氧化铝粒度不同对铜氧化铝电触头材料性能的影响

(Ag , _ACuJ)-20%
polycrystalline phases. From the DSC measurements it is clear that a glass transition temperature around 327 K is exhibited by these specimens. The complex impedance studies carried out in the frequency range 65.5 kHz-1 Hz and transport number
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0167-2738/96/$15.00 Copyright 01996 Elsevier Science PII SO167-2738(96)00175-O
appropriate AgI-Cul solid solutions as dopant salts into a matrix of Ag,O-P,O,. Earlier investigations on the reciprocal role of Cu+ ions in the Ag,OB,O, matrix carried out in our laboratory have indicated the feasibility of obtaining high conductivity superionic solids in the mixed system CulAg,O-B,O, [6]. The present study deals with the synthesis and characterization of a variety of compositions in the new system 80% (Ag , _,CuJ)-20% (2Ag,O * P20s) where 0.05 5 x 5 0.25.
2.3. Complex impedance analysis and ionic transport number measurements The prepared samples were ground into fine powders and pressed with electrodes on either side under a pelletizing pressure of 4000 kg cm-’ to form circular pellets of 12 mm diameter. The electrodes consisted of silver metal powder mixed with the sample in the weight ratio 2:l in order to reduce interfacial resistance and also to maximise the interfacial surface area [7]. Electrical conductivity studies were carried out on all the pellet samples using a Solartron model 1254 four channel frequency response analyser and a Solar&on model 1286 electrochemical interface coupled with a BBC model B + microcomputer over the frequency range 65.5 kHz- 1 Hz. The experimental data obtained in the form of complex impedance plots i.e., plots of the imaginary part, Z”, against the real part Z of the impedance, Z were used for the estimation of the bulk resistance of the different samples. Ionic transport number measurements were made by employing e.m.f. technique. For this purpose, fine powders of each solid sample were pressed together with electrodes on either side under the pelletizing pressure of 4000 kg cm-‘. The negative electrode consisted of a mixture of silver powder and sample material in the weight ratio 2:l whereas the positive electrode was made from reagent grade iodine. The electrochemical cells thus fabricated had the configuration (-) Ag sample (2: l)/sample/I, (+). Silver ionic transport number in the case of individual composition was evaluated from the measured value of the open circuit voltage at room temperature (298 K).
2. Experimental 2.1. Preparation
of samples
Initially, polycrystalline samples of Ag , _,Cu,I (x = 0.05, 0.1, 0.15, 0.2 and 0.25‘) were prepared B.V.All rights ri. S.A. Suthunthiraruj
I Solid St&e Ionics
86-88
(1996)
459-462
using Analar grade AgNO,, CU(NO,)~. 2H,O and KI as starting materials. To start with, aqueous solutions of AgNO, and Cu(NO), .2H,O taken in appropriate amounts were mixed together. To this, an aqueous solution of KI was added in excess and the precipitate thus obtained was washed several times with double-distilled water and then with acetone. It was then filtered and dried in the dark at 373 K for nearly 3 h to obtain Ag, mLCu,I solid solutions for further studies. Commercially available Analar grade reagents of NH,H,PO, and Ag,O were employed as raw materials together with Ag,_,CuxI (x =0.05, 0.1, 0.15, 0.2 and 0.25) specimens, for the preparation of compositions of various the system 80% (Ag , -.,Cu,I)-20% (2Ag,O . P20,). NH,H,PO, was dried at 393 K just prior to use in view of the fact that NH,H,PO, on heating produces P?O, according to the reaction, 2NH,H2P0,“il;(P,0, + 3H20 + 3NH, (1)
Keywords:
(2Ag,O.
P,O,),
would possess
a
Superionic conduction; Mixed systems; Glass transition temperature
1. Introduction It is well-known that silver oxysalt matrices such as Ag,O-P,O,, Ag,O-Moo,, Ag,O-B,O, and Ag,O-V,O, in combination with Agl would offer a group of superionic glasses exhibiting Ag+ ionic conductivities of the order of 10-5-10-2 S cm-’ at 298 K [l-4]. Schmidt et al. [5] examined the mixed system Agl-Cul and found that solid solutions containing low copper content (i.e., 5 25 mol% Cul) would behave like a pure silver ionic conductor lying in a zone in which the crystal structure was that of Agl, favourable for the movement of silver ions. Hence, the present work has been undertaken with the ultimate aim of arriving at a new class of solid electrolytes for ambient conditions by employing