Optical properties of CaWO₄ and CaMoO₄ crystals in the 4 to 25 eV region

Abstract

The reflection spectra of CaWO, and CaMoO, single crystals were measured in the region between 4 and 25 eV. The measurements were performed using the electron synchrotron DESY as a light source. Both crystals show very similar spectral features. A relatively sharp, well separated low energy peak is accompanied on the high energy side by two groups of maxima, each group containing three broad main reflection bands which strongly overlap. Besides this, a less pronounced structure is observed over the whole spectral region.The experimental results are discussed in terms of semiempirical MO calculations of the anionic transition metal complexes.Die Reflexionsspektren von CaW0,-und CaMo0,-Einkristallen wurden zwischen 4 und 25 eV gemessen. Das Elektronensynchrotron DESY diente als Lichtquelle. Die Spektren der beiden Kristalle sind sehr Sihnlich. Ein relativ scharfer, wohl getrennter, niederenergetischer Peak wird zu kiirzeren Wellenlangen hin jeweils von zwei Bandengruppen gefolgt, die im wesentlichen aus drei sich stark uberlappenden Maxima aufgebaut sind. Daneben ist iiber den ganzen Spektralbereich eine weniger ausgepragte Struktur zu beobachten. Die experimentellen Ergebnisse werden mit Hilfe semiempirischer MO-Berechnungen der Anionenkomplexe diskutiert.

Comparative study of optical spectra and electronic structures of CaMoO4 and CaWO4 crystals

“…In the optical spectra of scheelite crystals other than PbWO 4 , the lowest absorption band is observed at around 6 eV for tungstates such as CaWO 4 and BaWO 4 [9,15], and at around 5 eV for molybdates such as CaMoO 4 , CdMoO 4 and BaMoO 4 [15][16][17]. The lowest absorption band in CaWO 4 was assigned to the transition to the 1s exciton state [14], since the peak position locates below the threshold energy (7.0 eV) for photo-excitation of free carriers to induce thermoluminescence (TL) [18].…”

Localized excitons and defects in PbWO4 single crystals: a luminescence and photo‐thermally stimulated disintegration study

“…Luminescence of single crystals of lead tungstate was studied in the 1970s [1,2] and became a subject of renewed interest about ten years ago when this material was chosen for high energy physics detectors [3]. The recent results, obtained in the study of its scintillation characteristics and material optimization, were reviewed in [4,5].…”

Electrical and Vibrational Studies of Na2K2Cu(MoO4)3

“…In these materials, the anionic framework is usually built from MoO 4 tetrahedra linked to the transition metal polyhedra, leading to a large variety of crystal structures with a high capacity for cationic substitution. The chemistry of inorganic molybdate materials has been significantly advanced thanks to their valuable electrical and optical properties, which make them promising for various applications such as photoluminescence [1], ionic conductivity [2][3][4], laser materials [5,6], and piezoelectrics [7]. The high-temperature superconductivity present in the copper-oxygen ceramic systems resulted in an increasing structural and physicochemistry interest of materials containing Cu-O [8].…”