EQUATION OF STATE OF MGAL2O4 SPINEL TO 65 GPA

Compression measurements on synthetic MgAl2O4 spinel, obtained by quas ihydrostatic x-ray:powder-diffraction at room temperature, are in good agreement with ultrasonically determined values of the-bulk modulus a nd its:pressure derivative at zero pressure. Contrary to previous extr apolations of the ultrasonic data,: from which an elastic (volume) ins tability bad been predicted at similar to 25 GPa, our results show tha t the spinel structure is (meta)stable from 0 to 65 GPa. The zero-pres sure values of the bulk modulus and its pressure derivatives which bes t fit all the available data are K-0,=196(+/-1) GPa, K-0'=4.7(+/-0.3), and K0K0''approximate to-6.