Separation of rare earths from monazite source by ion-exchange process is discussed. Optimum conditions for obtaining kilogram quantities of individual rare earths of high purity are reported.

This paper describes the synthesis and microwave absorption studies of single phase Tl-2223 compound, withT_c=(129 ± 1) K. The single phase compound has been synthesized using a precursor matrix method. It has been found that Tl-deficient starting composition gives the best results.

Coherent inelastic neutron scattering measurements have been carried out on the high temperature superconductors Tl₂CaBa₂Cu₂O₈ (Tl-2122,T_c=107 K) and YBa₂Cu₃O₇ (Y-123,T_c=92 K), at the Dhruva reactor at Trombay. The density of phonon states in Tl-2122 is enhanced at 6–17 meV and reduced at 40–70meV compared to that in Y-123.

Doppler-broadened annihilation radiation spectra have been measured as a function of temperature from 77 K to 300 K, for several high temperature oxide superconductors viz single-phase YBCO, single- and mixed-phase Tl-Ca-Ba-Cu-O and Bi-Ca-Sr-Cu-O compounds. The temperature-dependent parameters extracted respond to a change at the onset of superconducting transition. The observations point to involvement of oxygen valence electrons at the onset of superconducting transition. Also a possible structural change and/or increase in electron density at the oxygen vacancy/defect sites seem to accompany the transition. In addition, the parameters derived are seen to be sensitive to the presence of more than one superconducting phases in mixed phase samples.

A detailed investigation on luminescence properties of gem-grade zirconia (NFC) as a function of Ti doping is presented. The effect of various parameters such as Ti concentration, environment of heat treatment and temperature was studied in detail and the optimum conditions for producing zirconia with luminescence properties comparable to standard material determined.