Untitled

Suvorov, Danilo; Valant, Matjaž; Škapin, Srečo D.; Kolář, D.

doi:10.1023/a:1004341512349

Cited by 54 publications

(16 citation statements)

References 7 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The structure of LaTi 2 Al 9 O 19 was further confirmed by bond valence sum calculations [9]. Although the powder diffraction pattern of La 3 [10][11][12][13][14]. Near field scanning microwave microscopy investigations of LaAlO 3 -TiO 2 diffusion couple showed low dielectric constant value for La 2 Ti 4 Al 18 O 38 [15].…”

Section: Introductionmentioning

confidence: 75%

Dielectric resonators with complex crystal structures in the La2O3–Al2O3–TiO2 system for microwave applications

Dhanya

Unnimaya

Ratheesh

2014

J Mater Sci: Mater Electron

View full text Add to dashboard Cite

LaTi 2 Al 9 O 19 and La 3 Ti 5 Al 15 O 37 ceramics in the La 2 O 3 -Al 2 O 3 -TiO 2 system have been prepared by conventional solid state ceramic route. The structure and microstructure of the compositions have been studied using powder X-ray diffraction and scanning electron microscopic techniques. Laser Raman studies have been employed to understand the complex crystal structure of these compositions in molecular level. The microwave dielectric properties of the sintered ceramic compacts were measured by Hakki and Colemann post resonator and TE 01d cavity techniques using a vector network analyzer. LaTi 2 Al 9 O 19 and La 3 Ti 5 Al 15 O 37 ceramics possess excellent microwave dielectric properties such as relatively high unloaded quality factors 7,762 and 7,415, low dielectric constant 15.7 and 22.1 and low temperature coefficient of resonant frequency values -22 and ?18.9 ppm/°C, respectively.

show abstract

Section: Introductionmentioning

confidence: 75%

Dielectric resonators with complex crystal structures in the La2O3–Al2O3–TiO2 system for microwave applications

Dhanya

Unnimaya

Ratheesh

2014

J Mater Sci: Mater Electron

View full text Add to dashboard Cite

show abstract

“…Bulk density of the sintered specimen was identified by Archimedes' method. Dielectric properties in the microwave frequency range (3)(4)(5) were measured by the dielectric resonator method using a network analyzer (Model N5230A, Agilent, Palo Alto, CA). The quality factor was measured by transmission cavity method using the TE 01d resonant mode.…”

Section: Methodsmentioning

confidence: 99%

“…But compared with numerous examples of ionic conducting perovskites with A-site deficiency, their microwave dielectric properties are relatively less studied. La (2 -x)/3 Na x (Mg 1/2 W 1/2 )O 3 [2], La 2/3 TiO 3 -LaAlO 3 [3], (Pb 1 -3x/2 La x )(Mg 1/2 W 1/2 )O 3 [4], Sr 1 -3x/2 Ce x TiO 3 [5] and CaTiO 3 -La 2/3 TiO 3 [6] are some A-site-deficient perovskites possessing interesting microwave dielectric properties. It was usually found in the A-site-deficient perovskites that the ordering arrangement of A-site cation/ vacancies improved the Q 9 f values.…”

Section: Introductionmentioning

confidence: 99%

Structure and dielectric properties of A-site-deficient perovskite Nd(1 − x)/3M x NbO3 (M = Li, Ag; 0 ≤ x ≤ 0.20) ceramics

2012

View full text Add to dashboard Cite

Crystal structure and dielectric properties of the A-site-deficient perovskites Nd (1 -x)/3 M x NbO 3 (M = Li, Ag; 0 B x B 0.20) ceramics were investigated with X-ray diffractometer (XRD), network analyzer, and impedance analyzer. XRD results showed that no secondary phase was observed for Ag-doped specimens. However, a second phase LiNdNb 2 O 7 appeared for Li-doped ones when x C 0.16. The crystal structure at room temperature transformed from orthorhombic (0 B x \ 0.16) into tetragonal symmetry (0.16 B x B 0.20) with the increase of x. Complex impedance analysis and the dielectric properties measured at low frequency showed that the dielectric loss in Nd (1 -x)/3 M x NbO 3 (M = Li, Ag; 0 B x B 0.20) at low frequency was mainly caused by the lithium or silver ionic conduction, which increased with the increase of temperature. However, the dielectric loss originated from the ionic conductivity was frozen at microwave frequency. The dielectric constant (e r ) increased with the addition of Ag, whereas it decreased with the increase of Li addition. The pure and Ag-doped specimens exhibited large positive temperature coefficient of resonant frequency (s f ), while the s f value changed from positive into negative with the increase of Li addition. The Q 9 f value increased from 437 to 1,110 GHz in the case of Li doping and 765 GHz in the case of Ag doping, respectively, when x increased from 0 to 0.12. Further increase in x decreased the Q 9 f values both for the Li-and Ag-doped specimens. Good combined microwave dielectric properties with e r = 153, Q 9 f = 1,110 GHz and s f = -45 ppm/°C could be obtained for the Li-doped specimen when x = 0.12.

show abstract

“…3) La 2=3 TiO 3 has become an interesting dielectric material after it was stabilized by Ni, 4) Pb, 5) Al, [6][7][8] or Nb 9) et al For example, La 2=3 TiO 3 doped with 4% LaAlO 3 has attractive microwave properties: " r ¼ 61:9, Q Â f ¼ 23900 GHz and f ¼ 123 ppm/ C. 7) The value of f of such materials can be adjusted to zero by preparation of solid solution with compounds having negative temperature coefficient of resonant frequency. 10,11) As it has reported, La(Mg 0:5 Ti 0:5 )O 3 ceramics was a promising microwave material for application of dielectric resonators and filters.…”

Section: Instructionmentioning

confidence: 99%

Microwave Dielectric Properties of the (1−x)La2&frasl;3TiO3–xLa(Ti1&frasl;2Mg1&frasl;2)O3 System

et al. 2006

View full text Add to dashboard Cite

(1 À x)La 2=3 TiO 3 -xLa(Mg 1=2 Ti 1=2 )O 3 ceramics with x ranging from 0.1 to 0.9 were prepared by conventional solid-state reaction. La 2=3 TiO 3 and La(Mg 1=2 Ti 1=2 )O 3 were found to form a solid solution over the whole compositional range. However, the second phase La 2 Ti 2 O 7 existed for x ¼ 0:1 and 0.3. As the x value increased from 0.1 to 0.9, the dielectric constant " r decreased from 65.1 to 28.4. The oxygen vacancies were the main factor affecting the Q Â f values of the (1 À x)La 2=3 TiO 3 -xLa(Mg 1=2 Ti 1=2 )O 3 ceramics. A f value of À5 ppm/ C can be obtained at x ¼ 0:3. Keywords: microwave ceramic, dielectric properties, La 2=3 TiO 3 , La(Mg 1=2 Ti 1=2 )O 3 InstructionRecently, the development of microwave applications, including mobile telephones and satellite communication systems, makes rapid progress due to the improved performance of dielectric resonators and filters. Requirements of microwave dielectric ceramics used as dielectric resonators and filters are combined with high dielectric constant (" r ), high quality factor (Q) and near-zero temperature coefficient of resonant frequency ( f ).1,2) These three parameters are correlated to the size, frequency selectivity and temperature stability of the microwave electronic component.La 2=3 TiO 3 is a perovskite compound with general formula ABO 3 . It is unstable in its pure form due to the high content of vacancies in the A cationic sublattice.3) La 2=3 TiO 3 has become an interesting dielectric material after it was stabilized by Ni, 4) Pb, 5) Al, [6][7][8] or Nb 9) et al. For example, La 2=3 TiO 3 doped with 4% LaAlO 3 has attractive microwave properties: " r ¼ 61:9, Q Â f ¼ 23900 GHz and f ¼ 123 ppm/ C. 7) The value of f of such materials can be adjusted to zero by preparation of solid solution with compounds having negative temperature coefficient of resonant frequency. 10,11) As it has reported, La(Mg 0:5 Ti 0:5 )O 3 ceramics was a promising microwave material for application of dielectric resonators and filters.12,13) It exhibits dielectric constant of 28, Q Â f of 631000 GHz and negative f of À79 ppm/ C. The purpose of the present work thus is to stabilize La 2=3 TiO 3 and adjust the f of La 2=3 TiO 3 by introducing La(Mg 0:5 -Ti 0:5 )O 3 . The sintering and microwave dielectric properties of (1 À x)La 2=3 TiO 3 -xLa(Mg 1=2 Ti 1=2 )O 3 were also investigated. ExperimentIn this work, the La 2 O 3 , TiO 2 and MgO powders were mixed according to the compositions (1 À x)La 2=3 TiO 3 -xLa(Mg 1=2 Ti 1=2 )O 3 (x ¼ 0:1; 0:3; 0:5; 0:7; 0:9) and milled with ZrO 2 balls for 24 h in ethanol and then dried at 120 C for 10 h. The dried powders were calcined at 1250 C for 3 h. A small mount of Al 2 O 3 was added as sintering aid. The calcined powders were milled again for 24 h and dried at 120 C for 10 h. After the dried powders doped with 7 mass% polyvinyl alcohol (PVA) were preformed using cylindrical mold of 16 mm diameter, they were pressed at 2000 kg/cm 2 with cold-isostatic pressing. The pellets were sintered at 1400-1600 C for 3 h in air w...

show abstract

Untitled

Cited by 54 publications

References 7 publications

Dielectric resonators with complex crystal structures in the La2O3–Al2O3–TiO2 system for microwave applications

Dielectric resonators with complex crystal structures in the La2O3–Al2O3–TiO2 system for microwave applications

Structure and dielectric properties of A-site-deficient perovskite Nd(1 − x)/3M x NbO3 (M = Li, Ag; 0 ≤ x ≤ 0.20) ceramics

Microwave Dielectric Properties of the (1−<I>x</I>)La<SUB>2&frasl;3</SUB>TiO<SUB>3</SUB>–<I>x</I>La(Ti<SUB>1&frasl;2</SUB>Mg<SUB>1&frasl;2</SUB>)O<SUB>3</SUB> System

Contact Info

Product

Resources

About

Untitled

Cited by 54 publications

References 7 publications

Dielectric resonators with complex crystal structures in the La2O3–Al2O3–TiO2 system for microwave applications

Dielectric resonators with complex crystal structures in the La2O3–Al2O3–TiO2 system for microwave applications

Structure and dielectric properties of A-site-deficient perovskite Nd(1 − x)/3M x NbO3 (M = Li, Ag; 0 ≤ x ≤ 0.20) ceramics

Microwave Dielectric Properties of the (1&minus;<I>x</I>)La<SUB>2&frasl;3</SUB>TiO<SUB>3</SUB>&ndash;<I>x</I>La(Ti<SUB>1&frasl;2</SUB>Mg<SUB>1&frasl;2</SUB>)O<SUB>3</SUB> System

Contact Info

Product

Resources

About

Microwave Dielectric Properties of the (1−<I>x</I>)La<SUB>2&frasl;3</SUB>TiO<SUB>3</SUB>–<I>x</I>La(Ti<SUB>1&frasl;2</SUB>Mg<SUB>1&frasl;2</SUB>)O<SUB>3</SUB> System