Phases in the System Ba₂SiO₄‐Ca₂SiO₄

Abstract

The system BazSi04-Ca2Si04 was studied by heating mixtures of Ba2Si04 and Ca2Si04 at 1723 K. Six distinct phases resulted; they were examined by both X-ray diffraction and differential thermal analysis. The phases P-(Bao.osCal.es)SiOs and a'-(Bao.lsCal.8s)Si04 are isostructural with corresponding hightemperature modifications of CazSi04. The X phase (B~.,Cal.5zSi04) is orthorhombic, is a pure phase rather than a solid solution, and is defined for the first time in the present work. The T phase (Bal.31Cao.69Si04) is hexagonal and interpreted in terms of a unit cell with a doubled c parameter, in contrast with literature data.

Eu2+–Mn2+ energy transfer in white-light-emitting T-phase (Ba,Ca)2SiO4:Eu2+, Mn2+ phosphor

“…1 shows XRD patterns from Ba 1.20 Ca 0.8 À x À y SiO 4 :xEu 2 + , yMn 2 + with various Eu 2 + /Mn 2 + concentrations, in good agreement with JCPDS card #36-1449, which indicate that all codoped samples are of a single phase called T phase. There is no significant variations of the peak position [10]. When the host lattice is doped with (smaller) Mn 2 + ions, the lattice shrinks as confirmed by a shift of XRD pattern to higher angles by more than a scan step width of 2y =0.021.…”

“…The spectroscopic properties of Mn 2 + ions are strongly influenced by their surrounding local environment, with most Mn 2 + ions substituted in four and six-coordinated sites yielding a strong emission intensity [5,7]. Recently, we found that the only polymorphic phase in which Mn 2 + ions can substitute four or six-coordinated cationic sites, among many possible polymorphic modifications (a 0 L , a 0 H , a, b, g, T, X) of the Eu 2 + /Mn 2 + -codoped T-phase host lattice exhibited red emission from the Mn 2 + ions in addition to green-yellow emission from the Eu 2 + ions [10].…”

Cements obtained from rice hull: Encapsulation of heavy metals

“…The crystalline structure plays an important role in the utilization of these materials [28,29], since the reactivity of ␤-Ca 2 SiO 4 is strongly influenced by the phase present. ␤-phase presents very good adhesive properties.…”

High pressure polymorphism of dicalcium silicate Ca2SiO4. A transmission electron microscopy study

“…Many studics on those polymorphs have been done at ambient conditions, but the phases were always stabilized, generally with BaO, SrO or B2Oa (Ghose et al 1983;Matkovic et al 1986;Thompson et al 1987;Fukuda et al 1992).…”

“…The ~, e~i and c~ polymorphs are stable as pure CazSiO4 only at elevated temperature. These latter phases have been extensively studied at room conditions, but always with the presence of stabilizers (Suzuki and Yamaguchi 1969;Jelenic and Bezjak 1982;Matkovic et al 1986; Thompson et al 1987;Fukuda et al 1992) and uncertainties still exist on their exact structure. The c~ polymorph is considered as a superstructure referring to the c~i phase and two varieties of c~k have been re, ported.…”