A high pressure Raman study of calcium molybdate

Raman and x-ray diffraction investigations on BaMoO4under high pressures

“…To understand the structural stability under different thermodynamic conditions, many scheelite compounds have been extensively studied [5][6][7][8][9][10][11][12]. In particular, under high pressures, the scheelite structured alkaline earth molybdates and tungstates show several phase transitions [7][8][9][10][11][12]. Based on the packing efficiency considerations, some of the earlier studies on these compounds suggested that wolframite [8,13] may be a preferred high pressure structure [14].…”

“…In these scheelite structured compounds (Space Group I4 1 /a, Z = 4), oxygen atoms form a distorted simple cubic arrangement, while the two cations in this structure have fourfold and eightfold coordination with the oxygen atoms. To understand the structural stability under different thermodynamic conditions, many scheelite compounds have been extensively studied [5][6][7][8][9][10][11][12]. In particular, under high pressures, the scheelite structured alkaline earth molybdates and tungstates show several phase transitions [7][8][9][10][11][12].…”

Síntese pelo método da coprecipitação e caracterização estrutural do tungstato de cálcio com estrutura tipo scheelita

“…Os cálculos da teoria de grupo sugerem a presença de 26 diferentes vibrações para cristais de CaWO 4 , que podem ser representados pela equação A [28,29]:…”

“…Entretanto, os modos A g , B g e E g estão relacionados a movimentos de vibração dentro dos cristais de CaWO 4 . Portanto, 13 modos ativos são esperados no espectro de espalhamento Raman para cristais de CaWO 4 , representados pela Equação (B) [28][29][30]. 4 ] e/ou e desordem estrutural no retículo cristalino [20].…”

Investigations of the EPR g Factors for Er3+ in CaMoO4

“…Recently, CaMoO 4 has attracted great interest because of its application in silica-supported catalysts [1], as dispersive element in electronically tunable lasers [2] and mixed electron-hole-ion conductor [3,4]. Particularly, this kind of compounds can be easily doped with rare earth ions and grown to large crystals which are the candidates of solid state laser materials [5,6]. In order to study the electronic energy transfer mechanisms among the rare earth ions as well as the effect of crystal-fields, temperature and pressure on the properties of these materials, extensive investigations have been carried out by means of high pressure Raman and X-ray excited luminescence spectroscopies [7 -9].…”