The thermal properties of two heteropoly complexes a- [ (C7H15) 4N]3H2[SiW11 (NbO2) O39] H2O and a-[ (C7H15)4N]4 [PW11 (NbO2). O39] H2O were studied by means of TG DTA and DSC. The activation energies and reaction ord...The thermal properties of two heteropoly complexes a- [ (C7H15) 4N]3H2[SiW11 (NbO2) O39] H2O and a-[ (C7H15)4N]4 [PW11 (NbO2). O39] H2O were studied by means of TG DTA and DSC. The activation energies and reaction orders of the thermal decomposition reaction of these complexes have been calculated.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
文摘The thermal properties of two heteropoly complexes a- [ (C7H15) 4N]3H2[SiW11 (NbO2) O39] H2O and a-[ (C7H15)4N]4 [PW11 (NbO2). O39] H2O were studied by means of TG DTA and DSC. The activation energies and reaction orders of the thermal decomposition reaction of these complexes have been calculated.
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.
