Investigations of Single Crystal Growth of PbMoO₄

Abstract

The synthesis of polycrystalline PbMoO4 material suitable for use as the starting charge for crystal growth was investigated employing a solid-state sintering method. The solidification behavior of the material was studied by the differential thermal analysis (DTA) technique, with an aim to model the growth by the Czochralski technique. Actual crystal growth runs were carried out to validate the modeling and identify conditions that yield good quality crystals. The results show that large changes in melt stoichiometry, which may arise due to the application of an improperly synthesized starting charge, drive growth from the initial melt growth regime to a self-flux assisted growth regime. The application of a properly synthesized starting charge and the growth direction are found to play a crucial role in determining the quality of the grown crystal.

Non-stoichiometry-induced cracking in PbMoO4 crystals

“…The problem of crystal cracking was investigated in some detail by Bonner and Zydzik [2] and related it to anisotropic thermal contraction of LMO. The subsequent experimental results reported by Takano et al [3], Sabharwal et al [4] and the results of numerical analysis by Miyazaki et al [5] have been found to be in agreement with conclusion of Bonner and Zyzdik. However, it should be mentioned that these results do not comply with the experimental results on sub-grain distribution in LMO, single crystals reported by a number of research groups [3,6,7].…”

“…The melt grown crystals have also been reported to easily crack either during growth or on subsequent handling. In a recent communication, we have reported the growth of LMO crystals free from the presence of macroscopic defects [4]. In that study, the crystal growth parameters and the growth direction were identified which yielded crack-free ingots.…”

“…PbO and MoO 3 taken in the desired proportion and rapidly raising the mixture to the melting temperature. The effect of different sintering temperatures on LMO phase formation has been reported elsewhere [4]. In all the exploratory crystal growth experiments, a charge weighing about 75 g was typically used for the growth of 20 mm diameter and 35 mm long crystals.…”

Optical and X-ray photoelectron spectroscopy of PbGeO3 and Pb5Ge3O11 single crystals

“…The non-stoichiometry manifests in different ways by influencing the optical and other physical properties of the crystal or it may promote the incorporation of impurities during crystal growth (Sabharwal et al 1996(Sabharwal et al , 2006Sabharwal andSangeeta 1999, 2008). The colouration of LGO-2 is related to Pb deficiency as borne out by the present measurements.…”

X-ray absorption spectroscopy of PbMoO4 single crystals

“…A major problem faced with the growth of LMO crystals is the occurrence of non-stoichiometry, which arises due to the excessive vapour pressure of MoO 3 over PbO at elevated temperatures. The preferential and uncontrolled depletion of MoO 3 during growth gives rise to colouration and cracking of the as-grown crystals (Zeng 1996;Bochkova et al 2003;Sabharwal et al 2006;Sangeeta et al 2006;Tyagi et al 2008). The presence of defects arising as a consequence of the stoichiometric deviations is also found to influence the crystal ionic conductivity (Neiman et al 1984).…”