A niobate was synthesized by doping Bi3＋ in the ternary system BaO- N O- Nb2O5. The crystal structure was determined by X- ray powder diffraction,and it belongs to tetragonal tungsten bronze structure at room tempera...A niobate was synthesized by doping Bi3＋ in the ternary system BaO- N O- Nb2O5. The crystal structure was determined by X- ray powder diffraction,and it belongs to tetragonal tungsten bronze structure at room temperature with unit cell parameters a=1.24777 (2) nm,c=0.39266(1) nm,α =β =γ =90° .Measurements of dielectric properties indicate that phase transitions of Ba3NaBiNb10O30 from paraelectric to ferroelectric occurs at 400℃ ,which is lower than that of B NaNb5O30.展开更多
A New Niobate Ba 5LaTi 2Nb 3O 18 was synthesized by a high temperature solid state reaction in the BaO-La 2O 3-TiO 2-Nb 2O 5 system. The chemical compositions, crystal structure, microstructure, density and melting po...A New Niobate Ba 5LaTi 2Nb 3O 18 was synthesized by a high temperature solid state reaction in the BaO-La 2O 3-TiO 2-Nb 2O 5 system. The chemical compositions, crystal structure, microstructure, density and melting point of the new compound were characterized by EPMA, XRD, SEM, DTA and so on. Ba 5LaTi 2Nb 3O 18 crystallizes the rhombohedral system with unit cell parameters a=0 573 25(2) nm, c=4 213 9(2) nm, and space group R3m, Z=3. The structure may be described as five (Nb,Ti)O 6 octahedra corner-sharing along c axis to form perovskite layer connected by Ba atoms. The Ba 5LaTi 2Nb 3O 18 ceramic exhibits a high dielectric constant of 80.5, low dielectric loss of 6.5×10 -4 and small temperature coefficient of dielectric constant of -78×10 -6 K -1 at 1 MHz due to its close structure and relative high dielectric polarizabilities of Ba 2+, La 3+, Ti 4+ and Nb 5+. Ba 5LaTi 2Nb 3O 18 might be a suitable candidate of high ε r microwave dielectric ceramics.展开更多
A series of alumina-pillared layered titanoniobates with different interlayer distances were first prepared by using a step-wise exchange process. The effect of reaction conditions such as reaction temperature, reacti...A series of alumina-pillared layered titanoniobates with different interlayer distances were first prepared by using a step-wise exchange process. The effect of reaction conditions such as reaction temperature, reaction time, ageing time of pillaring agent, and molar ratio of two reactans was exmained. The resultat pillazed smples have a range of interlayer distances from 1.23 nm to 1.38nm, and are thermostable over 500展开更多
文摘A niobate was synthesized by doping Bi3＋ in the ternary system BaO- N O- Nb2O5. The crystal structure was determined by X- ray powder diffraction,and it belongs to tetragonal tungsten bronze structure at room temperature with unit cell parameters a=1.24777 (2) nm,c=0.39266(1) nm,α =β =γ =90° .Measurements of dielectric properties indicate that phase transitions of Ba3NaBiNb10O30 from paraelectric to ferroelectric occurs at 400℃ ,which is lower than that of B NaNb5O30.
文摘A New Niobate Ba 5LaTi 2Nb 3O 18 was synthesized by a high temperature solid state reaction in the BaO-La 2O 3-TiO 2-Nb 2O 5 system. The chemical compositions, crystal structure, microstructure, density and melting point of the new compound were characterized by EPMA, XRD, SEM, DTA and so on. Ba 5LaTi 2Nb 3O 18 crystallizes the rhombohedral system with unit cell parameters a=0 573 25(2) nm, c=4 213 9(2) nm, and space group R3m, Z=3. The structure may be described as five (Nb,Ti)O 6 octahedra corner-sharing along c axis to form perovskite layer connected by Ba atoms. The Ba 5LaTi 2Nb 3O 18 ceramic exhibits a high dielectric constant of 80.5, low dielectric loss of 6.5×10 -4 and small temperature coefficient of dielectric constant of -78×10 -6 K -1 at 1 MHz due to its close structure and relative high dielectric polarizabilities of Ba 2+, La 3+, Ti 4+ and Nb 5+. Ba 5LaTi 2Nb 3O 18 might be a suitable candidate of high ε r microwave dielectric ceramics.
文摘A series of alumina-pillared layered titanoniobates with different interlayer distances were first prepared by using a step-wise exchange process. The effect of reaction conditions such as reaction temperature, reaction time, ageing time of pillaring agent, and molar ratio of two reactans was exmained. The resultat pillazed smples have a range of interlayer distances from 1.23 nm to 1.38nm, and are thermostable over 500
