K G Subhadra
Articles written in Bulletin of Materials Science
Volume 23 Issue 2 April 2000 pp 147-150 Mechanical Properties
In view of discrepancies in the available information on the hardness of lithium niobate, a systematic study of the hardness has been carried out. Measurements have been made on two pure lithium niobate crystals with different growth origins, and a Fe-doped sample. The problem of load variation of hardness is examined in detail. The true hardness of LiNbO3 is found to be 630 ± 30 kg/mm2. The Fe-doped crystal has a larger hardness of 750 ± 50 kg/mm2.
Volume 24 Issue 5 October 2001 pp 469-473 Crystal Growth
Microhardness measurements were undertaken on twelve rare earth garnet crystals. In yttrium aluminium garnet and gadolinium gallium garnet, there was no measurable difference in the hardness values of pure and nominally Nd-doped crystals. The hardness values were correlated with the lattice and elastic constants. An analysis of hardness data in terms of the interatomic binding indicated a high degree of covalency.
Volume 25 Issue 1 February 2002 pp 31-35 Mechanical Properties
Vickers hardness measurements have been made on polycrystalline blanks of CsCl𝑥Br(1–x) and single crystals of NH4Cl𝑥Br(1–x). The composition dependence of hardness is highly nonlinear in both systems and follows an empirical model that includes a lattice contribution and a disorder contribution. The Gilman–Chin parameter (𝐻/𝐶44) has been calculated and its significance discussed.
Volume 25 Issue 3 June 2002 pp 203-207 Mechanical Properties
Vickers and knoop hardness measurements were carried out on CsBr and CsI single crystals. Polycrystalline blanks of CsCl, CsBr and CsI were prepared by melting and characterized by X-ray diffraction. Vickers hardness measurements were carried out on these blanks. The hardness values were correlated with the lattice constant and the Schottky defect formation energy.
Volume 26 Issue 2 February 2003 pp 261-265 Mechanical Properties
Efforts are made to improve the hardness of rubidium halide crystals by
solid solution hardening and
Systematic microhardness measurements have been made on rubidium halide mixed crystals (RbBr–RbI and KI–RbI) and rubidium halide crystals doped with Sr2+ ions. The composition dependence of the hardness of mixed crystals follows the law $\Delta H_V$ = $K\ x$ (1–𝑥), where $\Delta H_V$ is the enhancement in hardness, 𝐾 a constant and 𝑥 and (1 – 𝑥) the concentrations of the first and second component of the mixed crystals, respectively. The hardness of doped crystals increases with the concentration 𝐶 of the dopant according to the law, $\Delta H_V$ = $k\ C^m$, where 𝑘 and 𝑚 are constants. The relative efficacy of the two methods of hardening is discussed.
Volume 42 | Issue 6
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