Development and validation of energy dispersive x‐ray fluorescence method for quantification of cubic zirconia in diamond matrix

Qualitative and quantitative tests of gemstones and diamonds are routinely performed nondestructively in the laboratory of Gemmological Institute of India (GII), Mumbai, India. Qualitative tests are based on microscopic examination. Energy Dispersive X‐Ray Fluorescence (EDXRF) spectrometry is used in the laboratory for quantitative analysis of elements. However, in some cases like determination of trace levels of cubic zirconia (CZ) in diamond powder, it is difficult to estimate simultaneously both CZ and diamond powder directly using EDXRF method. In view of this, a method was developed for estimation of ZrO2 present at low levels in diamond powder. In this method, EDXRF spectra of a series of simulated mixtures containing ZrO2 were measured. Peak areas under the characteristic Kα x‐ray of Zr (15.7 keV) in each mixture were computed and, a calibration plot was made between the peak areas and % fractions of ZrO2. From the calibration plot, a dynamic range of 0.1%–10% was obtained. From XRF spectra of the test sample, in duplicate, of diamond powder, Zr was estimated using the peak area and the percentage fraction was found to be 0.181 ± 0.020. Neutron activation analysis (NAA) was used for method validation with the same set of simulated samples used in EDXRF analysis. Results obtained by both the methods are found to be in good agreement and this newly developed method based on EDXRF spectrometry is in regular use in GII.