Glass-formation in binary vanadate systems

Abstract

In accordance with classical concepts about glass-forming capacity, V205 is referred to the conditional glass-formers, which do not vitrify independently under normal conditions of quenching. As Stanworth [1] noted recently, substances such as V205, TeO2, MOO3, and Sb203 may be obtained in a vitreous state, due to the fact that they possess sufficiently open and adequately convalent network structures. Sarjeant and Roy [3] were the first to obtain a vitreous V205, and later this was achieved by Dimitriev et al. [4], and Miroshnichenko and Klimashevski [5]. By applying if-sputtering, a new number of amorphous substances have been obtained, V205 included [6], which are designated according to the classification by Roy [7] as NCS (non-crystalline solid). Recently, in some works [8-10], glass-formation in pure V205 has again been discussed, in relation to the role of the small amount of water for glass-formation. The study of vanadate multi-component glasses has its beginnings in the investigations by Denton et al. [11], who defined the regions of glass-formation in several binary vanadate systems under ordinary conditions of quenching. A large part of the data obtained on the properties of glasses with the participation of V205 have been collected and described in the reference literature [12]. The interest in synthesizing similar glasses has been the result above all of the important electrical properties which they possess [13-16]. Certain new results for the glass-formation of selected compositions of the V205-MnO m binary system are presented in this communication. To obtain glasses from the melts, definite critical quenching rates [3,4,17] should be employed. Generally, they depend on the crystal structures and the structures of the melts. Since glass-formation is a rate phenomenon, it is natural to relate it to the nucleation frequency and to the subsequent rate of growth, which was done by Tamman for the first time, and by Turnbull and Cohen [18,19] in a much more explicit form. Several analytical relationships are obtained to calculate the minimal critical rates [20-22], which are chiefly applicable in the ease of pure substances and require a knowledge of the values of definite initial parameters with sufficient precision. As it is difficult to find such data for all the substances investigated, we preferred to choose an extreme quenching rate and this was attained by a roller technique, similar to the one described by Chen and Miller [23]. Glass-formation under identical extreme