Phase equilibrium relations in the binary system bismuth sesquioxide-niobium pentoxide

Abstract

T~e phase eq ui libr. iu m diag ram fo r th c binary sy ste m bis mu t h sesq uioxide-niobium pentoxlde has been cO llsLru cted from obse rvaL iolls of fu sion characteristics a nd X-ray diffracbon data. In t he syste m fi ve blila ry compounds were obse rved wi t h Bi20 3 :NbzOs ratios of .5: 3, 1 : 1. 4: D, 1: 5, a nd 1 : 6. The 1: 1 co mpo und was fou nd to Lransform irreversibl y (Ill la borator y t une) from t he ort horh ombic bis l11u totantali tc typc st ruc t ure to a tricli nic fo rm at about 1,020 °C and me lt congrue ntl y at J ,24 . 5 °C. The 5:3 com pound melts in congru e nt ly at 1,193 °C t he 4: 9 at 1,183 °C a nd the 1: 6 at 1,242 °C. The J : 5 co mpou nd h as a max imum t e mpe rat ure of stab ili ty at 1,095 °C alld Liw 4:9 a nd J: 6 co mpound have minimum te mperatures o~ st~b ili~y at 1,070 °C and 1, 002 °C res pectivc ly. Nb20 s was found to ?ntcr m to sohd solu tIOn In BI20 ,! up t? about 23 .5 mo le pc rce nt Nb20 s. The me lting p oint I S lllcreased and the monoc linic-cub ic phasc t ra ns form ation tem perat ure is decreased . A morphotropIC phase change OCC UlTS at about 19.5 mole pe rccnt NbzOs from the cubic to a p se udocu bic st ru cture .

Photodegradation of BiNbO4 Powder during Photocatalytic Reactions

“…5 We report here a study of BiNbO 4 as a photocatalyst, its problems due to photodegradation, and a facile solution to that limitation. BiNbO 4 exists in two polymorphs, a low temperature orthorhombic (R) phase 6,7 and a high temperature triclinic ( ) phase. 8 An irreversible (in powders) 9 phase transition occurs from the R phase to the phase at ∼1020°C.…”

“…8 An irreversible (in powders) 9 phase transition occurs from the R phase to the phase at ∼1020°C. 6,7,[10][11][12] The greatest interest in BiNbO 4 is as a promising dielectric material, 13,14 and only a limited amount of research has been directed toward its photocatalytic capabilities. [15][16][17][18] Both phases have a layered structure that consist of vertex-sharing NbO 6 octahedra, 10,12 but the low temperature orthorhombic (R) phase shows the greater photocatalytic activity.…”

Synthesis and microwave dielectric behavior of (Bi1−xPbx)NbO4ceramics

“…However, a large scatter in Q u .f (1800-17,000 GHz) exists amongst the reported literature. 1,5,6,9 Some of the earlier interesting reports on polycrystalline BiNbO 4 include BiNbO 4 ceramics with sintering aids such as (i) CuO (0.125-1.5 wt.%) 8 and (ii) V 2 O 5 (0.125-1.5 wt.%) to improve " 0 r and Q u .f. 7 Subsequently, several researchers attempted to modify the quality factor (Q u .f ) and the f (temperature coefficient of resonant frequency) by discretely substituting La 3þ , Sm 3þ , Nd 3þ , Dy 3þ or Y 3þ in place of Bi 3þ5,10-14 and Ta 5þ or Sb 5þ in place of Nb 5þ .…”

“…P). 8 Kageta et al 6 reported the dielectric properties of BiNbO 4 ceramics at microwave frequency for the first time, i.e., dielectric constant " 0 r $ 43, quality factor Q $ 4260 (at 4.3 GHz). However, a large scatter in Q u .f (1800-17,000 GHz) exists amongst the reported literature.…”

Microwave Dielectric Properties of Ti-Te system Ceramics for Triplexer Filter

“…In addition, loss of resistance of the internal conductor in multi-layered devices significantly affects the performance of such devices within the microwave range of several hundred MHzs. An internal conductor should utilize materials with high conductivity, such as silver (Ag, m.p.=961 o C) or copper (Cu, m.p.=1064 o C) [5,6]. In case that Low Temperature Cofired Ceramics (LTCC) technology is applied for device manufacturing, sintering of dielectric material should be conducted at a temperature, which is less than the melting point of conducting metal.…”