Are of nga 
v Microscopic Characterisation of Manganese-Containing Oxide Ceramics for 
t Current Protection of Electric Circuits 
O. Shpotyuk'”, I. Hadzaman'?, O. Mrooz', A. Kovalskiy’, M. Vakiv' 
Institute of Materials, Scientific Research Company "Carat", Lviv, Ukraine 
2State Pedagogical University, Drohobych, Lviv Region, Ukraine 
Physics Institute, Pedagogical University, Czestochowa, Poland 
Introduction 
Transition metal oxides are the basic materials for NTC thermistors manufacturing (1-3). 
Application of multicomponent manganese-containing oxide ceramics of CuxNij.xyCozyMnayO4 
system for the development of NTC thermistors for current protection was reported by us earlier 
(3). The main advantage of these complex semiconducting materials is the possibility to obtain the 
wide series of thermistors with different exploitation parameters. Every chosen composition of 
ceramics must ensure the stable reproducible parameters of thermistors that depend on the 
technological features (sintering temperature, conditions of milling, firing of silver paste, etc.). So 
nd one of the main problems for multicomponent ceramic materials is to establish the optimum 
Pe technological conditions for the formation of solid solutions. The methods of microscopic 
characterisation and X-ray diffraction are used in this work with the aim to study the processes of 
a formation of ceramic matrix. 
antage of layered 
lications for this . 
son Experimental 
Investigated Cu,Nij.x.,CozyMnz.,O4 system (0.1<x<0.8; 0.1<y<0.9-x) was obtained as the result of 
+ ec 1 fe superposition of the regions of homogeneous solid solutions in quaternary Mn-Co-Ni-Cu oxide 
se system (Fig.1). The isolines of electrical conductivity for this system (Fig.2) are obtained by the 
ntering additive Ap . . . \ . 
in whe statistical-mathematical method of simplex matrices of the 4-fold D-optimum plan and verified by 
$e i Student criterion. Fourteen compositions inside of concentrational triangular restricted by 
eres 2 CuMn,O,. MnCo,04 and NiMn,O4 solid solutions were chosen as basic ones. 
The traditional technology was used for the preparation of ceramic specimens (1). Ceramic samples 
of various compositions were synthesized at three different sintering temperatures 7, corresponding 
to region 1: 7:=(0.5-0.75)T, (I, - melting point), region 2: 7,=(0.75-0.85)7,, and region 3: 
70.857. 
¢ 200 All samples were prepared in the form of disks. Investigations were carried out on the section 
metallographic specimens polished to mirror surfaces and thermochemically etched. 3% aqueous 
solutions of hydrochloric and orthophosphoric acids were used as etchants. Silver paste contacts 
were applied on the part of the samples. 
Phase composition, dimension and shape of grains were studied as visually as using "Neophot" 
optical metallographic microscope (x200-500 magnification). 
HZG-4a automatic powder diffractometer was used for X-ray diffraction investigations. 
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