Effect of ambient water on crystal morphology and coloration of lead molybdate

Abstract

Vapour phase growth of two types of lead molybdate (PbMoO4) crystals has been studied in air under normal pressure. It has been found that both PbMoO4 crystal morphology and crystal coloration depend sensitively on water content in ambient air. Using dry air, the resultant PbMoO4 is mainly in form of needles growing along 〈001〉 directions of the crystal whereas in an atmosphere of moisturized air, the product is mostly terrace-like platelets, extending towards 〈110〉 directions. The PbMoO4 needle crystals are found with light-yellow colour while the platelet crystals are light-grey or colourless. Considerations of growth have also been given to the observed two types of PbMoO4 crystals.