the synthesis, sintering and microwave dielectric properties of Li2TiO3 ceramics

2018 ◽  
Vol 29 (13) ◽  
pp. 10933-10941 ◽  
Author(s):  
Somaye Ghaffari ◽  
Touradj Ebadzadeh ◽  
Masoud Alizadeh ◽  
Keivan Asadian ◽  
Yadolah Ganjkhanlou ◽  
...  
Keyword(s):  
Dielectric Properties ◽  
Ball Milling ◽  
Microwave Dielectric Properties ◽  
High Energy ◽  
High Energy Ball Milling ◽  
Microwave Dielectric ◽  
Energy Ball
Sign in / Sign up

Export Citation Format

Share Document