GROWTH AND PROPERTIES OF FERROELECTRIC LEAD HYDROGEN PHOSPHATE AND LEAD NITRATE PHOSPHATE SINGLE-CRYSTALS

Ferroelectric lead hydrogen phosphate (LHP) and lead nitrate phosphate (LNP) single crystals are grown together by slow diffusion of lead nitrate by sodium metasilicate gels impregnated with orthophosphoric acid. A description of the material preparation, growth procedure and crystal nucleation, is given. Bright and transparent prismatic LHP crystals up to 7 multiplied by 4 multiplied by 3 mm**3 and LNP crystals up to 12 multiplied by 6 multiplied by 3 mm**3 in size are obtained. It is observed that the growth rate of the LNP crystals is faster than that of the LHP crystals. Results obtained on characterization of these two crystals chemical, and on analysis, X-ray diffraction, EDAX, etc. are reported. The microhardness and Young modulus are determined. The average density of dislocations has been determined by employing the chemical etching technique and found to be 3 multiplied by 10**2 cm** minus **2 in LHP and 7 multiplied by 10**2 cm** minus **2 in LNP crystals. The implications are discussed.