  It has been suggested that the Z-mode instability driven by energetic
electrons with a loss-cone type velocity distribution is one candidate process
behind the continuum and zebra pattern of solar type-IV radio bursts. Both the
temperature of background plasma ($T_0$) and the energy of energetic electrons
($v_e$) are considered to be important to the variation of the maximum growth
rate ($\gamma_{max}$). Here we present a detailed parameter study on the effect
of $T_0$ and $v_e$, within a regime of the frequency ratio ($10 \leq
\frac{\omega_{pe}}{\Omega_{ce}} \leq 30$). In addition to $\gamma_{max}$, we
also analyze the effect on the corresponding wave frequency ($\omega^r_{max}$)
and propagation angle ($\theta_{max}$). We find that (1) $\gamma_{max}$
in-general decreases with increasing $v_e$, while its variation with $T_0$ is
more complex depending on the exact value of $v_e$; (2) with increasing $T_0$
and $v_e$, $\omega^r_{max}$ presents step-wise profiles with jumps separated by
gradual or very-weak variations, and due to the warm-plasma effect on the wave
dispersion relation $\omega^r_{max}$ can vary within the hybrid band (the
harmonic band containing the upper hybrid frequency) and the band higher; (3)
the propagation is either perpendicular or quasi-perpendicular, and
$\theta_{max}$ presents variations in line with those of $\omega^r_{max}$, as
constrained by the resonance condition. We also examine the profiles of
$\gamma_{max}$ with $\frac{\omega_{pe}}{\Omega_{ce}}$ for different
combinations of $T_0$ and $v_e$ to clarify some earlier calculations which show
inconsistent results.
