Crystal structure of lead tungstate at 1.4 and 300 K

Abstract

The crystal structure of lead tungstate, PbWO 4 , is tetragonal, scheelite type, space group I4 1 /a. This compound is frequently subjected to lead deficiency, due to the difference in the vapour pressure of the two oxides, WO 3 and PbO, used in the crystal growth. One group has reported that lead vacancies can order in a crystal structure derived from the scheelite type, but of lower symmetry and described by the space group P4/nnc or 4 P .We report here on neutron diffraction measurements performed on three different powdered samples. Our measurements do not show any indication of structural transition between 1.4 and 300 K. The structure is undoubtedly the tetragonal one. The existence of a lead deficient structure remains unconfirmed.

Effects of pressure on PbWO4-III

“…The existence of two intense diffraction lines located near 11°-12°shows distinct difference from one intense broad peak of the proposed PbWO 4 -III by Errandonea et al (2006b). Compared with the crystal diffraction data of PbWO 4 -III and PbWO 4 -I (Richter et al 1976;Chipaux et al 2001), our powder ADXRD patterns indicate that the grinding powder sample includes two phases. The calculated positions of the diffraction peaks of the tetrahedral PbWO 4 -I and the monoclinic PbWO 4 -III are indicated by arrows and tick marks in Fig.…”

“…The intensity of new Raman peak increases with increase in the grinding time. The powder X-ray diffraction indicates that the additional new phase, which was produced by grinding process, belongs to the scheelite-structured PbWO 4 -I (Chipaux et al 2001;Richter et al 1976). The synthesized crystal and fine grinding powder were used for our Raman and synchrotron angledispersive X-ray diffraction (ADXRD) measurements, respectively.…”

“…Under ambient conditions, there are three types of polymorphs for PbWO 4 compound: the tetrahedral stolzite (PbWO 4 -I, I4 1 /a, Z = 4), which has a same structure with the scheelite (CaWO 4 ), the monoclinic raspite (PbWO 4 -II, P2 1 /a, Z = 4) and the metastable monoclinic PbWO 4 -III (P2 1 /n, Z = 8) (Chipaux et al 2001;Li et al 2003). For their crystal structures, stolzite has isolated WO 4 tetrahedra with the Pb atom being eight-coordinated by the oxygen atoms (Chang 1971).…”

Paramagnetic defects in manganese-doped lead tungstate

“…The space group of the crystal at temper atures of 300 K and 1.4 K is I4 1 /a ( ), and the local symmetry of the Pb 2+ and W 6+ positions is S 4 [33,34]. In this respect, the assertion made by the authors of [23,30] that the position of the ion tungsten has the symmetry group D 2d is obviously erroneous.…”

Microwave dielectric properties of two low temperature sintering ceramics in the PbO–WO3 binary system

“…In the PbO À WO 3 system the existence of two binary compounds PbWO 4 and Pb 2 WO 5 was reported [14]. The two compounds have isolated tungsten groups with the tungsten in tetrahedral coordination [15,16] …”