Analytical Description of Degradation-Relaxation Transformations in Nanoinhomogeneous Spinel Ceramics

Abstract

Mathematical models of degradation-relaxation kinetics are considered for jammed thick-film systems composed of screen-printed spinel Cu0.1Ni0.1Co1.6Mn1.2O4 and conductive Ag or Ag-Pd alloys. Structurally intrinsic nanoinhomogeneous ceramics due to Ag and Ag-Pd diffusing agents embedded in a spinel phase environment are shown to define governing kinetics of thermally induced degradation under 170 °C obeying an obvious non-exponential behavior in a negative relative resistance drift. The characteristic stretched-to-compressed exponential crossover is detected for degradation-relaxation kinetics in thick-film systems with conductive contacts made of Ag-Pd and Ag alloys. Under essential migration of a conductive phase, Ag penetrates thick-film spinel ceramics via a considerable two-step diffusing process.

Kinetics models describing degradation-relaxation effects in nanoinhomogeneous substances

“…The both types of the studied nanoinhomogeneous substances demonstrate monotonically growing tendency in the RRD (in electrical resistance ∆R/R 0 ), this behavior having more threshold-like character in case of screen-printed Cu 0.1 Ni 0.1 Co 1.6 Mn 1.2 O 4 spinel ceramics with conductive Ag contacts as it shown previously in [7][8][9][10][11]. These dependences were examined through above RFs 1-5 to determine the best one describing this kinetics (the results for Cu 0.1 Ni 0.1 Co 1.6 Mn 1.2 O 4 thick films prepared with screen-printed Ag-Pd and Ag contacts are given in Tables 1 and 2, respectively).…”

“…In case of conductive Ag-Pd contact, the metallic Ag penetrates only in short pre-contact region. It is known that conductive material penetrating spinel ceramics reduces electrical resistivity, thus resulting in negative RRD for such thick-film systems [10,11]. This diffusive-related process is strongly thermally-activated, in contrast to own structural changes occurring in ceramics body, which produces rather positive feedback in the RRD due to increased defectiveness of spinel matrix [14].…”

“…These dependences were examined through above RFs 1-5 to determine the best one describing this kinetics (the results for Cu 0.1 Ni 0.1 Co 1.6 Mn 1.2 O 4 thick films prepared with screen-printed Ag-Pd and Ag contacts are given in Tables 1 and 2, respectively). (see table 2) can be presented by a well-known stretched-exponential RF 4 given by equation (7) The EDX study of Ag distribution profiles taken on fresh cut-sections of thick-film ceramics-Ag structures before and after degradation testing shows essential metallic penetration into ceramics [11].…”

“…_______________ * To whom any correspondence should be addressed. This work deals with specificity of thermally-induced electric degradation-relaxation phenomena revealed in heterogeneous jammed solid-state system composed of the same ceramics matrix with different types of diffusion agents (diffusants), exemplified by thick-film structures of spinel (Cu,Ni,Co,Mn) 3 O 4 manganites with screen-printed conductive layers composed of "pure" Ag and Agbased (made of Ag-Pd conductive paste C1216) alloys [7][8][9][10][11].…”

Hard Nanomaterials in Time of Viral Pandemics

“…Indeed, in vitro studies also evidenced a suppressive effect of acquired immune response of C 60 pyrrolidine tris-acid and fullerenol C 60 (OH) 36 . 145 The fullerenol had a dose-dependent effect on T cell receptor-mediated activation and antibody production by B cells under anti-CD40/IL-4 stimulation. However, the molecular mechanism is still unknown.…”